1 /*
   2  * Copyright (c) 1999, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "jvm.h"
  26 #include "utilities/globalDefinitions.hpp"
  27 #include "runtime/frame.inline.hpp"
  28 #include "runtime/interfaceSupport.hpp"
  29 #include "runtime/os.hpp"
  30 #include "utilities/align.hpp"
  31 #include "utilities/macros.hpp"
  32 #include "utilities/vmError.hpp"
  33 
  34 #ifndef __APPLE__
  35 // POSIX unamed semaphores are not supported on OS X.
  36 #include "semaphore_posix.hpp"
  37 #endif
  38 
  39 #include <dlfcn.h>
  40 #include <pthread.h>
  41 #include <semaphore.h>
  42 #include <signal.h>
  43 #include <sys/resource.h>
  44 #include <sys/utsname.h>
  45 #include <time.h>
  46 #include <unistd.h>
  47 
  48 // Todo: provide a os::get_max_process_id() or similar. Number of processes
  49 // may have been configured, can be read more accurately from proc fs etc.
  50 #ifndef MAX_PID
  51 #define MAX_PID INT_MAX
  52 #endif
  53 #define IS_VALID_PID(p) (p > 0 && p < MAX_PID)
  54 
  55 // Check core dump limit and report possible place where core can be found
  56 void os::check_dump_limit(char* buffer, size_t bufferSize) {
  57   if (!FLAG_IS_DEFAULT(CreateCoredumpOnCrash) && !CreateCoredumpOnCrash) {
  58     jio_snprintf(buffer, bufferSize, "CreateCoredumpOnCrash is disabled from command line");
  59     VMError::record_coredump_status(buffer, false);
  60     return;
  61   }
  62 
  63   int n;
  64   struct rlimit rlim;
  65   bool success;
  66 
  67   char core_path[PATH_MAX];
  68   n = get_core_path(core_path, PATH_MAX);
  69 
  70   if (n <= 0) {
  71     jio_snprintf(buffer, bufferSize, "core.%d (may not exist)", current_process_id());
  72     success = true;
  73 #ifdef LINUX
  74   } else if (core_path[0] == '"') { // redirect to user process
  75     jio_snprintf(buffer, bufferSize, "Core dumps may be processed with %s", core_path);
  76     success = true;
  77 #endif
  78   } else if (getrlimit(RLIMIT_CORE, &rlim) != 0) {
  79     jio_snprintf(buffer, bufferSize, "%s (may not exist)", core_path);
  80     success = true;
  81   } else {
  82     switch(rlim.rlim_cur) {
  83       case RLIM_INFINITY:
  84         jio_snprintf(buffer, bufferSize, "%s", core_path);
  85         success = true;
  86         break;
  87       case 0:
  88         jio_snprintf(buffer, bufferSize, "Core dumps have been disabled. To enable core dumping, try \"ulimit -c unlimited\" before starting Java again");
  89         success = false;
  90         break;
  91       default:
  92         jio_snprintf(buffer, bufferSize, "%s (max size " UINT64_FORMAT " kB). To ensure a full core dump, try \"ulimit -c unlimited\" before starting Java again", core_path, uint64_t(rlim.rlim_cur) / 1024);
  93         success = true;
  94         break;
  95     }
  96   }
  97 
  98   VMError::record_coredump_status(buffer, success);
  99 }
 100 
 101 int os::get_native_stack(address* stack, int frames, int toSkip) {
 102   int frame_idx = 0;
 103   int num_of_frames;  // number of frames captured
 104   frame fr = os::current_frame();
 105   while (fr.pc() && frame_idx < frames) {
 106     if (toSkip > 0) {
 107       toSkip --;
 108     } else {
 109       stack[frame_idx ++] = fr.pc();
 110     }
 111     if (fr.fp() == NULL || fr.cb() != NULL ||
 112         fr.sender_pc() == NULL || os::is_first_C_frame(&fr)) break;
 113 
 114     if (fr.sender_pc() && !os::is_first_C_frame(&fr)) {
 115       fr = os::get_sender_for_C_frame(&fr);
 116     } else {
 117       break;
 118     }
 119   }
 120   num_of_frames = frame_idx;
 121   for (; frame_idx < frames; frame_idx ++) {
 122     stack[frame_idx] = NULL;
 123   }
 124 
 125   return num_of_frames;
 126 }
 127 
 128 
 129 bool os::unsetenv(const char* name) {
 130   assert(name != NULL, "Null pointer");
 131   return (::unsetenv(name) == 0);
 132 }
 133 
 134 int os::get_last_error() {
 135   return errno;
 136 }
 137 
 138 bool os::is_debugger_attached() {
 139   // not implemented
 140   return false;
 141 }
 142 
 143 void os::wait_for_keypress_at_exit(void) {
 144   // don't do anything on posix platforms
 145   return;
 146 }
 147 
 148 // Multiple threads can race in this code, and can remap over each other with MAP_FIXED,
 149 // so on posix, unmap the section at the start and at the end of the chunk that we mapped
 150 // rather than unmapping and remapping the whole chunk to get requested alignment.
 151 char* os::reserve_memory_aligned(size_t size, size_t alignment) {
 152   assert((alignment & (os::vm_allocation_granularity() - 1)) == 0,
 153       "Alignment must be a multiple of allocation granularity (page size)");
 154   assert((size & (alignment -1)) == 0, "size must be 'alignment' aligned");
 155 
 156   size_t extra_size = size + alignment;
 157   assert(extra_size >= size, "overflow, size is too large to allow alignment");
 158 
 159   char* extra_base = os::reserve_memory(extra_size, NULL, alignment);
 160 
 161   if (extra_base == NULL) {
 162     return NULL;
 163   }
 164 
 165   // Do manual alignment
 166   char* aligned_base = align_up(extra_base, alignment);
 167 
 168   // [  |                                       |  ]
 169   // ^ extra_base
 170   //    ^ extra_base + begin_offset == aligned_base
 171   //     extra_base + begin_offset + size       ^
 172   //                       extra_base + extra_size ^
 173   // |<>| == begin_offset
 174   //                              end_offset == |<>|
 175   size_t begin_offset = aligned_base - extra_base;
 176   size_t end_offset = (extra_base + extra_size) - (aligned_base + size);
 177 
 178   if (begin_offset > 0) {
 179       os::release_memory(extra_base, begin_offset);
 180   }
 181 
 182   if (end_offset > 0) {
 183       os::release_memory(extra_base + begin_offset + size, end_offset);
 184   }
 185 
 186   return aligned_base;
 187 }
 188 
 189 int os::log_vsnprintf(char* buf, size_t len, const char* fmt, va_list args) {
 190     return vsnprintf(buf, len, fmt, args);
 191 }
 192 
 193 int os::get_fileno(FILE* fp) {
 194   return NOT_AIX(::)fileno(fp);
 195 }
 196 
 197 struct tm* os::gmtime_pd(const time_t* clock, struct tm*  res) {
 198   return gmtime_r(clock, res);
 199 }
 200 
 201 void os::Posix::print_load_average(outputStream* st) {
 202   st->print("load average:");
 203   double loadavg[3];
 204   os::loadavg(loadavg, 3);
 205   st->print("%0.02f %0.02f %0.02f", loadavg[0], loadavg[1], loadavg[2]);
 206   st->cr();
 207 }
 208 
 209 void os::Posix::print_rlimit_info(outputStream* st) {
 210   st->print("rlimit:");
 211   struct rlimit rlim;
 212 
 213   st->print(" STACK ");
 214   getrlimit(RLIMIT_STACK, &rlim);
 215   if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
 216   else st->print(UINT64_FORMAT "k", uint64_t(rlim.rlim_cur) / 1024);
 217 
 218   st->print(", CORE ");
 219   getrlimit(RLIMIT_CORE, &rlim);
 220   if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
 221   else st->print(UINT64_FORMAT "k", uint64_t(rlim.rlim_cur) / 1024);
 222 
 223   // Isn't there on solaris
 224 #if defined(AIX)
 225   st->print(", NPROC ");
 226   st->print("%d", sysconf(_SC_CHILD_MAX));
 227 #elif !defined(SOLARIS)
 228   st->print(", NPROC ");
 229   getrlimit(RLIMIT_NPROC, &rlim);
 230   if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
 231   else st->print(UINT64_FORMAT, uint64_t(rlim.rlim_cur));
 232 #endif
 233 
 234   st->print(", NOFILE ");
 235   getrlimit(RLIMIT_NOFILE, &rlim);
 236   if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
 237   else st->print(UINT64_FORMAT, uint64_t(rlim.rlim_cur));
 238 
 239   st->print(", AS ");
 240   getrlimit(RLIMIT_AS, &rlim);
 241   if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
 242   else st->print(UINT64_FORMAT "k", uint64_t(rlim.rlim_cur) / 1024);
 243 
 244   st->print(", DATA ");
 245   getrlimit(RLIMIT_DATA, &rlim);
 246   if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
 247   else st->print(UINT64_FORMAT "k", uint64_t(rlim.rlim_cur) / 1024);
 248 
 249   st->print(", FSIZE ");
 250   getrlimit(RLIMIT_FSIZE, &rlim);
 251   if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
 252   else st->print(UINT64_FORMAT "k", uint64_t(rlim.rlim_cur) / 1024);
 253 
 254   st->cr();
 255 }
 256 
 257 void os::Posix::print_uname_info(outputStream* st) {
 258   // kernel
 259   st->print("uname:");
 260   struct utsname name;
 261   uname(&name);
 262   st->print("%s ", name.sysname);
 263 #ifdef ASSERT
 264   st->print("%s ", name.nodename);
 265 #endif
 266   st->print("%s ", name.release);
 267   st->print("%s ", name.version);
 268   st->print("%s", name.machine);
 269   st->cr();
 270 }
 271 
 272 bool os::get_host_name(char* buf, size_t buflen) {
 273   struct utsname name;
 274   uname(&name);
 275   jio_snprintf(buf, buflen, "%s", name.nodename);
 276   return true;
 277 }
 278 
 279 bool os::has_allocatable_memory_limit(julong* limit) {
 280   struct rlimit rlim;
 281   int getrlimit_res = getrlimit(RLIMIT_AS, &rlim);
 282   // if there was an error when calling getrlimit, assume that there is no limitation
 283   // on virtual memory.
 284   bool result;
 285   if ((getrlimit_res != 0) || (rlim.rlim_cur == RLIM_INFINITY)) {
 286     result = false;
 287   } else {
 288     *limit = (julong)rlim.rlim_cur;
 289     result = true;
 290   }
 291 #ifdef _LP64
 292   return result;
 293 #else
 294   // arbitrary virtual space limit for 32 bit Unices found by testing. If
 295   // getrlimit above returned a limit, bound it with this limit. Otherwise
 296   // directly use it.
 297   const julong max_virtual_limit = (julong)3800*M;
 298   if (result) {
 299     *limit = MIN2(*limit, max_virtual_limit);
 300   } else {
 301     *limit = max_virtual_limit;
 302   }
 303 
 304   // bound by actually allocatable memory. The algorithm uses two bounds, an
 305   // upper and a lower limit. The upper limit is the current highest amount of
 306   // memory that could not be allocated, the lower limit is the current highest
 307   // amount of memory that could be allocated.
 308   // The algorithm iteratively refines the result by halving the difference
 309   // between these limits, updating either the upper limit (if that value could
 310   // not be allocated) or the lower limit (if the that value could be allocated)
 311   // until the difference between these limits is "small".
 312 
 313   // the minimum amount of memory we care about allocating.
 314   const julong min_allocation_size = M;
 315 
 316   julong upper_limit = *limit;
 317 
 318   // first check a few trivial cases
 319   if (is_allocatable(upper_limit) || (upper_limit <= min_allocation_size)) {
 320     *limit = upper_limit;
 321   } else if (!is_allocatable(min_allocation_size)) {
 322     // we found that not even min_allocation_size is allocatable. Return it
 323     // anyway. There is no point to search for a better value any more.
 324     *limit = min_allocation_size;
 325   } else {
 326     // perform the binary search.
 327     julong lower_limit = min_allocation_size;
 328     while ((upper_limit - lower_limit) > min_allocation_size) {
 329       julong temp_limit = ((upper_limit - lower_limit) / 2) + lower_limit;
 330       temp_limit = align_down(temp_limit, min_allocation_size);
 331       if (is_allocatable(temp_limit)) {
 332         lower_limit = temp_limit;
 333       } else {
 334         upper_limit = temp_limit;
 335       }
 336     }
 337     *limit = lower_limit;
 338   }
 339   return true;
 340 #endif
 341 }
 342 
 343 const char* os::get_current_directory(char *buf, size_t buflen) {
 344   return getcwd(buf, buflen);
 345 }
 346 
 347 FILE* os::open(int fd, const char* mode) {
 348   return ::fdopen(fd, mode);
 349 }
 350 
 351 void os::flockfile(FILE* fp) {
 352   ::flockfile(fp);
 353 }
 354 
 355 void os::funlockfile(FILE* fp) {
 356   ::funlockfile(fp);
 357 }
 358 
 359 // Builds a platform dependent Agent_OnLoad_<lib_name> function name
 360 // which is used to find statically linked in agents.
 361 // Parameters:
 362 //            sym_name: Symbol in library we are looking for
 363 //            lib_name: Name of library to look in, NULL for shared libs.
 364 //            is_absolute_path == true if lib_name is absolute path to agent
 365 //                                     such as "/a/b/libL.so"
 366 //            == false if only the base name of the library is passed in
 367 //               such as "L"
 368 char* os::build_agent_function_name(const char *sym_name, const char *lib_name,
 369                                     bool is_absolute_path) {
 370   char *agent_entry_name;
 371   size_t len;
 372   size_t name_len;
 373   size_t prefix_len = strlen(JNI_LIB_PREFIX);
 374   size_t suffix_len = strlen(JNI_LIB_SUFFIX);
 375   const char *start;
 376 
 377   if (lib_name != NULL) {
 378     name_len = strlen(lib_name);
 379     if (is_absolute_path) {
 380       // Need to strip path, prefix and suffix
 381       if ((start = strrchr(lib_name, *os::file_separator())) != NULL) {
 382         lib_name = ++start;
 383       }
 384       if (strlen(lib_name) <= (prefix_len + suffix_len)) {
 385         return NULL;
 386       }
 387       lib_name += prefix_len;
 388       name_len = strlen(lib_name) - suffix_len;
 389     }
 390   }
 391   len = (lib_name != NULL ? name_len : 0) + strlen(sym_name) + 2;
 392   agent_entry_name = NEW_C_HEAP_ARRAY_RETURN_NULL(char, len, mtThread);
 393   if (agent_entry_name == NULL) {
 394     return NULL;
 395   }
 396   strcpy(agent_entry_name, sym_name);
 397   if (lib_name != NULL) {
 398     strcat(agent_entry_name, "_");
 399     strncat(agent_entry_name, lib_name, name_len);
 400   }
 401   return agent_entry_name;
 402 }
 403 
 404 int os::sleep(Thread* thread, jlong millis, bool interruptible) {
 405   assert(thread == Thread::current(),  "thread consistency check");
 406 
 407   ParkEvent * const slp = thread->_SleepEvent ;
 408   slp->reset() ;
 409   OrderAccess::fence() ;
 410 
 411   if (interruptible) {
 412     jlong prevtime = javaTimeNanos();
 413 
 414     for (;;) {
 415       if (os::is_interrupted(thread, true)) {
 416         return OS_INTRPT;
 417       }
 418 
 419       jlong newtime = javaTimeNanos();
 420 
 421       if (newtime - prevtime < 0) {
 422         // time moving backwards, should only happen if no monotonic clock
 423         // not a guarantee() because JVM should not abort on kernel/glibc bugs
 424         assert(!os::supports_monotonic_clock(), "unexpected time moving backwards detected in os::sleep(interruptible)");
 425       } else {
 426         millis -= (newtime - prevtime) / NANOSECS_PER_MILLISEC;
 427       }
 428 
 429       if (millis <= 0) {
 430         return OS_OK;
 431       }
 432 
 433       prevtime = newtime;
 434 
 435       {
 436         assert(thread->is_Java_thread(), "sanity check");
 437         JavaThread *jt = (JavaThread *) thread;
 438         ThreadBlockInVM tbivm(jt);
 439         OSThreadWaitState osts(jt->osthread(), false /* not Object.wait() */);
 440 
 441         jt->set_suspend_equivalent();
 442         // cleared by handle_special_suspend_equivalent_condition() or
 443         // java_suspend_self() via check_and_wait_while_suspended()
 444 
 445         slp->park(millis);
 446 
 447         // were we externally suspended while we were waiting?
 448         jt->check_and_wait_while_suspended();
 449       }
 450     }
 451   } else {
 452     OSThreadWaitState osts(thread->osthread(), false /* not Object.wait() */);
 453     jlong prevtime = javaTimeNanos();
 454 
 455     for (;;) {
 456       // It'd be nice to avoid the back-to-back javaTimeNanos() calls on
 457       // the 1st iteration ...
 458       jlong newtime = javaTimeNanos();
 459 
 460       if (newtime - prevtime < 0) {
 461         // time moving backwards, should only happen if no monotonic clock
 462         // not a guarantee() because JVM should not abort on kernel/glibc bugs
 463         assert(!os::supports_monotonic_clock(), "unexpected time moving backwards detected on os::sleep(!interruptible)");
 464       } else {
 465         millis -= (newtime - prevtime) / NANOSECS_PER_MILLISEC;
 466       }
 467 
 468       if (millis <= 0) break ;
 469 
 470       prevtime = newtime;
 471       slp->park(millis);
 472     }
 473     return OS_OK ;
 474   }
 475 }
 476 
 477 ////////////////////////////////////////////////////////////////////////////////
 478 // interrupt support
 479 
 480 void os::interrupt(Thread* thread) {
 481   assert(Thread::current() == thread || Threads_lock->owned_by_self(),
 482     "possibility of dangling Thread pointer");
 483 
 484   OSThread* osthread = thread->osthread();
 485 
 486   if (!osthread->interrupted()) {
 487     osthread->set_interrupted(true);
 488     // More than one thread can get here with the same value of osthread,
 489     // resulting in multiple notifications.  We do, however, want the store
 490     // to interrupted() to be visible to other threads before we execute unpark().
 491     OrderAccess::fence();
 492     ParkEvent * const slp = thread->_SleepEvent ;
 493     if (slp != NULL) slp->unpark() ;
 494   }
 495 
 496   // For JSR166. Unpark even if interrupt status already was set
 497   if (thread->is_Java_thread())
 498     ((JavaThread*)thread)->parker()->unpark();
 499 
 500   ParkEvent * ev = thread->_ParkEvent ;
 501   if (ev != NULL) ev->unpark() ;
 502 
 503 }
 504 
 505 bool os::is_interrupted(Thread* thread, bool clear_interrupted) {
 506   assert(Thread::current() == thread || Threads_lock->owned_by_self(),
 507     "possibility of dangling Thread pointer");
 508 
 509   OSThread* osthread = thread->osthread();
 510 
 511   bool interrupted = osthread->interrupted();
 512 
 513   // NOTE that since there is no "lock" around the interrupt and
 514   // is_interrupted operations, there is the possibility that the
 515   // interrupted flag (in osThread) will be "false" but that the
 516   // low-level events will be in the signaled state. This is
 517   // intentional. The effect of this is that Object.wait() and
 518   // LockSupport.park() will appear to have a spurious wakeup, which
 519   // is allowed and not harmful, and the possibility is so rare that
 520   // it is not worth the added complexity to add yet another lock.
 521   // For the sleep event an explicit reset is performed on entry
 522   // to os::sleep, so there is no early return. It has also been
 523   // recommended not to put the interrupted flag into the "event"
 524   // structure because it hides the issue.
 525   if (interrupted && clear_interrupted) {
 526     osthread->set_interrupted(false);
 527     // consider thread->_SleepEvent->reset() ... optional optimization
 528   }
 529 
 530   return interrupted;
 531 }
 532 
 533 
 534 
 535 static const struct {
 536   int sig; const char* name;
 537 }
 538  g_signal_info[] =
 539   {
 540   {  SIGABRT,     "SIGABRT" },
 541 #ifdef SIGAIO
 542   {  SIGAIO,      "SIGAIO" },
 543 #endif
 544   {  SIGALRM,     "SIGALRM" },
 545 #ifdef SIGALRM1
 546   {  SIGALRM1,    "SIGALRM1" },
 547 #endif
 548   {  SIGBUS,      "SIGBUS" },
 549 #ifdef SIGCANCEL
 550   {  SIGCANCEL,   "SIGCANCEL" },
 551 #endif
 552   {  SIGCHLD,     "SIGCHLD" },
 553 #ifdef SIGCLD
 554   {  SIGCLD,      "SIGCLD" },
 555 #endif
 556   {  SIGCONT,     "SIGCONT" },
 557 #ifdef SIGCPUFAIL
 558   {  SIGCPUFAIL,  "SIGCPUFAIL" },
 559 #endif
 560 #ifdef SIGDANGER
 561   {  SIGDANGER,   "SIGDANGER" },
 562 #endif
 563 #ifdef SIGDIL
 564   {  SIGDIL,      "SIGDIL" },
 565 #endif
 566 #ifdef SIGEMT
 567   {  SIGEMT,      "SIGEMT" },
 568 #endif
 569   {  SIGFPE,      "SIGFPE" },
 570 #ifdef SIGFREEZE
 571   {  SIGFREEZE,   "SIGFREEZE" },
 572 #endif
 573 #ifdef SIGGFAULT
 574   {  SIGGFAULT,   "SIGGFAULT" },
 575 #endif
 576 #ifdef SIGGRANT
 577   {  SIGGRANT,    "SIGGRANT" },
 578 #endif
 579   {  SIGHUP,      "SIGHUP" },
 580   {  SIGILL,      "SIGILL" },
 581   {  SIGINT,      "SIGINT" },
 582 #ifdef SIGIO
 583   {  SIGIO,       "SIGIO" },
 584 #endif
 585 #ifdef SIGIOINT
 586   {  SIGIOINT,    "SIGIOINT" },
 587 #endif
 588 #ifdef SIGIOT
 589 // SIGIOT is there for BSD compatibility, but on most Unices just a
 590 // synonym for SIGABRT. The result should be "SIGABRT", not
 591 // "SIGIOT".
 592 #if (SIGIOT != SIGABRT )
 593   {  SIGIOT,      "SIGIOT" },
 594 #endif
 595 #endif
 596 #ifdef SIGKAP
 597   {  SIGKAP,      "SIGKAP" },
 598 #endif
 599   {  SIGKILL,     "SIGKILL" },
 600 #ifdef SIGLOST
 601   {  SIGLOST,     "SIGLOST" },
 602 #endif
 603 #ifdef SIGLWP
 604   {  SIGLWP,      "SIGLWP" },
 605 #endif
 606 #ifdef SIGLWPTIMER
 607   {  SIGLWPTIMER, "SIGLWPTIMER" },
 608 #endif
 609 #ifdef SIGMIGRATE
 610   {  SIGMIGRATE,  "SIGMIGRATE" },
 611 #endif
 612 #ifdef SIGMSG
 613   {  SIGMSG,      "SIGMSG" },
 614 #endif
 615   {  SIGPIPE,     "SIGPIPE" },
 616 #ifdef SIGPOLL
 617   {  SIGPOLL,     "SIGPOLL" },
 618 #endif
 619 #ifdef SIGPRE
 620   {  SIGPRE,      "SIGPRE" },
 621 #endif
 622   {  SIGPROF,     "SIGPROF" },
 623 #ifdef SIGPTY
 624   {  SIGPTY,      "SIGPTY" },
 625 #endif
 626 #ifdef SIGPWR
 627   {  SIGPWR,      "SIGPWR" },
 628 #endif
 629   {  SIGQUIT,     "SIGQUIT" },
 630 #ifdef SIGRECONFIG
 631   {  SIGRECONFIG, "SIGRECONFIG" },
 632 #endif
 633 #ifdef SIGRECOVERY
 634   {  SIGRECOVERY, "SIGRECOVERY" },
 635 #endif
 636 #ifdef SIGRESERVE
 637   {  SIGRESERVE,  "SIGRESERVE" },
 638 #endif
 639 #ifdef SIGRETRACT
 640   {  SIGRETRACT,  "SIGRETRACT" },
 641 #endif
 642 #ifdef SIGSAK
 643   {  SIGSAK,      "SIGSAK" },
 644 #endif
 645   {  SIGSEGV,     "SIGSEGV" },
 646 #ifdef SIGSOUND
 647   {  SIGSOUND,    "SIGSOUND" },
 648 #endif
 649 #ifdef SIGSTKFLT
 650   {  SIGSTKFLT,    "SIGSTKFLT" },
 651 #endif
 652   {  SIGSTOP,     "SIGSTOP" },
 653   {  SIGSYS,      "SIGSYS" },
 654 #ifdef SIGSYSERROR
 655   {  SIGSYSERROR, "SIGSYSERROR" },
 656 #endif
 657 #ifdef SIGTALRM
 658   {  SIGTALRM,    "SIGTALRM" },
 659 #endif
 660   {  SIGTERM,     "SIGTERM" },
 661 #ifdef SIGTHAW
 662   {  SIGTHAW,     "SIGTHAW" },
 663 #endif
 664   {  SIGTRAP,     "SIGTRAP" },
 665 #ifdef SIGTSTP
 666   {  SIGTSTP,     "SIGTSTP" },
 667 #endif
 668   {  SIGTTIN,     "SIGTTIN" },
 669   {  SIGTTOU,     "SIGTTOU" },
 670 #ifdef SIGURG
 671   {  SIGURG,      "SIGURG" },
 672 #endif
 673   {  SIGUSR1,     "SIGUSR1" },
 674   {  SIGUSR2,     "SIGUSR2" },
 675 #ifdef SIGVIRT
 676   {  SIGVIRT,     "SIGVIRT" },
 677 #endif
 678   {  SIGVTALRM,   "SIGVTALRM" },
 679 #ifdef SIGWAITING
 680   {  SIGWAITING,  "SIGWAITING" },
 681 #endif
 682 #ifdef SIGWINCH
 683   {  SIGWINCH,    "SIGWINCH" },
 684 #endif
 685 #ifdef SIGWINDOW
 686   {  SIGWINDOW,   "SIGWINDOW" },
 687 #endif
 688   {  SIGXCPU,     "SIGXCPU" },
 689   {  SIGXFSZ,     "SIGXFSZ" },
 690 #ifdef SIGXRES
 691   {  SIGXRES,     "SIGXRES" },
 692 #endif
 693   { -1, NULL }
 694 };
 695 
 696 // Returned string is a constant. For unknown signals "UNKNOWN" is returned.
 697 const char* os::Posix::get_signal_name(int sig, char* out, size_t outlen) {
 698 
 699   const char* ret = NULL;
 700 
 701 #ifdef SIGRTMIN
 702   if (sig >= SIGRTMIN && sig <= SIGRTMAX) {
 703     if (sig == SIGRTMIN) {
 704       ret = "SIGRTMIN";
 705     } else if (sig == SIGRTMAX) {
 706       ret = "SIGRTMAX";
 707     } else {
 708       jio_snprintf(out, outlen, "SIGRTMIN+%d", sig - SIGRTMIN);
 709       return out;
 710     }
 711   }
 712 #endif
 713 
 714   if (sig > 0) {
 715     for (int idx = 0; g_signal_info[idx].sig != -1; idx ++) {
 716       if (g_signal_info[idx].sig == sig) {
 717         ret = g_signal_info[idx].name;
 718         break;
 719       }
 720     }
 721   }
 722 
 723   if (!ret) {
 724     if (!is_valid_signal(sig)) {
 725       ret = "INVALID";
 726     } else {
 727       ret = "UNKNOWN";
 728     }
 729   }
 730 
 731   if (out && outlen > 0) {
 732     strncpy(out, ret, outlen);
 733     out[outlen - 1] = '\0';
 734   }
 735   return out;
 736 }
 737 
 738 int os::Posix::get_signal_number(const char* signal_name) {
 739   char tmp[30];
 740   const char* s = signal_name;
 741   if (s[0] != 'S' || s[1] != 'I' || s[2] != 'G') {
 742     jio_snprintf(tmp, sizeof(tmp), "SIG%s", signal_name);
 743     s = tmp;
 744   }
 745   for (int idx = 0; g_signal_info[idx].sig != -1; idx ++) {
 746     if (strcmp(g_signal_info[idx].name, s) == 0) {
 747       return g_signal_info[idx].sig;
 748     }
 749   }
 750   return -1;
 751 }
 752 
 753 int os::get_signal_number(const char* signal_name) {
 754   return os::Posix::get_signal_number(signal_name);
 755 }
 756 
 757 // Returns true if signal number is valid.
 758 bool os::Posix::is_valid_signal(int sig) {
 759   // MacOS not really POSIX compliant: sigaddset does not return
 760   // an error for invalid signal numbers. However, MacOS does not
 761   // support real time signals and simply seems to have just 33
 762   // signals with no holes in the signal range.
 763 #ifdef __APPLE__
 764   return sig >= 1 && sig < NSIG;
 765 #else
 766   // Use sigaddset to check for signal validity.
 767   sigset_t set;
 768   sigemptyset(&set);
 769   if (sigaddset(&set, sig) == -1 && errno == EINVAL) {
 770     return false;
 771   }
 772   return true;
 773 #endif
 774 }
 775 
 776 // Returns:
 777 // NULL for an invalid signal number
 778 // "SIG<num>" for a valid but unknown signal number
 779 // signal name otherwise.
 780 const char* os::exception_name(int sig, char* buf, size_t size) {
 781   if (!os::Posix::is_valid_signal(sig)) {
 782     return NULL;
 783   }
 784   const char* const name = os::Posix::get_signal_name(sig, buf, size);
 785   if (strcmp(name, "UNKNOWN") == 0) {
 786     jio_snprintf(buf, size, "SIG%d", sig);
 787   }
 788   return buf;
 789 }
 790 
 791 #define NUM_IMPORTANT_SIGS 32
 792 // Returns one-line short description of a signal set in a user provided buffer.
 793 const char* os::Posix::describe_signal_set_short(const sigset_t* set, char* buffer, size_t buf_size) {
 794   assert(buf_size == (NUM_IMPORTANT_SIGS + 1), "wrong buffer size");
 795   // Note: for shortness, just print out the first 32. That should
 796   // cover most of the useful ones, apart from realtime signals.
 797   for (int sig = 1; sig <= NUM_IMPORTANT_SIGS; sig++) {
 798     const int rc = sigismember(set, sig);
 799     if (rc == -1 && errno == EINVAL) {
 800       buffer[sig-1] = '?';
 801     } else {
 802       buffer[sig-1] = rc == 0 ? '0' : '1';
 803     }
 804   }
 805   buffer[NUM_IMPORTANT_SIGS] = 0;
 806   return buffer;
 807 }
 808 
 809 // Prints one-line description of a signal set.
 810 void os::Posix::print_signal_set_short(outputStream* st, const sigset_t* set) {
 811   char buf[NUM_IMPORTANT_SIGS + 1];
 812   os::Posix::describe_signal_set_short(set, buf, sizeof(buf));
 813   st->print("%s", buf);
 814 }
 815 
 816 // Writes one-line description of a combination of sigaction.sa_flags into a user
 817 // provided buffer. Returns that buffer.
 818 const char* os::Posix::describe_sa_flags(int flags, char* buffer, size_t size) {
 819   char* p = buffer;
 820   size_t remaining = size;
 821   bool first = true;
 822   int idx = 0;
 823 
 824   assert(buffer, "invalid argument");
 825 
 826   if (size == 0) {
 827     return buffer;
 828   }
 829 
 830   strncpy(buffer, "none", size);
 831 
 832   const struct {
 833     // NB: i is an unsigned int here because SA_RESETHAND is on some
 834     // systems 0x80000000, which is implicitly unsigned.  Assignining
 835     // it to an int field would be an overflow in unsigned-to-signed
 836     // conversion.
 837     unsigned int i;
 838     const char* s;
 839   } flaginfo [] = {
 840     { SA_NOCLDSTOP, "SA_NOCLDSTOP" },
 841     { SA_ONSTACK,   "SA_ONSTACK"   },
 842     { SA_RESETHAND, "SA_RESETHAND" },
 843     { SA_RESTART,   "SA_RESTART"   },
 844     { SA_SIGINFO,   "SA_SIGINFO"   },
 845     { SA_NOCLDWAIT, "SA_NOCLDWAIT" },
 846     { SA_NODEFER,   "SA_NODEFER"   },
 847 #ifdef AIX
 848     { SA_ONSTACK,   "SA_ONSTACK"   },
 849     { SA_OLDSTYLE,  "SA_OLDSTYLE"  },
 850 #endif
 851     { 0, NULL }
 852   };
 853 
 854   for (idx = 0; flaginfo[idx].s && remaining > 1; idx++) {
 855     if (flags & flaginfo[idx].i) {
 856       if (first) {
 857         jio_snprintf(p, remaining, "%s", flaginfo[idx].s);
 858         first = false;
 859       } else {
 860         jio_snprintf(p, remaining, "|%s", flaginfo[idx].s);
 861       }
 862       const size_t len = strlen(p);
 863       p += len;
 864       remaining -= len;
 865     }
 866   }
 867 
 868   buffer[size - 1] = '\0';
 869 
 870   return buffer;
 871 }
 872 
 873 // Prints one-line description of a combination of sigaction.sa_flags.
 874 void os::Posix::print_sa_flags(outputStream* st, int flags) {
 875   char buffer[0x100];
 876   os::Posix::describe_sa_flags(flags, buffer, sizeof(buffer));
 877   st->print("%s", buffer);
 878 }
 879 
 880 // Helper function for os::Posix::print_siginfo_...():
 881 // return a textual description for signal code.
 882 struct enum_sigcode_desc_t {
 883   const char* s_name;
 884   const char* s_desc;
 885 };
 886 
 887 static bool get_signal_code_description(const siginfo_t* si, enum_sigcode_desc_t* out) {
 888 
 889   const struct {
 890     int sig; int code; const char* s_code; const char* s_desc;
 891   } t1 [] = {
 892     { SIGILL,  ILL_ILLOPC,   "ILL_ILLOPC",   "Illegal opcode." },
 893     { SIGILL,  ILL_ILLOPN,   "ILL_ILLOPN",   "Illegal operand." },
 894     { SIGILL,  ILL_ILLADR,   "ILL_ILLADR",   "Illegal addressing mode." },
 895     { SIGILL,  ILL_ILLTRP,   "ILL_ILLTRP",   "Illegal trap." },
 896     { SIGILL,  ILL_PRVOPC,   "ILL_PRVOPC",   "Privileged opcode." },
 897     { SIGILL,  ILL_PRVREG,   "ILL_PRVREG",   "Privileged register." },
 898     { SIGILL,  ILL_COPROC,   "ILL_COPROC",   "Coprocessor error." },
 899     { SIGILL,  ILL_BADSTK,   "ILL_BADSTK",   "Internal stack error." },
 900 #if defined(IA64) && defined(LINUX)
 901     { SIGILL,  ILL_BADIADDR, "ILL_BADIADDR", "Unimplemented instruction address" },
 902     { SIGILL,  ILL_BREAK,    "ILL_BREAK",    "Application Break instruction" },
 903 #endif
 904     { SIGFPE,  FPE_INTDIV,   "FPE_INTDIV",   "Integer divide by zero." },
 905     { SIGFPE,  FPE_INTOVF,   "FPE_INTOVF",   "Integer overflow." },
 906     { SIGFPE,  FPE_FLTDIV,   "FPE_FLTDIV",   "Floating-point divide by zero." },
 907     { SIGFPE,  FPE_FLTOVF,   "FPE_FLTOVF",   "Floating-point overflow." },
 908     { SIGFPE,  FPE_FLTUND,   "FPE_FLTUND",   "Floating-point underflow." },
 909     { SIGFPE,  FPE_FLTRES,   "FPE_FLTRES",   "Floating-point inexact result." },
 910     { SIGFPE,  FPE_FLTINV,   "FPE_FLTINV",   "Invalid floating-point operation." },
 911     { SIGFPE,  FPE_FLTSUB,   "FPE_FLTSUB",   "Subscript out of range." },
 912     { SIGSEGV, SEGV_MAPERR,  "SEGV_MAPERR",  "Address not mapped to object." },
 913     { SIGSEGV, SEGV_ACCERR,  "SEGV_ACCERR",  "Invalid permissions for mapped object." },
 914 #ifdef AIX
 915     // no explanation found what keyerr would be
 916     { SIGSEGV, SEGV_KEYERR,  "SEGV_KEYERR",  "key error" },
 917 #endif
 918 #if defined(IA64) && !defined(AIX)
 919     { SIGSEGV, SEGV_PSTKOVF, "SEGV_PSTKOVF", "Paragraph stack overflow" },
 920 #endif
 921 #if defined(__sparc) && defined(SOLARIS)
 922 // define Solaris Sparc M7 ADI SEGV signals
 923 #if !defined(SEGV_ACCADI)
 924 #define SEGV_ACCADI 3
 925 #endif
 926     { SIGSEGV, SEGV_ACCADI,  "SEGV_ACCADI",  "ADI not enabled for mapped object." },
 927 #if !defined(SEGV_ACCDERR)
 928 #define SEGV_ACCDERR 4
 929 #endif
 930     { SIGSEGV, SEGV_ACCDERR, "SEGV_ACCDERR", "ADI disrupting exception." },
 931 #if !defined(SEGV_ACCPERR)
 932 #define SEGV_ACCPERR 5
 933 #endif
 934     { SIGSEGV, SEGV_ACCPERR, "SEGV_ACCPERR", "ADI precise exception." },
 935 #endif // defined(__sparc) && defined(SOLARIS)
 936     { SIGBUS,  BUS_ADRALN,   "BUS_ADRALN",   "Invalid address alignment." },
 937     { SIGBUS,  BUS_ADRERR,   "BUS_ADRERR",   "Nonexistent physical address." },
 938     { SIGBUS,  BUS_OBJERR,   "BUS_OBJERR",   "Object-specific hardware error." },
 939     { SIGTRAP, TRAP_BRKPT,   "TRAP_BRKPT",   "Process breakpoint." },
 940     { SIGTRAP, TRAP_TRACE,   "TRAP_TRACE",   "Process trace trap." },
 941     { SIGCHLD, CLD_EXITED,   "CLD_EXITED",   "Child has exited." },
 942     { SIGCHLD, CLD_KILLED,   "CLD_KILLED",   "Child has terminated abnormally and did not create a core file." },
 943     { SIGCHLD, CLD_DUMPED,   "CLD_DUMPED",   "Child has terminated abnormally and created a core file." },
 944     { SIGCHLD, CLD_TRAPPED,  "CLD_TRAPPED",  "Traced child has trapped." },
 945     { SIGCHLD, CLD_STOPPED,  "CLD_STOPPED",  "Child has stopped." },
 946     { SIGCHLD, CLD_CONTINUED,"CLD_CONTINUED","Stopped child has continued." },
 947 #ifdef SIGPOLL
 948     { SIGPOLL, POLL_OUT,     "POLL_OUT",     "Output buffers available." },
 949     { SIGPOLL, POLL_MSG,     "POLL_MSG",     "Input message available." },
 950     { SIGPOLL, POLL_ERR,     "POLL_ERR",     "I/O error." },
 951     { SIGPOLL, POLL_PRI,     "POLL_PRI",     "High priority input available." },
 952     { SIGPOLL, POLL_HUP,     "POLL_HUP",     "Device disconnected. [Option End]" },
 953 #endif
 954     { -1, -1, NULL, NULL }
 955   };
 956 
 957   // Codes valid in any signal context.
 958   const struct {
 959     int code; const char* s_code; const char* s_desc;
 960   } t2 [] = {
 961     { SI_USER,      "SI_USER",     "Signal sent by kill()." },
 962     { SI_QUEUE,     "SI_QUEUE",    "Signal sent by the sigqueue()." },
 963     { SI_TIMER,     "SI_TIMER",    "Signal generated by expiration of a timer set by timer_settime()." },
 964     { SI_ASYNCIO,   "SI_ASYNCIO",  "Signal generated by completion of an asynchronous I/O request." },
 965     { SI_MESGQ,     "SI_MESGQ",    "Signal generated by arrival of a message on an empty message queue." },
 966     // Linux specific
 967 #ifdef SI_TKILL
 968     { SI_TKILL,     "SI_TKILL",    "Signal sent by tkill (pthread_kill)" },
 969 #endif
 970 #ifdef SI_DETHREAD
 971     { SI_DETHREAD,  "SI_DETHREAD", "Signal sent by execve() killing subsidiary threads" },
 972 #endif
 973 #ifdef SI_KERNEL
 974     { SI_KERNEL,    "SI_KERNEL",   "Signal sent by kernel." },
 975 #endif
 976 #ifdef SI_SIGIO
 977     { SI_SIGIO,     "SI_SIGIO",    "Signal sent by queued SIGIO" },
 978 #endif
 979 
 980 #ifdef AIX
 981     { SI_UNDEFINED, "SI_UNDEFINED","siginfo contains partial information" },
 982     { SI_EMPTY,     "SI_EMPTY",    "siginfo contains no useful information" },
 983 #endif
 984 
 985 #ifdef __sun
 986     { SI_NOINFO,    "SI_NOINFO",   "No signal information" },
 987     { SI_RCTL,      "SI_RCTL",     "kernel generated signal via rctl action" },
 988     { SI_LWP,       "SI_LWP",      "Signal sent via lwp_kill" },
 989 #endif
 990 
 991     { -1, NULL, NULL }
 992   };
 993 
 994   const char* s_code = NULL;
 995   const char* s_desc = NULL;
 996 
 997   for (int i = 0; t1[i].sig != -1; i ++) {
 998     if (t1[i].sig == si->si_signo && t1[i].code == si->si_code) {
 999       s_code = t1[i].s_code;
1000       s_desc = t1[i].s_desc;
1001       break;
1002     }
1003   }
1004 
1005   if (s_code == NULL) {
1006     for (int i = 0; t2[i].s_code != NULL; i ++) {
1007       if (t2[i].code == si->si_code) {
1008         s_code = t2[i].s_code;
1009         s_desc = t2[i].s_desc;
1010       }
1011     }
1012   }
1013 
1014   if (s_code == NULL) {
1015     out->s_name = "unknown";
1016     out->s_desc = "unknown";
1017     return false;
1018   }
1019 
1020   out->s_name = s_code;
1021   out->s_desc = s_desc;
1022 
1023   return true;
1024 }
1025 
1026 void os::print_siginfo(outputStream* os, const void* si0) {
1027 
1028   const siginfo_t* const si = (const siginfo_t*) si0;
1029 
1030   char buf[20];
1031   os->print("siginfo:");
1032 
1033   if (!si) {
1034     os->print(" <null>");
1035     return;
1036   }
1037 
1038   const int sig = si->si_signo;
1039 
1040   os->print(" si_signo: %d (%s)", sig, os::Posix::get_signal_name(sig, buf, sizeof(buf)));
1041 
1042   enum_sigcode_desc_t ed;
1043   get_signal_code_description(si, &ed);
1044   os->print(", si_code: %d (%s)", si->si_code, ed.s_name);
1045 
1046   if (si->si_errno) {
1047     os->print(", si_errno: %d", si->si_errno);
1048   }
1049 
1050   // Output additional information depending on the signal code.
1051 
1052   // Note: Many implementations lump si_addr, si_pid, si_uid etc. together as unions,
1053   // so it depends on the context which member to use. For synchronous error signals,
1054   // we print si_addr, unless the signal was sent by another process or thread, in
1055   // which case we print out pid or tid of the sender.
1056   if (si->si_code == SI_USER || si->si_code == SI_QUEUE) {
1057     const pid_t pid = si->si_pid;
1058     os->print(", si_pid: %ld", (long) pid);
1059     if (IS_VALID_PID(pid)) {
1060       const pid_t me = getpid();
1061       if (me == pid) {
1062         os->print(" (current process)");
1063       }
1064     } else {
1065       os->print(" (invalid)");
1066     }
1067     os->print(", si_uid: %ld", (long) si->si_uid);
1068     if (sig == SIGCHLD) {
1069       os->print(", si_status: %d", si->si_status);
1070     }
1071   } else if (sig == SIGSEGV || sig == SIGBUS || sig == SIGILL ||
1072              sig == SIGTRAP || sig == SIGFPE) {
1073     os->print(", si_addr: " PTR_FORMAT, p2i(si->si_addr));
1074 #ifdef SIGPOLL
1075   } else if (sig == SIGPOLL) {
1076     os->print(", si_band: %ld", si->si_band);
1077 #endif
1078   }
1079 
1080 }
1081 
1082 int os::Posix::unblock_thread_signal_mask(const sigset_t *set) {
1083   return pthread_sigmask(SIG_UNBLOCK, set, NULL);
1084 }
1085 
1086 address os::Posix::ucontext_get_pc(const ucontext_t* ctx) {
1087 #if defined(AIX)
1088    return Aix::ucontext_get_pc(ctx);
1089 #elif defined(BSD)
1090    return Bsd::ucontext_get_pc(ctx);
1091 #elif defined(LINUX)
1092    return Linux::ucontext_get_pc(ctx);
1093 #elif defined(SOLARIS)
1094    return Solaris::ucontext_get_pc(ctx);
1095 #else
1096    VMError::report_and_die("unimplemented ucontext_get_pc");
1097 #endif
1098 }
1099 
1100 void os::Posix::ucontext_set_pc(ucontext_t* ctx, address pc) {
1101 #if defined(AIX)
1102    Aix::ucontext_set_pc(ctx, pc);
1103 #elif defined(BSD)
1104    Bsd::ucontext_set_pc(ctx, pc);
1105 #elif defined(LINUX)
1106    Linux::ucontext_set_pc(ctx, pc);
1107 #elif defined(SOLARIS)
1108    Solaris::ucontext_set_pc(ctx, pc);
1109 #else
1110    VMError::report_and_die("unimplemented ucontext_get_pc");
1111 #endif
1112 }
1113 
1114 char* os::Posix::describe_pthread_attr(char* buf, size_t buflen, const pthread_attr_t* attr) {
1115   size_t stack_size = 0;
1116   size_t guard_size = 0;
1117   int detachstate = 0;
1118   pthread_attr_getstacksize(attr, &stack_size);
1119   pthread_attr_getguardsize(attr, &guard_size);
1120   // Work around linux NPTL implementation error, see also os::create_thread() in os_linux.cpp.
1121   LINUX_ONLY(stack_size -= guard_size);
1122   pthread_attr_getdetachstate(attr, &detachstate);
1123   jio_snprintf(buf, buflen, "stacksize: " SIZE_FORMAT "k, guardsize: " SIZE_FORMAT "k, %s",
1124     stack_size / 1024, guard_size / 1024,
1125     (detachstate == PTHREAD_CREATE_DETACHED ? "detached" : "joinable"));
1126   return buf;
1127 }
1128 
1129 char* os::Posix::realpath(const char* filename, char* outbuf, size_t outbuflen) {
1130 
1131   if (filename == NULL || outbuf == NULL || outbuflen < 1) {
1132     assert(false, "os::Posix::realpath: invalid arguments.");
1133     errno = EINVAL;
1134     return NULL;
1135   }
1136 
1137   char* result = NULL;
1138 
1139   // This assumes platform realpath() is implemented according to POSIX.1-2008.
1140   // POSIX.1-2008 allows to specify NULL for the output buffer, in which case
1141   // output buffer is dynamically allocated and must be ::free()'d by the caller.
1142   char* p = ::realpath(filename, NULL);
1143   if (p != NULL) {
1144     if (strlen(p) < outbuflen) {
1145       strcpy(outbuf, p);
1146       result = outbuf;
1147     } else {
1148       errno = ENAMETOOLONG;
1149     }
1150     ::free(p); // *not* os::free
1151   } else {
1152     // Fallback for platforms struggling with modern Posix standards (AIX 5.3, 6.1). If realpath
1153     // returns EINVAL, this may indicate that realpath is not POSIX.1-2008 compatible and
1154     // that it complains about the NULL we handed down as user buffer.
1155     // In this case, use the user provided buffer but at least check whether realpath caused
1156     // a memory overwrite.
1157     if (errno == EINVAL) {
1158       outbuf[outbuflen - 1] = '\0';
1159       p = ::realpath(filename, outbuf);
1160       if (p != NULL) {
1161         guarantee(outbuf[outbuflen - 1] == '\0', "realpath buffer overwrite detected.");
1162         result = p;
1163       }
1164     }
1165   }
1166   return result;
1167 
1168 }
1169 
1170 
1171 // Check minimum allowable stack sizes for thread creation and to initialize
1172 // the java system classes, including StackOverflowError - depends on page
1173 // size.
1174 // The space needed for frames during startup is platform dependent. It
1175 // depends on word size, platform calling conventions, C frame layout and
1176 // interpreter/C1/C2 design decisions. Therefore this is given in a
1177 // platform (os/cpu) dependent constant.
1178 // To this, space for guard mechanisms is added, which depends on the
1179 // page size which again depends on the concrete system the VM is running
1180 // on. Space for libc guard pages is not included in this size.
1181 jint os::Posix::set_minimum_stack_sizes() {
1182   size_t os_min_stack_allowed = SOLARIS_ONLY(thr_min_stack()) NOT_SOLARIS(PTHREAD_STACK_MIN);
1183 
1184   _java_thread_min_stack_allowed = _java_thread_min_stack_allowed +
1185                                    JavaThread::stack_guard_zone_size() +
1186                                    JavaThread::stack_shadow_zone_size();
1187 
1188   _java_thread_min_stack_allowed = align_up(_java_thread_min_stack_allowed, vm_page_size());
1189   _java_thread_min_stack_allowed = MAX2(_java_thread_min_stack_allowed, os_min_stack_allowed);
1190 
1191   size_t stack_size_in_bytes = ThreadStackSize * K;
1192   if (stack_size_in_bytes != 0 &&
1193       stack_size_in_bytes < _java_thread_min_stack_allowed) {
1194     // The '-Xss' and '-XX:ThreadStackSize=N' options both set
1195     // ThreadStackSize so we go with "Java thread stack size" instead
1196     // of "ThreadStackSize" to be more friendly.
1197     tty->print_cr("\nThe Java thread stack size specified is too small. "
1198                   "Specify at least " SIZE_FORMAT "k",
1199                   _java_thread_min_stack_allowed / K);
1200     return JNI_ERR;
1201   }
1202 
1203   // Make the stack size a multiple of the page size so that
1204   // the yellow/red zones can be guarded.
1205   JavaThread::set_stack_size_at_create(align_up(stack_size_in_bytes, vm_page_size()));
1206 
1207   // Reminder: a compiler thread is a Java thread.
1208   _compiler_thread_min_stack_allowed = _compiler_thread_min_stack_allowed +
1209                                        JavaThread::stack_guard_zone_size() +
1210                                        JavaThread::stack_shadow_zone_size();
1211 
1212   _compiler_thread_min_stack_allowed = align_up(_compiler_thread_min_stack_allowed, vm_page_size());
1213   _compiler_thread_min_stack_allowed = MAX2(_compiler_thread_min_stack_allowed, os_min_stack_allowed);
1214 
1215   stack_size_in_bytes = CompilerThreadStackSize * K;
1216   if (stack_size_in_bytes != 0 &&
1217       stack_size_in_bytes < _compiler_thread_min_stack_allowed) {
1218     tty->print_cr("\nThe CompilerThreadStackSize specified is too small. "
1219                   "Specify at least " SIZE_FORMAT "k",
1220                   _compiler_thread_min_stack_allowed / K);
1221     return JNI_ERR;
1222   }
1223 
1224   _vm_internal_thread_min_stack_allowed = align_up(_vm_internal_thread_min_stack_allowed, vm_page_size());
1225   _vm_internal_thread_min_stack_allowed = MAX2(_vm_internal_thread_min_stack_allowed, os_min_stack_allowed);
1226 
1227   stack_size_in_bytes = VMThreadStackSize * K;
1228   if (stack_size_in_bytes != 0 &&
1229       stack_size_in_bytes < _vm_internal_thread_min_stack_allowed) {
1230     tty->print_cr("\nThe VMThreadStackSize specified is too small. "
1231                   "Specify at least " SIZE_FORMAT "k",
1232                   _vm_internal_thread_min_stack_allowed / K);
1233     return JNI_ERR;
1234   }
1235   return JNI_OK;
1236 }
1237 
1238 // Called when creating the thread.  The minimum stack sizes have already been calculated
1239 size_t os::Posix::get_initial_stack_size(ThreadType thr_type, size_t req_stack_size) {
1240   size_t stack_size;
1241   if (req_stack_size == 0) {
1242     stack_size = default_stack_size(thr_type);
1243   } else {
1244     stack_size = req_stack_size;
1245   }
1246 
1247   switch (thr_type) {
1248   case os::java_thread:
1249     // Java threads use ThreadStackSize which default value can be
1250     // changed with the flag -Xss
1251     if (req_stack_size == 0 && JavaThread::stack_size_at_create() > 0) {
1252       // no requested size and we have a more specific default value
1253       stack_size = JavaThread::stack_size_at_create();
1254     }
1255     stack_size = MAX2(stack_size,
1256                       _java_thread_min_stack_allowed);
1257     break;
1258   case os::compiler_thread:
1259     if (req_stack_size == 0 && CompilerThreadStackSize > 0) {
1260       // no requested size and we have a more specific default value
1261       stack_size = (size_t)(CompilerThreadStackSize * K);
1262     }
1263     stack_size = MAX2(stack_size,
1264                       _compiler_thread_min_stack_allowed);
1265     break;
1266   case os::vm_thread:
1267   case os::pgc_thread:
1268   case os::cgc_thread:
1269   case os::watcher_thread:
1270   default:  // presume the unknown thr_type is a VM internal
1271     if (req_stack_size == 0 && VMThreadStackSize > 0) {
1272       // no requested size and we have a more specific default value
1273       stack_size = (size_t)(VMThreadStackSize * K);
1274     }
1275 
1276     stack_size = MAX2(stack_size,
1277                       _vm_internal_thread_min_stack_allowed);
1278     break;
1279   }
1280 
1281   // pthread_attr_setstacksize() may require that the size be rounded up to the OS page size.
1282   // Be careful not to round up to 0. Align down in that case.
1283   if (stack_size <= SIZE_MAX - vm_page_size()) {
1284     stack_size = align_up(stack_size, vm_page_size());
1285   } else {
1286     stack_size = align_down(stack_size, vm_page_size());
1287   }
1288 
1289   return stack_size;
1290 }
1291 
1292 Thread* os::ThreadCrashProtection::_protected_thread = NULL;
1293 os::ThreadCrashProtection* os::ThreadCrashProtection::_crash_protection = NULL;
1294 volatile intptr_t os::ThreadCrashProtection::_crash_mux = 0;
1295 
1296 os::ThreadCrashProtection::ThreadCrashProtection() {
1297 }
1298 
1299 /*
1300  * See the caveats for this class in os_posix.hpp
1301  * Protects the callback call so that SIGSEGV / SIGBUS jumps back into this
1302  * method and returns false. If none of the signals are raised, returns true.
1303  * The callback is supposed to provide the method that should be protected.
1304  */
1305 bool os::ThreadCrashProtection::call(os::CrashProtectionCallback& cb) {
1306   sigset_t saved_sig_mask;
1307 
1308   Thread::muxAcquire(&_crash_mux, "CrashProtection");
1309 
1310   _protected_thread = Thread::current_or_null();
1311   assert(_protected_thread != NULL, "Cannot crash protect a NULL thread");
1312 
1313   // we cannot rely on sigsetjmp/siglongjmp to save/restore the signal mask
1314   // since on at least some systems (OS X) siglongjmp will restore the mask
1315   // for the process, not the thread
1316   pthread_sigmask(0, NULL, &saved_sig_mask);
1317   if (sigsetjmp(_jmpbuf, 0) == 0) {
1318     // make sure we can see in the signal handler that we have crash protection
1319     // installed
1320     _crash_protection = this;
1321     cb.call();
1322     // and clear the crash protection
1323     _crash_protection = NULL;
1324     _protected_thread = NULL;
1325     Thread::muxRelease(&_crash_mux);
1326     return true;
1327   }
1328   // this happens when we siglongjmp() back
1329   pthread_sigmask(SIG_SETMASK, &saved_sig_mask, NULL);
1330   _crash_protection = NULL;
1331   _protected_thread = NULL;
1332   Thread::muxRelease(&_crash_mux);
1333   return false;
1334 }
1335 
1336 void os::ThreadCrashProtection::restore() {
1337   assert(_crash_protection != NULL, "must have crash protection");
1338   siglongjmp(_jmpbuf, 1);
1339 }
1340 
1341 void os::ThreadCrashProtection::check_crash_protection(int sig,
1342     Thread* thread) {
1343 
1344   if (thread != NULL &&
1345       thread == _protected_thread &&
1346       _crash_protection != NULL) {
1347 
1348     if (sig == SIGSEGV || sig == SIGBUS) {
1349       _crash_protection->restore();
1350     }
1351   }
1352 }
1353 
1354 #define check_with_errno(check_type, cond, msg)                             \
1355   do {                                                                      \
1356     int err = errno;                                                        \
1357     check_type(cond, "%s; error='%s' (errno=%s)", msg, os::strerror(err),   \
1358                os::errno_name(err));                                        \
1359 } while (false)
1360 
1361 #define assert_with_errno(cond, msg)    check_with_errno(assert, cond, msg)
1362 #define guarantee_with_errno(cond, msg) check_with_errno(guarantee, cond, msg)
1363 
1364 // POSIX unamed semaphores are not supported on OS X.
1365 #ifndef __APPLE__
1366 
1367 PosixSemaphore::PosixSemaphore(uint value) {
1368   int ret = sem_init(&_semaphore, 0, value);
1369 
1370   guarantee_with_errno(ret == 0, "Failed to initialize semaphore");
1371 }
1372 
1373 PosixSemaphore::~PosixSemaphore() {
1374   sem_destroy(&_semaphore);
1375 }
1376 
1377 void PosixSemaphore::signal(uint count) {
1378   for (uint i = 0; i < count; i++) {
1379     int ret = sem_post(&_semaphore);
1380 
1381     assert_with_errno(ret == 0, "sem_post failed");
1382   }
1383 }
1384 
1385 void PosixSemaphore::wait() {
1386   int ret;
1387 
1388   do {
1389     ret = sem_wait(&_semaphore);
1390   } while (ret != 0 && errno == EINTR);
1391 
1392   assert_with_errno(ret == 0, "sem_wait failed");
1393 }
1394 
1395 bool PosixSemaphore::trywait() {
1396   int ret;
1397 
1398   do {
1399     ret = sem_trywait(&_semaphore);
1400   } while (ret != 0 && errno == EINTR);
1401 
1402   assert_with_errno(ret == 0 || errno == EAGAIN, "trywait failed");
1403 
1404   return ret == 0;
1405 }
1406 
1407 bool PosixSemaphore::timedwait(struct timespec ts) {
1408   while (true) {
1409     int result = sem_timedwait(&_semaphore, &ts);
1410     if (result == 0) {
1411       return true;
1412     } else if (errno == EINTR) {
1413       continue;
1414     } else if (errno == ETIMEDOUT) {
1415       return false;
1416     } else {
1417       assert_with_errno(false, "timedwait failed");
1418       return false;
1419     }
1420   }
1421 }
1422 
1423 #endif // __APPLE__
1424 
1425 
1426 // Shared pthread_mutex/cond based PlatformEvent implementation.
1427 // Not currently usable by Solaris.
1428 
1429 #ifndef SOLARIS
1430 
1431 // Shared condattr object for use with relative timed-waits. Will be associated
1432 // with CLOCK_MONOTONIC if available to avoid issues with time-of-day changes,
1433 // but otherwise whatever default is used by the platform - generally the
1434 // time-of-day clock.
1435 static pthread_condattr_t _condAttr[1];
1436 
1437 // Shared mutexattr to explicitly set the type to PTHREAD_MUTEX_NORMAL as not
1438 // all systems (e.g. FreeBSD) map the default to "normal".
1439 static pthread_mutexattr_t _mutexAttr[1];
1440 
1441 // common basic initialization that is always supported
1442 static void pthread_init_common(void) {
1443   int status;
1444   if ((status = pthread_condattr_init(_condAttr)) != 0) {
1445     fatal("pthread_condattr_init: %s", os::strerror(status));
1446   }
1447   if ((status = pthread_mutexattr_init(_mutexAttr)) != 0) {
1448     fatal("pthread_mutexattr_init: %s", os::strerror(status));
1449   }
1450   if ((status = pthread_mutexattr_settype(_mutexAttr, PTHREAD_MUTEX_NORMAL)) != 0) {
1451     fatal("pthread_mutexattr_settype: %s", os::strerror(status));
1452   }
1453 }
1454 
1455 // Not all POSIX types and API's are available on all notionally "posix"
1456 // platforms. If we have build-time support then we will check for actual
1457 // runtime support via dlopen/dlsym lookup. This allows for running on an
1458 // older OS version compared to the build platform. But if there is no
1459 // build time support then there cannot be any runtime support as we do not
1460 // know what the runtime types would be (for example clockid_t might be an
1461 // int or int64_t).
1462 //
1463 #ifdef SUPPORTS_CLOCK_MONOTONIC
1464 
1465 // This means we have clockid_t, clock_gettime et al and CLOCK_MONOTONIC
1466 
1467 static int (*_clock_gettime)(clockid_t, struct timespec *);
1468 static int (*_pthread_condattr_setclock)(pthread_condattr_t *, clockid_t);
1469 
1470 static bool _use_clock_monotonic_condattr;
1471 
1472 // Determine what POSIX API's are present and do appropriate
1473 // configuration.
1474 void os::Posix::init(void) {
1475 
1476   // NOTE: no logging available when this is called. Put logging
1477   // statements in init_2().
1478 
1479   // Copied from os::Linux::clock_init(). The duplication is temporary.
1480 
1481   // 1. Check for CLOCK_MONOTONIC support.
1482 
1483   void* handle = NULL;
1484 
1485   // For linux we need librt, for other OS we can find
1486   // this function in regular libc.
1487 #ifdef NEEDS_LIBRT
1488   // We do dlopen's in this particular order due to bug in linux
1489   // dynamic loader (see 6348968) leading to crash on exit.
1490   handle = dlopen("librt.so.1", RTLD_LAZY);
1491   if (handle == NULL) {
1492     handle = dlopen("librt.so", RTLD_LAZY);
1493   }
1494 #endif
1495 
1496   if (handle == NULL) {
1497     handle = RTLD_DEFAULT;
1498   }
1499 
1500   _clock_gettime = NULL;
1501 
1502   int (*clock_getres_func)(clockid_t, struct timespec*) =
1503     (int(*)(clockid_t, struct timespec*))dlsym(handle, "clock_getres");
1504   int (*clock_gettime_func)(clockid_t, struct timespec*) =
1505     (int(*)(clockid_t, struct timespec*))dlsym(handle, "clock_gettime");
1506   if (clock_getres_func != NULL && clock_gettime_func != NULL) {
1507     // We assume that if both clock_gettime and clock_getres support
1508     // CLOCK_MONOTONIC then the OS provides true high-res monotonic clock.
1509     struct timespec res;
1510     struct timespec tp;
1511     if (clock_getres_func(CLOCK_MONOTONIC, &res) == 0 &&
1512         clock_gettime_func(CLOCK_MONOTONIC, &tp) == 0) {
1513       // Yes, monotonic clock is supported.
1514       _clock_gettime = clock_gettime_func;
1515     } else {
1516 #ifdef NEEDS_LIBRT
1517       // Close librt if there is no monotonic clock.
1518       if (handle != RTLD_DEFAULT) {
1519         dlclose(handle);
1520       }
1521 #endif
1522     }
1523   }
1524 
1525   // 2. Check for pthread_condattr_setclock support.
1526 
1527   _pthread_condattr_setclock = NULL;
1528 
1529   // libpthread is already loaded.
1530   int (*condattr_setclock_func)(pthread_condattr_t*, clockid_t) =
1531     (int (*)(pthread_condattr_t*, clockid_t))dlsym(RTLD_DEFAULT,
1532                                                    "pthread_condattr_setclock");
1533   if (condattr_setclock_func != NULL) {
1534     _pthread_condattr_setclock = condattr_setclock_func;
1535   }
1536 
1537   // Now do general initialization.
1538 
1539   pthread_init_common();
1540 
1541   int status;
1542   if (_pthread_condattr_setclock != NULL && _clock_gettime != NULL) {
1543     if ((status = _pthread_condattr_setclock(_condAttr, CLOCK_MONOTONIC)) != 0) {
1544       if (status == EINVAL) {
1545         _use_clock_monotonic_condattr = false;
1546         warning("Unable to use monotonic clock with relative timed-waits" \
1547                 " - changes to the time-of-day clock may have adverse affects");
1548       } else {
1549         fatal("pthread_condattr_setclock: %s", os::strerror(status));
1550       }
1551     } else {
1552       _use_clock_monotonic_condattr = true;
1553     }
1554   } else {
1555     _use_clock_monotonic_condattr = false;
1556   }
1557 }
1558 
1559 void os::Posix::init_2(void) {
1560   log_info(os)("Use of CLOCK_MONOTONIC is%s supported",
1561                (_clock_gettime != NULL ? "" : " not"));
1562   log_info(os)("Use of pthread_condattr_setclock is%s supported",
1563                (_pthread_condattr_setclock != NULL ? "" : " not"));
1564   log_info(os)("Relative timed-wait using pthread_cond_timedwait is associated with %s",
1565                _use_clock_monotonic_condattr ? "CLOCK_MONOTONIC" : "the default clock");
1566 }
1567 
1568 #else // !SUPPORTS_CLOCK_MONOTONIC
1569 
1570 void os::Posix::init(void) {
1571   pthread_init_common();
1572 }
1573 
1574 void os::Posix::init_2(void) {
1575   log_info(os)("Use of CLOCK_MONOTONIC is not supported");
1576   log_info(os)("Use of pthread_condattr_setclock is not supported");
1577   log_info(os)("Relative timed-wait using pthread_cond_timedwait is associated with the default clock");
1578 }
1579 
1580 #endif // SUPPORTS_CLOCK_MONOTONIC
1581 
1582 os::PlatformEvent::PlatformEvent() {
1583   int status = pthread_cond_init(_cond, _condAttr);
1584   assert_status(status == 0, status, "cond_init");
1585   status = pthread_mutex_init(_mutex, _mutexAttr);
1586   assert_status(status == 0, status, "mutex_init");
1587   _event   = 0;
1588   _nParked = 0;
1589 }
1590 
1591 // Utility to convert the given timeout to an absolute timespec
1592 // (based on the appropriate clock) to use with pthread_cond_timewait.
1593 // The clock queried here must be the clock used to manage the
1594 // timeout of the condition variable.
1595 //
1596 // The passed in timeout value is either a relative time in nanoseconds
1597 // or an absolute time in milliseconds. A relative timeout will be
1598 // associated with CLOCK_MONOTONIC if available; otherwise, or if absolute,
1599 // the default time-of-day clock will be used.
1600 
1601 // Given time is a 64-bit value and the time_t used in the timespec is
1602 // sometimes a signed-32-bit value we have to watch for overflow if times
1603 // way in the future are given. Further on Solaris versions
1604 // prior to 10 there is a restriction (see cond_timedwait) that the specified
1605 // number of seconds, in abstime, is less than current_time + 100000000.
1606 // As it will be over 20 years before "now + 100000000" will overflow we can
1607 // ignore overflow and just impose a hard-limit on seconds using the value
1608 // of "now + 100000000". This places a limit on the timeout of about 3.17
1609 // years from "now".
1610 //
1611 #define MAX_SECS 100000000
1612 
1613 // Calculate a new absolute time that is "timeout" nanoseconds from "now".
1614 // "unit" indicates the unit of "now_part_sec" (may be nanos or micros depending
1615 // on which clock is being used).
1616 static void calc_rel_time(timespec* abstime, jlong timeout, jlong now_sec,
1617                           jlong now_part_sec, jlong unit) {
1618   time_t max_secs = now_sec + MAX_SECS;
1619 
1620   jlong seconds = timeout / NANOUNITS;
1621   timeout %= NANOUNITS; // remaining nanos
1622 
1623   if (seconds >= MAX_SECS) {
1624     // More seconds than we can add, so pin to max_secs.
1625     abstime->tv_sec = max_secs;
1626     abstime->tv_nsec = 0;
1627   } else {
1628     abstime->tv_sec = now_sec  + seconds;
1629     long nanos = (now_part_sec * (NANOUNITS / unit)) + timeout;
1630     if (nanos >= NANOUNITS) { // overflow
1631       abstime->tv_sec += 1;
1632       nanos -= NANOUNITS;
1633     }
1634     abstime->tv_nsec = nanos;
1635   }
1636 }
1637 
1638 // Unpack the given deadline in milliseconds since the epoch, into the given timespec.
1639 // The current time in seconds is also passed in to enforce an upper bound as discussed above.
1640 static void unpack_abs_time(timespec* abstime, jlong deadline, jlong now_sec) {
1641   time_t max_secs = now_sec + MAX_SECS;
1642 
1643   jlong seconds = deadline / MILLIUNITS;
1644   jlong millis = deadline % MILLIUNITS;
1645 
1646   if (seconds >= max_secs) {
1647     // Absolute seconds exceeds allowed max, so pin to max_secs.
1648     abstime->tv_sec = max_secs;
1649     abstime->tv_nsec = 0;
1650   } else {
1651     abstime->tv_sec = seconds;
1652     abstime->tv_nsec = millis * (NANOUNITS / MILLIUNITS);
1653   }
1654 }
1655 
1656 static void to_abstime(timespec* abstime, jlong timeout, bool isAbsolute) {
1657   DEBUG_ONLY(int max_secs = MAX_SECS;)
1658 
1659   if (timeout < 0) {
1660     timeout = 0;
1661   }
1662 
1663 #ifdef SUPPORTS_CLOCK_MONOTONIC
1664 
1665   if (_use_clock_monotonic_condattr && !isAbsolute) {
1666     struct timespec now;
1667     int status = _clock_gettime(CLOCK_MONOTONIC, &now);
1668     assert_status(status == 0, status, "clock_gettime");
1669     calc_rel_time(abstime, timeout, now.tv_sec, now.tv_nsec, NANOUNITS);
1670     DEBUG_ONLY(max_secs += now.tv_sec;)
1671   } else {
1672 
1673 #else
1674 
1675   { // Match the block scope.
1676 
1677 #endif // SUPPORTS_CLOCK_MONOTONIC
1678 
1679     // Time-of-day clock is all we can reliably use.
1680     struct timeval now;
1681     int status = gettimeofday(&now, NULL);
1682     assert_status(status == 0, errno, "gettimeofday");
1683     if (isAbsolute) {
1684       unpack_abs_time(abstime, timeout, now.tv_sec);
1685     } else {
1686       calc_rel_time(abstime, timeout, now.tv_sec, now.tv_usec, MICROUNITS);
1687     }
1688     DEBUG_ONLY(max_secs += now.tv_sec;)
1689   }
1690 
1691   assert(abstime->tv_sec >= 0, "tv_sec < 0");
1692   assert(abstime->tv_sec <= max_secs, "tv_sec > max_secs");
1693   assert(abstime->tv_nsec >= 0, "tv_nsec < 0");
1694   assert(abstime->tv_nsec < NANOUNITS, "tv_nsec >= NANOUNITS");
1695 }
1696 
1697 // PlatformEvent
1698 //
1699 // Assumption:
1700 //    Only one parker can exist on an event, which is why we allocate
1701 //    them per-thread. Multiple unparkers can coexist.
1702 //
1703 // _event serves as a restricted-range semaphore.
1704 //   -1 : thread is blocked, i.e. there is a waiter
1705 //    0 : neutral: thread is running or ready,
1706 //        could have been signaled after a wait started
1707 //    1 : signaled - thread is running or ready
1708 //
1709 //    Having three states allows for some detection of bad usage - see
1710 //    comments on unpark().
1711 
1712 void os::PlatformEvent::park() {       // AKA "down()"
1713   // Transitions for _event:
1714   //   -1 => -1 : illegal
1715   //    1 =>  0 : pass - return immediately
1716   //    0 => -1 : block; then set _event to 0 before returning
1717 
1718   // Invariant: Only the thread associated with the PlatformEvent
1719   // may call park().
1720   assert(_nParked == 0, "invariant");
1721 
1722   int v;
1723 
1724   // atomically decrement _event
1725   for (;;) {
1726     v = _event;
1727     if (Atomic::cmpxchg(v - 1, &_event, v) == v) break;
1728   }
1729   guarantee(v >= 0, "invariant");
1730 
1731   if (v == 0) { // Do this the hard way by blocking ...
1732     int status = pthread_mutex_lock(_mutex);
1733     assert_status(status == 0, status, "mutex_lock");
1734     guarantee(_nParked == 0, "invariant");
1735     ++_nParked;
1736     while (_event < 0) {
1737       // OS-level "spurious wakeups" are ignored
1738       status = pthread_cond_wait(_cond, _mutex);
1739       assert_status(status == 0, status, "cond_wait");
1740     }
1741     --_nParked;
1742 
1743     _event = 0;
1744     status = pthread_mutex_unlock(_mutex);
1745     assert_status(status == 0, status, "mutex_unlock");
1746     // Paranoia to ensure our locked and lock-free paths interact
1747     // correctly with each other.
1748     OrderAccess::fence();
1749   }
1750   guarantee(_event >= 0, "invariant");
1751 }
1752 
1753 int os::PlatformEvent::park(jlong millis) {
1754   // Transitions for _event:
1755   //   -1 => -1 : illegal
1756   //    1 =>  0 : pass - return immediately
1757   //    0 => -1 : block; then set _event to 0 before returning
1758 
1759   // Invariant: Only the thread associated with the Event/PlatformEvent
1760   // may call park().
1761   assert(_nParked == 0, "invariant");
1762 
1763   int v;
1764   // atomically decrement _event
1765   for (;;) {
1766     v = _event;
1767     if (Atomic::cmpxchg(v - 1, &_event, v) == v) break;
1768   }
1769   guarantee(v >= 0, "invariant");
1770 
1771   if (v == 0) { // Do this the hard way by blocking ...
1772     struct timespec abst;
1773     // We have to watch for overflow when converting millis to nanos,
1774     // but if millis is that large then we will end up limiting to
1775     // MAX_SECS anyway, so just do that here.
1776     if (millis / MILLIUNITS > MAX_SECS) {
1777       millis = jlong(MAX_SECS) * MILLIUNITS;
1778     }
1779     to_abstime(&abst, millis * (NANOUNITS / MILLIUNITS), false);
1780 
1781     int ret = OS_TIMEOUT;
1782     int status = pthread_mutex_lock(_mutex);
1783     assert_status(status == 0, status, "mutex_lock");
1784     guarantee(_nParked == 0, "invariant");
1785     ++_nParked;
1786 
1787     while (_event < 0) {
1788       status = pthread_cond_timedwait(_cond, _mutex, &abst);
1789       assert_status(status == 0 || status == ETIMEDOUT,
1790                     status, "cond_timedwait");
1791       // OS-level "spurious wakeups" are ignored unless the archaic
1792       // FilterSpuriousWakeups is set false. That flag should be obsoleted.
1793       if (!FilterSpuriousWakeups) break;
1794       if (status == ETIMEDOUT) break;
1795     }
1796     --_nParked;
1797 
1798     if (_event >= 0) {
1799       ret = OS_OK;
1800     }
1801 
1802     _event = 0;
1803     status = pthread_mutex_unlock(_mutex);
1804     assert_status(status == 0, status, "mutex_unlock");
1805     // Paranoia to ensure our locked and lock-free paths interact
1806     // correctly with each other.
1807     OrderAccess::fence();
1808     return ret;
1809   }
1810   return OS_OK;
1811 }
1812 
1813 void os::PlatformEvent::unpark() {
1814   // Transitions for _event:
1815   //    0 => 1 : just return
1816   //    1 => 1 : just return
1817   //   -1 => either 0 or 1; must signal target thread
1818   //         That is, we can safely transition _event from -1 to either
1819   //         0 or 1.
1820   // See also: "Semaphores in Plan 9" by Mullender & Cox
1821   //
1822   // Note: Forcing a transition from "-1" to "1" on an unpark() means
1823   // that it will take two back-to-back park() calls for the owning
1824   // thread to block. This has the benefit of forcing a spurious return
1825   // from the first park() call after an unpark() call which will help
1826   // shake out uses of park() and unpark() without checking state conditions
1827   // properly. This spurious return doesn't manifest itself in any user code
1828   // but only in the correctly written condition checking loops of ObjectMonitor,
1829   // Mutex/Monitor, Thread::muxAcquire and os::sleep
1830 
1831   if (Atomic::xchg(1, &_event) >= 0) return;
1832 
1833   int status = pthread_mutex_lock(_mutex);
1834   assert_status(status == 0, status, "mutex_lock");
1835   int anyWaiters = _nParked;
1836   assert(anyWaiters == 0 || anyWaiters == 1, "invariant");
1837   status = pthread_mutex_unlock(_mutex);
1838   assert_status(status == 0, status, "mutex_unlock");
1839 
1840   // Note that we signal() *after* dropping the lock for "immortal" Events.
1841   // This is safe and avoids a common class of futile wakeups.  In rare
1842   // circumstances this can cause a thread to return prematurely from
1843   // cond_{timed}wait() but the spurious wakeup is benign and the victim
1844   // will simply re-test the condition and re-park itself.
1845   // This provides particular benefit if the underlying platform does not
1846   // provide wait morphing.
1847 
1848   if (anyWaiters != 0) {
1849     status = pthread_cond_signal(_cond);
1850     assert_status(status == 0, status, "cond_signal");
1851   }
1852 }
1853 
1854 // JSR166 support
1855 
1856  os::PlatformParker::PlatformParker() {
1857   int status;
1858   status = pthread_cond_init(&_cond[REL_INDEX], _condAttr);
1859   assert_status(status == 0, status, "cond_init rel");
1860   status = pthread_cond_init(&_cond[ABS_INDEX], NULL);
1861   assert_status(status == 0, status, "cond_init abs");
1862   status = pthread_mutex_init(_mutex, _mutexAttr);
1863   assert_status(status == 0, status, "mutex_init");
1864   _cur_index = -1; // mark as unused
1865 }
1866 
1867 // Parker::park decrements count if > 0, else does a condvar wait.  Unpark
1868 // sets count to 1 and signals condvar.  Only one thread ever waits
1869 // on the condvar. Contention seen when trying to park implies that someone
1870 // is unparking you, so don't wait. And spurious returns are fine, so there
1871 // is no need to track notifications.
1872 
1873 void Parker::park(bool isAbsolute, jlong time) {
1874 
1875   // Optional fast-path check:
1876   // Return immediately if a permit is available.
1877   // We depend on Atomic::xchg() having full barrier semantics
1878   // since we are doing a lock-free update to _counter.
1879   if (Atomic::xchg(0, &_counter) > 0) return;
1880 
1881   Thread* thread = Thread::current();
1882   assert(thread->is_Java_thread(), "Must be JavaThread");
1883   JavaThread *jt = (JavaThread *)thread;
1884 
1885   // Optional optimization -- avoid state transitions if there's
1886   // an interrupt pending.
1887   if (Thread::is_interrupted(thread, false)) {
1888     return;
1889   }
1890 
1891   // Next, demultiplex/decode time arguments
1892   struct timespec absTime;
1893   if (time < 0 || (isAbsolute && time == 0)) { // don't wait at all
1894     return;
1895   }
1896   if (time > 0) {
1897     to_abstime(&absTime, time, isAbsolute);
1898   }
1899 
1900   // Enter safepoint region
1901   // Beware of deadlocks such as 6317397.
1902   // The per-thread Parker:: mutex is a classic leaf-lock.
1903   // In particular a thread must never block on the Threads_lock while
1904   // holding the Parker:: mutex.  If safepoints are pending both the
1905   // the ThreadBlockInVM() CTOR and DTOR may grab Threads_lock.
1906   ThreadBlockInVM tbivm(jt);
1907 
1908   // Don't wait if cannot get lock since interference arises from
1909   // unparking. Also re-check interrupt before trying wait.
1910   if (Thread::is_interrupted(thread, false) ||
1911       pthread_mutex_trylock(_mutex) != 0) {
1912     return;
1913   }
1914 
1915   int status;
1916   if (_counter > 0)  { // no wait needed
1917     _counter = 0;
1918     status = pthread_mutex_unlock(_mutex);
1919     assert_status(status == 0, status, "invariant");
1920     // Paranoia to ensure our locked and lock-free paths interact
1921     // correctly with each other and Java-level accesses.
1922     OrderAccess::fence();
1923     return;
1924   }
1925 
1926   OSThreadWaitState osts(thread->osthread(), false /* not Object.wait() */);
1927   jt->set_suspend_equivalent();
1928   // cleared by handle_special_suspend_equivalent_condition() or java_suspend_self()
1929 
1930   assert(_cur_index == -1, "invariant");
1931   if (time == 0) {
1932     _cur_index = REL_INDEX; // arbitrary choice when not timed
1933     status = pthread_cond_wait(&_cond[_cur_index], _mutex);
1934     assert_status(status == 0, status, "cond_timedwait");
1935   }
1936   else {
1937     _cur_index = isAbsolute ? ABS_INDEX : REL_INDEX;
1938     status = pthread_cond_timedwait(&_cond[_cur_index], _mutex, &absTime);
1939     assert_status(status == 0 || status == ETIMEDOUT,
1940                   status, "cond_timedwait");
1941   }
1942   _cur_index = -1;
1943 
1944   _counter = 0;
1945   status = pthread_mutex_unlock(_mutex);
1946   assert_status(status == 0, status, "invariant");
1947   // Paranoia to ensure our locked and lock-free paths interact
1948   // correctly with each other and Java-level accesses.
1949   OrderAccess::fence();
1950 
1951   // If externally suspended while waiting, re-suspend
1952   if (jt->handle_special_suspend_equivalent_condition()) {
1953     jt->java_suspend_self();
1954   }
1955 }
1956 
1957 void Parker::unpark() {
1958   int status = pthread_mutex_lock(_mutex);
1959   assert_status(status == 0, status, "invariant");
1960   const int s = _counter;
1961   _counter = 1;
1962   // must capture correct index before unlocking
1963   int index = _cur_index;
1964   status = pthread_mutex_unlock(_mutex);
1965   assert_status(status == 0, status, "invariant");
1966 
1967   // Note that we signal() *after* dropping the lock for "immortal" Events.
1968   // This is safe and avoids a common class of futile wakeups.  In rare
1969   // circumstances this can cause a thread to return prematurely from
1970   // cond_{timed}wait() but the spurious wakeup is benign and the victim
1971   // will simply re-test the condition and re-park itself.
1972   // This provides particular benefit if the underlying platform does not
1973   // provide wait morphing.
1974 
1975   if (s < 1 && index != -1) {
1976     // thread is definitely parked
1977     status = pthread_cond_signal(&_cond[index]);
1978     assert_status(status == 0, status, "invariant");
1979   }
1980 }
1981 
1982 
1983 #endif // !SOLARIS