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 "utilities/globalDefinitions.hpp"
26 #include "prims/jvm.h"
27 #include "semaphore_posix.hpp"
28 #include "runtime/frame.inline.hpp"
29 #include "runtime/interfaceSupport.hpp"
30 #include "runtime/os.hpp"
31 #include "utilities/macros.hpp"
32 #include "utilities/vmError.hpp"
33
34 #include <signal.h>
35 #include <unistd.h>
36 #include <sys/resource.h>
37 #include <sys/utsname.h>
38 #include <pthread.h>
39 #include <semaphore.h>
40 #include <signal.h>
41
42 // Todo: provide a os::get_max_process_id() or similar. Number of processes
43 // may have been configured, can be read more accurately from proc fs etc.
44 #ifndef MAX_PID
45 #define MAX_PID INT_MAX
46 #endif
47 #define IS_VALID_PID(p) (p > 0 && p < MAX_PID)
48
49 // Check core dump limit and report possible place where core can be found
50 void os::check_dump_limit(char* buffer, size_t bufferSize) {
51 if (!FLAG_IS_DEFAULT(CreateCoredumpOnCrash) && !CreateCoredumpOnCrash) {
52 jio_snprintf(buffer, bufferSize, "CreateCoredumpOnCrash is disabled from command line");
53 VMError::record_coredump_status(buffer, false);
54 return;
55 }
56
57 int n;
58 struct rlimit rlim;
59 bool success;
60
1377 return ret == 0;
1378 }
1379
1380 bool PosixSemaphore::timedwait(struct timespec ts) {
1381 while (true) {
1382 int result = sem_timedwait(&_semaphore, &ts);
1383 if (result == 0) {
1384 return true;
1385 } else if (errno == EINTR) {
1386 continue;
1387 } else if (errno == ETIMEDOUT) {
1388 return false;
1389 } else {
1390 assert_with_errno(false, "timedwait failed");
1391 return false;
1392 }
1393 }
1394 }
1395
1396 #endif // __APPLE__
|
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 "utilities/globalDefinitions.hpp"
26 #include "prims/jvm.h"
27 #include "semaphore_posix.hpp"
28 #include "runtime/frame.inline.hpp"
29 #include "runtime/interfaceSupport.hpp"
30 #include "runtime/os.hpp"
31 #include "utilities/macros.hpp"
32 #include "utilities/vmError.hpp"
33
34 #include <dlfcn.h>
35 #include <pthread.h>
36 #include <semaphore.h>
37 #include <signal.h>
38 #include <sys/resource.h>
39 #include <sys/utsname.h>
40 #include <time.h>
41 #include <unistd.h>
42
43 // Todo: provide a os::get_max_process_id() or similar. Number of processes
44 // may have been configured, can be read more accurately from proc fs etc.
45 #ifndef MAX_PID
46 #define MAX_PID INT_MAX
47 #endif
48 #define IS_VALID_PID(p) (p > 0 && p < MAX_PID)
49
50 // Check core dump limit and report possible place where core can be found
51 void os::check_dump_limit(char* buffer, size_t bufferSize) {
52 if (!FLAG_IS_DEFAULT(CreateCoredumpOnCrash) && !CreateCoredumpOnCrash) {
53 jio_snprintf(buffer, bufferSize, "CreateCoredumpOnCrash is disabled from command line");
54 VMError::record_coredump_status(buffer, false);
55 return;
56 }
57
58 int n;
59 struct rlimit rlim;
60 bool success;
61
1378 return ret == 0;
1379 }
1380
1381 bool PosixSemaphore::timedwait(struct timespec ts) {
1382 while (true) {
1383 int result = sem_timedwait(&_semaphore, &ts);
1384 if (result == 0) {
1385 return true;
1386 } else if (errno == EINTR) {
1387 continue;
1388 } else if (errno == ETIMEDOUT) {
1389 return false;
1390 } else {
1391 assert_with_errno(false, "timedwait failed");
1392 return false;
1393 }
1394 }
1395 }
1396
1397 #endif // __APPLE__
1398
1399
1400 // Shared pthread_mutex/cond based PlatformEvent implementation.
1401 // Not currently usable by Solaris
1402
1403 #ifndef SOLARIS
1404
1405 // Shared condattr object for use with relative timed-waits. Will be associated
1406 // with CLOCK_MONOTONIC if available to avoid issues with time-of-day changes,
1407 // but otherwise whatever default is used by the platform - generally the
1408 // time-of-day clock
1409 static pthread_condattr_t _condAttr[1];
1410
1411 // Shared mutexattr to explicitly set the type to PTHREAD_MUTEX_NORMAL as not
1412 // all systems (e.g. FreeBSD) map the default to "normal".
1413 static pthread_mutexattr_t _mutexAttr[1];
1414
1415 // common basic initialization that is always supported
1416 static void pthread_init_common(void) {
1417 int status;
1418 if ((status = pthread_condattr_init(_condAttr)) != 0) {
1419 fatal("pthread_condattr_init: %s", os::strerror(status));
1420 }
1421 if ((status = pthread_mutexattr_init(_mutexAttr)) != 0) {
1422 fatal("pthread_mutexattr_init: %s", os::strerror(status));
1423 }
1424 if ((status = pthread_mutexattr_settype(_mutexAttr, PTHREAD_MUTEX_NORMAL)) != 0) {
1425 fatal("pthread_mutexattr_settype: %s", os::strerror(status));
1426 }
1427 }
1428
1429 // Not all POSIX types and API's are available on all notionally "posix"
1430 // platforms. If we have build-time support then we will check for actual
1431 // runtime support via dlopen/dlsym lookup. This allows for running on an
1432 // older OS version compared to the build platform. But if there is no
1433 // build time support then there can not be any runtime support as we do not
1434 // know what the runtime types would be (for example clockid_t might be an
1435 // int or int64_t.
1436 //
1437 #ifdef SUPPORTS_CLOCK_MONOTONIC
1438
1439 // This means we have clockid_t, clock_gettime et al and CLOCK_MONOTONIC
1440
1441 static int (*_clock_gettime)(clockid_t, struct timespec *);
1442 static int (*_pthread_condattr_setclock)(pthread_condattr_t *, clockid_t);
1443
1444 static bool _use_clock_monotonic_condattr;
1445
1446 // determine what POSIX API's are present and do appropriate
1447 // configuration
1448 void os::Posix::init(void) {
1449
1450 // NOTE: no logging available when this is called. Put logging
1451 // statements in init_2().
1452
1453 // copied from os::Linux::clock_init(). The duplication is temporary.
1454
1455 // 1. Check for CLOCK_MONOTONIC support
1456
1457 void* handle = NULL;
1458
1459 // For linux we need librt, for other OS we can find
1460 // this function in regular libc
1461 #ifdef NEEDS_LIBRT
1462 // we do dlopen's in this particular order due to bug in linux
1463 // dynamical loader (see 6348968) leading to crash on exit
1464 handle = dlopen("librt.so.1", RTLD_LAZY);
1465 if (handle == NULL) {
1466 handle = dlopen("librt.so", RTLD_LAZY);
1467 }
1468 #endif
1469
1470 if (handle == NULL) {
1471 handle = RTLD_DEFAULT;
1472 }
1473
1474 _clock_gettime = NULL;
1475
1476 int (*clock_getres_func)(clockid_t, struct timespec*) =
1477 (int(*)(clockid_t, struct timespec*))dlsym(handle, "clock_getres");
1478 int (*clock_gettime_func)(clockid_t, struct timespec*) =
1479 (int(*)(clockid_t, struct timespec*))dlsym(handle, "clock_gettime");
1480 if (clock_getres_func != NULL && clock_gettime_func != NULL) {
1481 // we assume that if both clock_gettime and clock_getres support
1482 // CLOCK_MONOTONIC then the OS provides true high-res monotonic clock
1483 struct timespec res;
1484 struct timespec tp;
1485 if (clock_getres_func(CLOCK_MONOTONIC, &res) == 0 &&
1486 clock_gettime_func(CLOCK_MONOTONIC, &tp) == 0) {
1487 // yes, monotonic clock is supported
1488 _clock_gettime = clock_gettime_func;
1489 } else {
1490 #ifdef NEEDS_LIBRT
1491 // close librt if there is no monotonic clock
1492 if (handle != RTLD_DEFAULT) {
1493 dlclose(handle);
1494 }
1495 #endif
1496 }
1497 }
1498
1499 // 2. Check for pthread_condattr_setclock support
1500
1501 _pthread_condattr_setclock = NULL;
1502
1503 // libpthread is already loaded
1504 int (*condattr_setclock_func)(pthread_condattr_t*, clockid_t) =
1505 (int (*)(pthread_condattr_t*, clockid_t))dlsym(RTLD_DEFAULT,
1506 "pthread_condattr_setclock");
1507 if (condattr_setclock_func != NULL) {
1508 _pthread_condattr_setclock = condattr_setclock_func;
1509 }
1510
1511 // Now do general initialization
1512
1513 pthread_init_common();
1514
1515 int status;
1516 if (_pthread_condattr_setclock != NULL &&
1517 _clock_gettime != NULL) {
1518 _use_clock_monotonic_condattr = true;
1519
1520 if ((status = _pthread_condattr_setclock(_condAttr, CLOCK_MONOTONIC)) != 0) {
1521 if (status == EINVAL) {
1522 _use_clock_monotonic_condattr = false;
1523 warning("Unable to use monotonic clock with relative timed-waits" \
1524 " - changes to the time-of-day clock may have adverse affects");
1525 } else {
1526 fatal("pthread_condattr_setclock: %s", os::strerror(status));
1527 }
1528 }
1529 }
1530 else {
1531 _use_clock_monotonic_condattr = false;
1532 }
1533 }
1534
1535 void os::Posix::init_2(void) {
1536 log_info(os)("Use of CLOCK_MONOTONIC is%s supported",
1537 (_clock_gettime != NULL ? "" : " not"));
1538 log_info(os)("Use of pthread_condattr_setclock is%s supported",
1539 (_pthread_condattr_setclock != NULL ? "" : " not"));
1540 log_info(os)("Relative timed-wait using pthread_cond_timedwait is associated with %s",
1541 _use_clock_monotonic_condattr ? "CLOCK_MONOTONIC" : "the default clock");
1542 }
1543
1544 #else // !SUPPORTS_CLOCK_MONOTONIC
1545
1546 void os::Posix::init(void) {
1547 pthread_init_common();
1548 }
1549
1550 void os::Posix::init_2(void) {
1551 log_info(os)("Use of CLOCK_MONOTONIC is not supported");
1552 log_info(os)("Use of pthread_condattr_setclock is not supported");
1553 log_info(os)("Relative timed-wait using pthread_cond_timedwait is associated with the default clock");
1554 }
1555
1556 #endif // SUPPORTS_CLOCK_MONOTONIC
1557
1558 os::PlatformEvent::PlatformEvent() {
1559 int status = pthread_cond_init(_cond, _condAttr);
1560 assert_status(status == 0, status, "cond_init");
1561 status = pthread_mutex_init(_mutex, _mutexAttr);
1562 assert_status(status == 0, status, "mutex_init");
1563 _event = 0;
1564 _nParked = 0;
1565 }
1566
1567 // Utility to convert the given timeout to an absolute timespec
1568 // (based on the appropriate clock) to use with pthread_cond_timewait.
1569 // The clock queried here must be the clock used to manage the
1570 // timeout of the condition variable.
1571 //
1572 // The passed in timeout value is either a relative time in nanoseconds
1573 // or an absolute time in milliseconds. A relative timeout will be
1574 // associated with CLOCK_MONOTONIC if available; otherwise, or if absolute,
1575 // the default time-of-day clock will be used.
1576
1577 // Given time is a 64-bit value and the time_t used in the timespec is
1578 // sometimes a signed-32-bit value we have to watch for overflow if times
1579 // way in the future are given. Further on Solaris versions
1580 // prior to 10 there is a restriction (see cond_timedwait) that the specified
1581 // number of seconds, in abstime, is less than current_time + 100,000,000.
1582 // As it will be over 20 years before "now + 100000000" will overflow we can
1583 // ignore overflow and just impose a hard-limit on seconds using the value
1584 // of "now + 100,000,000". This places a limit on the timeout of about 3.17
1585 // years from "now".
1586 //
1587 #define MAX_SECS 100000000
1588
1589 static void to_abstime(timespec* abstime, jlong timeout, bool isAbsolute) {
1590
1591 if (timeout < 0)
1592 timeout = 0;
1593
1594 time_t max_secs = 0;
1595
1596 #ifdef SUPPORTS_CLOCK_MONOTONIC
1597
1598 if (_use_clock_monotonic_condattr && !isAbsolute) {
1599 // relative timeout in nanoseconds
1600 jlong seconds = timeout / NANOUNITS;
1601 timeout %= NANOUNITS; // remaining nanos
1602
1603 struct timespec now;
1604 int status = _clock_gettime(CLOCK_MONOTONIC, &now);
1605 assert_status(status == 0, status, "clock_gettime");
1606
1607 max_secs = now.tv_sec + MAX_SECS;
1608 if (seconds >= MAX_SECS) {
1609 // More seconds than we can add, so pin to max_secs
1610 abstime->tv_sec = max_secs;
1611 abstime->tv_nsec = 0;
1612 }
1613 else {
1614 abstime->tv_sec = now.tv_sec + seconds;
1615 long nsecs = now.tv_nsec + timeout;
1616 if (nsecs >= NANOUNITS) { // overflow
1617 abstime->tv_sec += 1;
1618 nsecs -= NANOUNITS;
1619 }
1620 abstime->tv_nsec = nsecs;
1621 }
1622 }
1623 else {
1624
1625 #else
1626
1627 { // match the block scope
1628
1629 #endif // SUPPORTS_CLOCK_MONOTONIC
1630
1631 // time-of-day clock is all we can reliably use
1632 struct timeval now;
1633 int status = gettimeofday(&now, NULL);
1634 assert(status == 0, "gettimeofday");
1635 max_secs = now.tv_sec + MAX_SECS;
1636
1637 if (isAbsolute) {
1638 // absolute timeout in milliseconds
1639 jlong seconds = timeout / MILLIUNITS;
1640 timeout %= MILLIUNITS; // remaining millis
1641
1642 if (seconds >= max_secs) {
1643 // Absolue seconds exceeds allow max, so pin to max_secs
1644 abstime->tv_sec = max_secs;
1645 abstime->tv_nsec = 0;
1646 }
1647 else {
1648 abstime->tv_sec = seconds;
1649 abstime->tv_nsec = timeout * (NANOUNITS/MILLIUNITS);
1650 }
1651 }
1652 else {
1653 // relative timeout in nanoseconds
1654 jlong seconds = timeout / NANOUNITS;
1655 timeout %= NANOUNITS; // remaining nanos
1656
1657 if (seconds >= MAX_SECS) {
1658 // More seconds than we can add, so pin to max_secs
1659 abstime->tv_sec = max_secs;
1660 abstime->tv_nsec = 0;
1661 }
1662 else {
1663 abstime->tv_sec = now.tv_sec + seconds;
1664 jlong micros_left = timeout / (NANOUNITS/MICROUNITS);
1665 long usec = now.tv_usec + micros_left;
1666 if (usec >= MICROUNITS) { // overflow
1667 abstime->tv_sec += 1;
1668 usec -= MICROUNITS;
1669 }
1670 abstime->tv_nsec = usec * (NANOUNITS/MICROUNITS);
1671 }
1672 }
1673 }
1674
1675 assert(abstime->tv_sec >= 0, "tv_sec < 0");
1676 assert(abstime->tv_sec <= max_secs, "tv_sec > max_secs");
1677 assert(abstime->tv_nsec >= 0, "tv_nsec < 0");
1678 assert(abstime->tv_nsec < NANOSECS_PER_SEC, "tv_nsec >= nanos_per_sec");
1679
1680 }
1681
1682 // PlatformEvent
1683 //
1684 // Assumption:
1685 // Only one parker can exist on an event, which is why we allocate
1686 // them per-thread. Multiple unparkers can coexist.
1687 //
1688 // _event serves as a restricted-range semaphore.
1689 // -1 : thread is blocked, i.e. there is a waiter
1690 // 0 : neutral: thread is running or ready,
1691 // could have been signaled after a wait started
1692 // 1 : signaled - thread is running or ready
1693 //
1694 // Having three states allows for some detection of bad usage - see
1695 // comments on unpark().
1696
1697 void os::PlatformEvent::park() { // AKA "down()"
1698 // Transitions for _event:
1699 // -1 => -1 : illegal
1700 // 1 => 0 : pass - return immediately
1701 // 0 => -1 : block; then set _event to 0 before returning
1702
1703 // Invariant: Only the thread associated with the PlatformEvent
1704 // may call park().
1705 assert(_nParked == 0, "invariant");
1706
1707 int v;
1708
1709 // atomically decrement _event
1710 for (;;) {
1711 v = _event;
1712 if (Atomic::cmpxchg(v-1, &_event, v) == v) break;
1713 }
1714 guarantee(v >= 0, "invariant");
1715
1716 if (v == 0) { // Do this the hard way by blocking ...
1717 int status = pthread_mutex_lock(_mutex);
1718 assert_status(status == 0, status, "mutex_lock");
1719 guarantee(_nParked == 0, "invariant");
1720 ++_nParked;
1721 while (_event < 0) {
1722 // OS-level "spurious wakeups" are ignored
1723 status = pthread_cond_wait(_cond, _mutex);
1724 assert_status(status == 0, status, "cond_wait");
1725 }
1726 --_nParked;
1727
1728 _event = 0;
1729 status = pthread_mutex_unlock(_mutex);
1730 assert_status(status == 0, status, "mutex_unlock");
1731 // Paranoia to ensure our locked and lock-free paths interact
1732 // correctly with each other.
1733 OrderAccess::fence();
1734 }
1735 guarantee(_event >= 0, "invariant");
1736 }
1737
1738 int os::PlatformEvent::park(jlong millis) {
1739 // Transitions for _event:
1740 // -1 => -1 : illegal
1741 // 1 => 0 : pass - return immediately
1742 // 0 => -1 : block; then set _event to 0 before returning
1743
1744 // Invariant: Only the thread associated with the Event/PlatformEvent
1745 // may call park().
1746 assert(_nParked == 0, "invariant");
1747
1748 int v;
1749 // atomically decrement _event
1750 for (;;) {
1751 v = _event;
1752 if (Atomic::cmpxchg(v-1, &_event, v) == v) break;
1753 }
1754 guarantee(v >= 0, "invariant");
1755
1756 if (v == 0) { // Do this the hard way by blocking ...
1757 struct timespec abst;
1758 to_abstime(&abst, millis * (NANOUNITS/MILLIUNITS), false);
1759
1760 int ret = OS_TIMEOUT;
1761 int status = pthread_mutex_lock(_mutex);
1762 assert_status(status == 0, status, "mutex_lock");
1763 guarantee(_nParked == 0, "invariant");
1764 ++_nParked;
1765
1766 while (_event < 0) {
1767 status = pthread_cond_timedwait(_cond, _mutex, &abst);
1768 assert_status(status == 0 || status == ETIMEDOUT,
1769 status, "cond_timedwait");
1770 // OS-level "spurious wakeups" are ignored unless the archaic
1771 // FilterSpuriousWakeups is set false. That flag should be obsoleted.
1772 if (!FilterSpuriousWakeups) break;
1773 if (status == ETIMEDOUT) break;
1774 }
1775 --_nParked;
1776
1777 if (_event >= 0) {
1778 ret = OS_OK;
1779 }
1780
1781 _event = 0;
1782 status = pthread_mutex_unlock(_mutex);
1783 assert_status(status == 0, status, "mutex_unlock");
1784 // Paranoia to ensure our locked and lock-free paths interact
1785 // correctly with each other.
1786 OrderAccess::fence();
1787 return ret;
1788 }
1789 return OS_OK;
1790 }
1791
1792 void os::PlatformEvent::unpark() {
1793 // Transitions for _event:
1794 // 0 => 1 : just return
1795 // 1 => 1 : just return
1796 // -1 => either 0 or 1; must signal target thread
1797 // That is, we can safely transition _event from -1 to either
1798 // 0 or 1.
1799 // See also: "Semaphores in Plan 9" by Mullender & Cox
1800 //
1801 // Note: Forcing a transition from "-1" to "1" on an unpark() means
1802 // that it will take two back-to-back park() calls for the owning
1803 // thread to block. This has the benefit of forcing a spurious return
1804 // from the first park() call after an unpark() call which will help
1805 // shake out uses of park() and unpark() without checking state conditions
1806 // properly. This spurious return doesn't manifest itself in any user code
1807 // but only in the correctly written condition checking loops of ObjectMonitor,
1808 // Mutex/Monitor, Thread::muxAcquire and os::sleep
1809
1810 if (Atomic::xchg(1, &_event) >= 0) return;
1811
1812 int status = pthread_mutex_lock(_mutex);
1813 assert_status(status == 0, status, "mutex_lock");
1814 int anyWaiters = _nParked;
1815 assert(anyWaiters == 0 || anyWaiters == 1, "invariant");
1816 status = pthread_mutex_unlock(_mutex);
1817 assert_status(status == 0, status, "mutex_unlock");
1818
1819 // Note that we signal() *after* dropping the lock for "immortal" Events.
1820 // This is safe and avoids a common class of futile wakeups. In rare
1821 // circumstances this can cause a thread to return prematurely from
1822 // cond_{timed}wait() but the spurious wakeup is benign and the victim
1823 // will simply re-test the condition and re-park itself.
1824 // This provides particular benefit if the underlying platform does not
1825 // provide wait morphing.
1826
1827 if (anyWaiters != 0) {
1828 status = pthread_cond_signal(_cond);
1829 assert_status(status == 0, status, "cond_signal");
1830 }
1831 }
1832
1833 // JSR166 support
1834
1835 os::PlatformParker::PlatformParker() {
1836 int status;
1837 status = pthread_cond_init(&_cond[REL_INDEX], _condAttr);
1838 assert_status(status == 0, status, "cond_init rel");
1839 status = pthread_cond_init(&_cond[ABS_INDEX], NULL);
1840 assert_status(status == 0, status, "cond_init abs");
1841 status = pthread_mutex_init(_mutex, _mutexAttr);
1842 assert_status(status == 0, status, "mutex_init");
1843 _cur_index = -1; // mark as unused
1844 }
1845
1846 // Parker::park decrements count if > 0, else does a condvar wait. Unpark
1847 // sets count to 1 and signals condvar. Only one thread ever waits
1848 // on the condvar. Contention seen when trying to park implies that someone
1849 // is unparking you, so don't wait. And spurious returns are fine, so there
1850 // is no need to track notifications.
1851
1852 void Parker::park(bool isAbsolute, jlong time) {
1853
1854 // Optional fast-path check:
1855 // Return immediately if a permit is available.
1856 // We depend on Atomic::xchg() having full barrier semantics
1857 // since we are doing a lock-free update to _counter.
1858 if (Atomic::xchg(0, &_counter) > 0) return;
1859
1860 Thread* thread = Thread::current();
1861 assert(thread->is_Java_thread(), "Must be JavaThread");
1862 JavaThread *jt = (JavaThread *)thread;
1863
1864 // Optional optimization -- avoid state transitions if there's
1865 // an interrupt pending.
1866 if (Thread::is_interrupted(thread, false)) {
1867 return;
1868 }
1869
1870 // Next, demultiplex/decode time arguments
1871 struct timespec absTime;
1872 if (time < 0 || (isAbsolute && time == 0)) { // don't wait at all
1873 return;
1874 }
1875 if (time > 0) {
1876 to_abstime(&absTime, time, isAbsolute);
1877 }
1878
1879 // Enter safepoint region
1880 // Beware of deadlocks such as 6317397.
1881 // The per-thread Parker:: mutex is a classic leaf-lock.
1882 // In particular a thread must never block on the Threads_lock while
1883 // holding the Parker:: mutex. If safepoints are pending both the
1884 // the ThreadBlockInVM() CTOR and DTOR may grab Threads_lock.
1885 ThreadBlockInVM tbivm(jt);
1886
1887 // Don't wait if cannot get lock since interference arises from
1888 // unparking. Also re-check interrupt before trying wait.
1889 if (Thread::is_interrupted(thread, false) ||
1890 pthread_mutex_trylock(_mutex) != 0) {
1891 return;
1892 }
1893
1894 int status;
1895 if (_counter > 0) { // no wait needed
1896 _counter = 0;
1897 status = pthread_mutex_unlock(_mutex);
1898 assert_status(status == 0, status, "invariant");
1899 // Paranoia to ensure our locked and lock-free paths interact
1900 // correctly with each other and Java-level accesses.
1901 OrderAccess::fence();
1902 return;
1903 }
1904
1905 OSThreadWaitState osts(thread->osthread(), false /* not Object.wait() */);
1906 jt->set_suspend_equivalent();
1907 // cleared by handle_special_suspend_equivalent_condition() or java_suspend_self()
1908
1909 assert(_cur_index == -1, "invariant");
1910 if (time == 0) {
1911 _cur_index = REL_INDEX; // arbitrary choice when not timed
1912 status = pthread_cond_wait(&_cond[_cur_index], _mutex);
1913 assert_status(status == 0, status, "cond_timedwait");
1914 }
1915 else {
1916 _cur_index = isAbsolute ? ABS_INDEX : REL_INDEX;
1917 status = pthread_cond_timedwait(&_cond[_cur_index], _mutex, &absTime);
1918 assert_status(status == 0 || status == ETIMEDOUT,
1919 status, "cond_timedwait");
1920 }
1921 _cur_index = -1;
1922
1923 _counter = 0;
1924 status = pthread_mutex_unlock(_mutex);
1925 assert_status(status == 0, status, "invariant");
1926 // Paranoia to ensure our locked and lock-free paths interact
1927 // correctly with each other and Java-level accesses.
1928 OrderAccess::fence();
1929
1930 // If externally suspended while waiting, re-suspend
1931 if (jt->handle_special_suspend_equivalent_condition()) {
1932 jt->java_suspend_self();
1933 }
1934 }
1935
1936 void Parker::unpark() {
1937 int status = pthread_mutex_lock(_mutex);
1938 assert_status(status == 0, status, "invariant");
1939 const int s = _counter;
1940 _counter = 1;
1941 // must capture correct index before unlocking
1942 int index = _cur_index;
1943 status = pthread_mutex_unlock(_mutex);
1944 assert_status(status == 0, status, "invariant");
1945
1946 // Note that we signal() *after* dropping the lock for "immortal" Events.
1947 // This is safe and avoids a common class of futile wakeups. In rare
1948 // circumstances this can cause a thread to return prematurely from
1949 // cond_{timed}wait() but the spurious wakeup is benign and the victim
1950 // will simply re-test the condition and re-park itself.
1951 // This provides particular benefit if the underlying platform does not
1952 // provide wait morphing.
1953
1954 if (s < 1 && index != -1) {
1955 // thread is definitely parked
1956 status = pthread_cond_signal(&_cond[index]);
1957 assert_status(status == 0, status, "invariant");
1958 }
1959 }
1960
1961
1962 #endif // !SOLARIS
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