hotspot/src/os/bsd/vm/jsig.c

rev 7434 : 8072147: Preloading libjsig.dylib causes deadlock when signal() is called
Summary: Added check to prevent reentry of signal chaining code
Reviewed-by: dcubed, acorn, dholmes

*** 1,7 ****
  /*
!  * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.
--- 1,7 ----
  /*
!  * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.
*** 34,50 ****
--- 34,54 ----
  #include <dlfcn.h>
  #include <pthread.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <stdbool.h>
+ #include <string.h>
  
  #define MAXSIGNUM 32
  #define MASK(sig) ((unsigned int)1 << sig)
  
  static struct sigaction sact[MAXSIGNUM]; /* saved signal handlers */
  static unsigned int jvmsigs = 0; /* signals used by jvm */
  
+ static pthread_key_t reentry_flag_key;
+ static pthread_once_t reentry_key_init_once = PTHREAD_ONCE_INIT;
+ 
  /* used to synchronize the installation of signal handlers */
  static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
  static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
  static pthread_t tid = 0;
  
*** 57,66 ****
--- 61,79 ----
  static sigaction_t os_sigaction = 0; /* os's version of sigaction() */
  
  static bool jvm_signal_installing = false;
  static bool jvm_signal_installed = false;
  
+ #define check_status(cmd) \
+   do { \
+     int status = (cmd); \
+     if (status != 0) { \
+       printf("error %s (%d) in " #cmd "\n", strerror(status), status); \
+       exit(1); \
+     } \
+   } while (0)
+ 
  static void signal_lock() {
    pthread_mutex_lock(&mutex);
    /* When the jvm is installing its set of signal handlers, threads
     * other than the jvm thread should wait */
    if (jvm_signal_installing) {
*** 72,83 ****
--- 85,103 ----
  
  static void signal_unlock() {
    pthread_mutex_unlock(&mutex);
  }
  
+ static void reentry_tls_init() {
+     // value for reentry_flag_key will default to NULL (false)
+     check_status(pthread_key_create(&reentry_flag_key, NULL));
+ }
+ 
  static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
                                     bool is_sigset) {
+   sa_handler_t res;
+ 
    if (os_signal == NULL) {
      if (!is_sigset) {
        os_signal = (signal_t)dlsym(RTLD_NEXT, "signal");
      } else {
        os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset");
*** 85,95 ****
      if (os_signal == NULL) {
        printf("%s\n", dlerror());
        exit(0);
      }
    }
!   return (*os_signal)(sig, disp);
  }
  
  static void save_signal_handler(int sig, sa_handler_t disp) {
    sigset_t set;
    sact[sig].sa_handler = disp;
--- 105,120 ----
      if (os_signal == NULL) {
        printf("%s\n", dlerror());
        exit(0);
      }
    }
!   check_status(pthread_once(&reentry_key_init_once, reentry_tls_init));
!   // set reentry_flag_key to non-NULL to show reentry
!   check_status(pthread_setspecific(reentry_flag_key, &res));
!   res = (*os_signal)(sig, disp);
!   check_status(pthread_setspecific(reentry_flag_key, NULL));
!   return res;
  }
  
  static void save_signal_handler(int sig, sa_handler_t disp) {
    sigset_t set;
    sact[sig].sa_handler = disp;
*** 159,168 ****
--- 184,198 ----
  int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
    int res;
    bool sigused;
    struct sigaction oldAct;
  
+   check_status(pthread_once(&reentry_key_init_once, reentry_tls_init));
+   if (pthread_getspecific(reentry_flag_key) != NULL) {
+     return call_os_sigaction(sig, act, oact);
+   }
+ 
    signal_lock();
  
    sigused = (MASK(sig) & jvmsigs) != 0;
    if (jvm_signal_installed && sigused) {
      /* jvm has installed its signal handler for this signal. */