openjdk/jdk · warning

VM warning: the use of signal() and sigset() for signal…

Error message

 VM warning: the use of signal() and sigset() for signal chaining was deprecated in version 16.0 and will be removed in a future release. Use sigaction() instead.

What it means

Deprecation notice from libjsig (the JDK's signal-chaining library, preloaded via LD_PRELOAD on Solaris/Linux HotSpot). If application or library code calls signal() or sigset() (instead of sigaction()) to install a signal handler while the JVM is running, libjsig intercepts the call, prints this one-time warning, and forwards the registration to the JVM's chained handling. Behavior is still correct; the API is deprecated because signal()'s unreliable semantics do not compose well with JVM signal chaining.

Solutions

1. Change the offending native code to install handlers with sigaction() instead of signal()/sigset() — this is the only real fix
2. Identify the caller: run under a debugger with a breakpoint on signal(), or use tools like 'ltrace -e signal' to catch who calls it
3. If the caller is a third-party library, upgrade to a version using sigaction or report it upstream
4. The warning is printed only once per process; it is harmless unless the API is actually removed in a future release — plan the migration before then

Example fix

// before (C)
signal(SIGTERM, my_handler);

// after
struct sigaction sa;
sa.sa_handler = my_handler;
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
sigaction(SIGTERM, &sa, NULL);

// Audit native code linked into the process for deprecated calls before shipping:
//   ltrace -e signal -e sigset -- ./myapp 2>&1 | grep -v '^---'
// or link-time: nm -D libmynative.so | grep -w signal

When it happens

Trigger: Any call to signal() or sigset() from JVM-attached native code (JNI library, agent, or the application itself) after libjsig was initialized. Typical sources: C libraries installing SIGINT/SIGTERM/SIGPIPE handlers, legacy code ported from older Unix codebases.

Common situations: Running a Java app that loads a third-party native library which registers signal handlers with signal(); using tools or daemons that call signal() during startup before/after JVM init; upgrading to JDK 16+ where the warning was introduced and seeing it in logs.

Related errors

• no '/' found in the full path of the executable
• Could not create SplashScreen thread, error number
• Couldn't find X Input Context\n
• CreateProcess failed: %lu
• Error: Out of memory in ADLC\n

AI-assisted analysis of openjdk/jdk@88dfb74bbe (2026-08-14). Data as JSON: /api/errors/87e3924b370e8621. Report an issue: GitHub.

Appendix: source

Thrown at src/java.base/unix/native/libjsig/jsig.c:97

   * other than the jvm thread should wait. */
  if (jvm_signal_installing) {
    /* tid is not initialized until jvm_signal_installing is set to true. */
    if (pthread_equal(tid, pthread_self()) == 0) {
      do {
        pthread_cond_wait(&cond, &mutex);
      } while (jvm_signal_installing);
    }
  }
}

static void signal_unlock() {
  pthread_mutex_unlock(&mutex);
}

static void print_deprecation_warning() {
  if (!warning_printed) {
    warning_printed = true;
    fprintf(stderr, HOTSPOT_VM_DISTRO " VM warning: the use of signal() and sigset() "
            "for signal chaining was deprecated in version 16.0 and will "
            "be removed in a future release. Use sigaction() instead.\n");
  }
}

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_function_t)dlsym(RTLD_NEXT, "signal");
    } else {
      os_signal = (signal_function_t)dlsym(RTLD_NEXT, "sigset");
    }
    if (os_signal == NULL) {
      printf("%s\n", dlerror());
      exit(0);

View on GitHub (pinned to 88dfb74bbe)