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Fix race condition in signal handler query #13712

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Merged
merged 3 commits into from
Jun 28, 2025
Merged

Fix race condition in signal handler query #13712

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da8385b
Fix race condition in signal handler query
sferik Jun 26, 2025
0fa364c
Initialize signal lock dynamically and reset after fork
sferik Jun 27, 2025
76baa0f
Fix signal handler mutex initialization conditions
sferik Jun 28, 2025
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1 change: 1 addition & 0 deletions internal/signal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ void (*ruby_posix_signal(int, void (*)(int)))(int);

RUBY_SYMBOL_EXPORT_BEGIN
/* signal.c (export) */
void rb_signal_atfork(void);
RUBY_SYMBOL_EXPORT_END

#endif /* INTERNAL_SIGNAL_H */
21 changes: 19 additions & 2 deletions signal.c
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Expand Up @@ -664,6 +664,10 @@ ruby_nativethread_signal(int signum, sighandler_t handler)
#endif
#endif

#if !defined(POSIX_SIGNAL) && !defined(SIG_GET)
static rb_nativethread_lock_t sig_check_lock;
#endif

static int
signal_ignored(int sig)
{
Expand All @@ -678,9 +682,11 @@ signal_ignored(int sig)
// SIG_GET: Returns the current value of the signal.
func = signal(sig, SIG_GET);
#else
// TODO: this is not a thread-safe way to do it. Needs lock.
sighandler_t old = signal(sig, SIG_DFL);
sighandler_t old;
rb_native_mutex_lock(&sig_check_lock);
old = signal(sig, SIG_DFL);
signal(sig, old);
rb_native_mutex_unlock(&sig_check_lock);
func = old;
#endif
if (func == SIG_IGN) return 1;
Expand Down Expand Up @@ -1509,6 +1515,9 @@ Init_signal(void)
rb_define_method(rb_eSignal, "signo", esignal_signo, 0);
rb_alias(rb_eSignal, rb_intern_const("signm"), rb_intern_const("message"));
rb_define_method(rb_eInterrupt, "initialize", interrupt_init, -1);
#if !defined(POSIX_SIGNAL) && !defined(SIG_GET)
rb_native_mutex_initialize(&sig_check_lock);
#endif

// It should be ready to call rb_signal_exec()
VM_ASSERT(GET_THREAD()->pending_interrupt_queue);
Expand Down Expand Up @@ -1561,3 +1570,11 @@ Init_signal(void)

rb_enable_interrupt();
}

void
rb_signal_atfork(void)
{
#if defined(HAVE_WORKING_FORK) && !defined(POSIX_SIGNAL) && !defined(SIG_GET)
rb_native_mutex_initialize(&sig_check_lock);
#endif
}
1 change: 1 addition & 0 deletions thread.c
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Expand Up @@ -4933,6 +4933,7 @@ rb_thread_atfork_internal(rb_thread_t *th, void (*atfork)(rb_thread_t *, const r

thread_sched_atfork(TH_SCHED(th));
ubf_list_atfork();
rb_signal_atfork();

// OK. Only this thread accesses:
ccan_list_for_each(&vm->ractor.set, r, vmlr_node) {
Expand Down
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