Mask signals during background thread creation.

This prevents signals from being inadvertently delivered to background
threads.

1 files changed, 35 insertions, 3 deletions

diff --git a/src/background_thread.c b/src/background_thread.c
index 1ff5944..f0aa04f 100644
--- a/src/background_thread.c
+++ b/src/background_thread.c
@@ -347,6 +347,38 @@ background_threads_disable_single(tsd_t *tsd, background_thread_info_t *info) {
 
 static void *background_thread_entry(void *ind_arg);
 
+static int
+background_thread_create_signals_masked(pthread_t *thread,
+    const pthread_attr_t *attr, void *(*start_routine)(void *), void *arg) {
+	/*
+	 * Mask signals during thread creation so that the thread inherits
+	 * an empty signal set.
+	 */
+	sigset_t set;
+	sigemptyset(&set);
+	sigset_t oldset;
+	int mask_err = pthread_sigmask(SIG_SETMASK, &set, &oldset);
+	if (mask_err != 0) {
+		return mask_err;
+	}
+	int create_err = pthread_create_wrapper(thread, attr, start_routine,
+	    arg);
+	/*
+	 * Restore the signal mask.  Failure to restore the signal mask here
+	 * changes program behavior.
+	 */
+	int restore_err = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+	if (restore_err != 0) {
+		malloc_printf("<jemalloc>: background thread creation "
+		    "failed (%d), and signal mask restoration failed "
+		    "(%d)\n", create_err, restore_err);
+		if (opt_abort) {
+			abort();
+		}
+	}
+	return create_err;
+}
+
 static void
 check_background_thread_creation(tsd_t *tsd, unsigned *n_created,
     bool *created_threads) {
@@ -377,8 +409,8 @@ label_restart:
 		malloc_mutex_unlock(tsd_tsdn(tsd), &background_thread_lock);
 
 		pre_reentrancy(tsd);
-		int err = pthread_create_wrapper(&info->thread, NULL,
-		    background_thread_entry, (void *)(uintptr_t)i);
+		int err = background_thread_create_signals_masked(&info->thread,
+		    NULL, background_thread_entry, (void *)(uintptr_t)i);
 		post_reentrancy(tsd);
 
 		if (err == 0) {
@@ -528,7 +560,7 @@ background_thread_create(tsd_t *tsd, unsigned arena_ind) {
 	 * To avoid complications (besides reentrancy), create internal
 	 * background threads with the underlying pthread_create.
 	 */
-	int err = pthread_create_wrapper(&info->thread, NULL,
+	int err = background_thread_create_signals_masked(&info->thread, NULL,
 	    background_thread_entry, (void *)thread_ind);
 	post_reentrancy(tsd);