*
* ust_exit_mutex must never nest in ust_mutex.
*
+ * ust_fork_mutex must never nest in ust_mutex.
+ *
* ust_mutex_nest is a per-thread nesting counter, allowing the perf
* counter lazy initialization called by events within the statedump,
* which traces while the ust_mutex is held.
+ *
+ * ust_lock nests within the dynamic loader lock (within glibc) because
+ * it is taken within the library constructor.
*/
static pthread_mutex_t ust_mutex = PTHREAD_MUTEX_INITIALIZER;
*/
static pthread_mutex_t ust_exit_mutex = PTHREAD_MUTEX_INITIALIZER;
+/*
+ * ust_fork_mutex protects base address statedump tracing against forks. It
+ * prevents the dynamic loader lock to be taken (by base address statedump
+ * tracing) while a fork is happening, thus preventing deadlock issues with
+ * the dynamic loader lock.
+ */
+static pthread_mutex_t ust_fork_mutex = PTHREAD_MUTEX_INITIALIZER;
+
/* Should the ust comm thread quit ? */
static int lttng_ust_comm_should_quit;
if (ctor_passed && sock_info->statedump_pending) {
sock_info->statedump_pending = 0;
+ pthread_mutex_lock(&ust_fork_mutex);
lttng_handle_pending_statedump(sock_info);
+ pthread_mutex_unlock(&ust_fork_mutex);
}
}
if (ret == -1) {
PERROR("sigprocmask");
}
+
+ pthread_mutex_lock(&ust_fork_mutex);
+
ust_lock_nocheck();
rcu_bp_before_fork();
}
DBG("process %d", getpid());
ust_unlock();
+
+ pthread_mutex_unlock(&ust_fork_mutex);
+
/* Restore signals */
ret = sigprocmask(SIG_SETMASK, restore_sigset, NULL);
if (ret == -1) {