restore lock-skipping for processes that return to single-threaded state

[musl] / src / thread / pthread_create.c

diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index 6a3b0c2..6bdfb44 100644 (file)
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -118,8 +118,8 @@ _Noreturn void __pthread_exit(void *result)
         * until the lock is released, which only happens after SYS_exit
         * has been called, via the exit futex address pointing at the lock.
         * This needs to happen after any possible calls to LOCK() that might
-        * skip locking if libc.threads_minus_1 is zero. */
-       libc.threads_minus_1--;
+        * skip locking if process appears single-threaded. */
+       if (!--libc.threads_minus_1) libc.need_locks = -1;
        self->next->prev = self->prev;
        self->prev->next = self->next;
        self->prev = self->next = self;
@@ -339,7 +339,7 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att
                ~(1UL<<((SIGCANCEL-1)%(8*sizeof(long))));
 
        __tl_lock();
-       libc.threads_minus_1++;
+       if (!libc.threads_minus_1++) libc.need_locks = 1;
        ret = __clone((c11 ? start_c11 : start), stack, flags, args, &new->tid, TP_ADJ(new), &__thread_list_lock);
 
        /* All clone failures translate to EAGAIN. If explicit scheduling
@@ -363,7 +363,7 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att
                new->next->prev = new;
                new->prev->next = new;
        } else {
-               libc.threads_minus_1--;
+               if (!--libc.threads_minus_1) libc.need_locks = 0;
        }
        __tl_unlock();
        __restore_sigs(&set);