Make pthread join_state not protected by g_thread_list_lock.
1. Move the representation of thread join_state from pthread.attr.flag
to pthread.join_state. This clarifies thread state change.
2. Use atomic operations for pthread.join_state. So we don't need to
protect it by g_thread_list_lock. g_thread_list_lock will be reduced
to only protect g_thread_list or even removed in further changes.
Bug: 19636317
Change-Id: I31fb143a7c69508c7287307dd3b0776993ec0f43
diff --git a/libc/bionic/pthread_exit.cpp b/libc/bionic/pthread_exit.cpp
index d0d64b0..81cc67b 100644
--- a/libc/bionic/pthread_exit.cpp
+++ b/libc/bionic/pthread_exit.cpp
@@ -87,9 +87,12 @@
thread->alternate_signal_stack = NULL;
}
- bool free_mapped_space = false;
- pthread_mutex_lock(&g_thread_list_lock);
- if ((thread->attr.flags & PTHREAD_ATTR_FLAG_DETACHED) != 0) {
+ ThreadJoinState old_state = THREAD_NOT_JOINED;
+ while (old_state == THREAD_NOT_JOINED &&
+ !atomic_compare_exchange_weak(&thread->join_state, &old_state, THREAD_EXITED_NOT_JOINED)) {
+ }
+
+ if (old_state == THREAD_DETACHED) {
// The thread is detached, no one will use pthread_internal_t after pthread_exit.
// So we can free mapped space, which includes pthread_internal_t and thread stack.
// First make sure that the kernel does not try to clear the tid field
@@ -97,28 +100,25 @@
__set_tid_address(NULL);
// pthread_internal_t is freed below with stack, not here.
+ pthread_mutex_lock(&g_thread_list_lock);
_pthread_internal_remove_locked(thread, false);
- free_mapped_space = true;
- } else {
- // Mark the thread as exiting without freeing pthread_internal_t.
- thread->attr.flags |= PTHREAD_ATTR_FLAG_ZOMBIE;
+ pthread_mutex_unlock(&g_thread_list_lock);
+
+ if (thread->mmap_size != 0) {
+ // We need to free mapped space for detached threads when they exit.
+ // That's not something we can do in C.
+
+ // We don't want to take a signal after we've unmapped the stack.
+ // That's one last thing we can handle in C.
+ sigset_t mask;
+ sigfillset(&mask);
+ sigprocmask(SIG_SETMASK, &mask, NULL);
+
+ _exit_with_stack_teardown(thread->attr.stack_base, thread->mmap_size);
+ }
}
- pthread_mutex_unlock(&g_thread_list_lock);
- if (free_mapped_space && thread->mmap_size != 0) {
- // We need to free mapped space for detached threads when they exit.
- // That's not something we can do in C.
-
- // We don't want to take a signal after we've unmapped the stack.
- // That's one last thing we can handle in C.
- sigset_t mask;
- sigfillset(&mask);
- sigprocmask(SIG_SETMASK, &mask, NULL);
-
- _exit_with_stack_teardown(thread->attr.stack_base, thread->mmap_size);
- } else {
- // No need to free mapped space. Either there was no space mapped, or it is left for
- // the pthread_join caller to clean up.
- __exit(0);
- }
+ // No need to free mapped space. Either there was no space mapped, or it is left for
+ // the pthread_join caller to clean up.
+ __exit(0);
}