Handles spurious wake-ups in pthread_join()
Removed 'join_count' from pthread_internal_t and switched to using the flag
PTHREAD_ATTR_FLAG_JOINED to indicate if a thread is being joined. Combined with
a switch to a while loop in pthread_join, this fixes spurious wake-ups but
prevents a thread from being joined multiple times. This is fine for
two reasons:
1) The pthread_join specification allows for undefined behavior when multiple
threads try to join a single thread.
2) There is no thread safe way to allow multiple threads to join a single
thread with the pthread interface. The second thread calling pthread_join
could be pre-empted until the thread is destroyed and its handle reused for
a different thread. Therefore multi-join is always an error.
Bug: https://code.google.com/p/android/issues/detail?id=52255
Change-Id: I8b6784d47620ffdcdbfb14524e7402e21d46c5f7
diff --git a/libc/bionic/pthread_internal.h b/libc/bionic/pthread_internal.h
index 316a14a..e34788b 100644
--- a/libc/bionic/pthread_internal.h
+++ b/libc/bionic/pthread_internal.h
@@ -42,7 +42,6 @@
pid_t tid;
bool allocated_on_heap;
pthread_cond_t join_cond;
- int join_count;
void* return_value;
int internal_flags;
__pthread_cleanup_t* cleanup_stack;
@@ -64,9 +63,18 @@
__LIBC_HIDDEN__ void pthread_key_clean_all(void);
__LIBC_HIDDEN__ void _pthread_internal_remove_locked(pthread_internal_t* thread);
+/* Has the thread been detached by a pthread_join or pthread_detach call? */
#define PTHREAD_ATTR_FLAG_DETACHED 0x00000001
+
+/* Was the thread's stack allocated by the user rather than by us? */
#define PTHREAD_ATTR_FLAG_USER_STACK 0x00000002
+/* Has the thread been joined by another thread? */
+#define PTHREAD_ATTR_FLAG_JOINED 0x00000004
+
+/* Has the thread already exited but not been joined? */
+#define PTHREAD_ATTR_FLAG_ZOMBIE 0x00000008
+
__LIBC_HIDDEN__ extern pthread_internal_t* gThreadList;
__LIBC_HIDDEN__ extern pthread_mutex_t gThreadListLock;