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Fix bug in pthread_join, pthread_exit, pthread_detach

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pthread_no_op_detach_after_join test from bionic-unit-tests hangs
on x86 emulator. There is a race in the pthread_join, pthread_exit,
pthread_detach functions:
- pthread_join waits for the non-detached thread
- pthread_detach sets the detached flag on that thread
- the thread executes pthread_exit which just kills the now-detached
thread, without sending the join notification.

This patch improves the test so it fails on ARM too, and modifies
pthread_detach to behave more like glibc, not setting the detach state if
called on a thread that's already being joined (but not returning an error).

Change-Id: I87dc688221ce979ef5178753dd63d01ac0b108e6
Signed-off-by: Sergey Melnikov <sergey.melnikov@intel.com>
This commit is contained in:
Sergey Melnikov
2012-10-26 14:06:43 +04:00
committed by Elliott Hughes
parent 4d36b0bd38
commit 10ce96944e
2 changed files with 47 additions and 20 deletions
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33
libc/bionic/pthread.c
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@@ -582,7 +582,7 @@ void pthread_exit(void * retval)
pthread_key_clean_all();
// if the thread is detached, destroy the pthread_internal_t
// otherwise, keep it in memory and signal any joiners
// otherwise, keep it in memory and signal any joiners.
if (thread->attr.flags & PTHREAD_ATTR_FLAG_DETACHED) {
_pthread_internal_remove(thread);
_pthread_internal_free(thread);
@@ -668,8 +668,9 @@ FoundIt:
pthread_cond_wait( &thread->join_cond, &gThreadListLock );
count = --thread->join_count;
}
if (ret_val)
if (ret_val) {
*ret_val = thread->return_value;
}
/* remove thread descriptor when we're the last joiner or when the
* thread was already a zombie.
@@ -686,28 +687,30 @@ int pthread_detach( pthread_t thid )
{
pthread_internal_t* thread;
int result = 0;
int flags;
pthread_mutex_lock(&gThreadListLock);
for (thread = gThreadList; thread != NULL; thread = thread->next)
if (thread == (pthread_internal_t*)thid)
for (thread = gThreadList; thread != NULL; thread = thread->next) {
if (thread == (pthread_internal_t*)thid) {
goto FoundIt;
}
}
result = ESRCH;
goto Exit;
FoundIt:
do {
flags = thread->attr.flags;
if ( flags & PTHREAD_ATTR_FLAG_DETACHED ) {
/* thread is not joinable ! */
result = EINVAL;
goto Exit;
}
if (thread->attr.flags & PTHREAD_ATTR_FLAG_DETACHED) {
result = EINVAL; // Already detached.
goto Exit;
}
while ( __bionic_cmpxchg( flags, flags | PTHREAD_ATTR_FLAG_DETACHED,
(volatile int*)&thread->attr.flags ) != 0 );
if (thread->join_count > 0) {
result = 0; // Already being joined; silently do nothing, like glibc.
goto Exit;
}
thread->attr.flags |= PTHREAD_ATTR_FLAG_DETACHED;
Exit:
pthread_mutex_unlock(&gThreadListLock);
return result;