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binder: use wake_up_pollfree() 

wake_up_poll() uses nr_exclusive=1, so it's not guaranteed to wake up
all exclusive waiters.  Yet, POLLFREE *must* wake up all waiters.  epoll
and aio poll are fortunately not affected by this, but it's very
fragile.  Thus, the new function wake_up_pollfree() has been introduced.

Convert binder to use wake_up_pollfree().

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Fixes: f5cb779ba1 ("ANDROID: binder: remove waitqueue when thread exits.")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211209010455.42744-3-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers 2021-12-08 17:04:52 -08:00
parent 42288cb44c
commit a880b28a71
1 changed files with 9 additions and 12 deletions
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21
drivers/android/binder.c
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@ -4422,23 +4422,20 @@ static int binder_thread_release(struct binder_proc *proc,
__release(&t->lock);
/*
* If this thread used poll, make sure we remove the waitqueue
* from any epoll data structures holding it with POLLFREE.
* waitqueue_active() is safe to use here because we're holding
* the inner lock.
* If this thread used poll, make sure we remove the waitqueue from any
* poll data structures holding it.
*/
if ((thread->looper & BINDER_LOOPER_STATE_POLL) &&
waitqueue_active(&thread->wait)) {
wake_up_poll(&thread->wait, EPOLLHUP | POLLFREE);
}
if (thread->looper & BINDER_LOOPER_STATE_POLL)
wake_up_pollfree(&thread->wait);
binder_inner_proc_unlock(thread->proc);
/*
* This is needed to avoid races between wake_up_poll() above and
* and ep_remove_waitqueue() called for other reasons (eg the epoll file
* descriptor being closed); ep_remove_waitqueue() holds an RCU read
* lock, so we can be sure it's done after calling synchronize_rcu().
* This is needed to avoid races between wake_up_pollfree() above and
* someone else removing the last entry from the queue for other reasons
* (e.g. ep_remove_wait_queue() being called due to an epoll file
* descriptor being closed). Such other users hold an RCU read lock, so
* we can be sure they're done after we call synchronize_rcu().
*/
if (thread->looper & BINDER_LOOPER_STATE_POLL)
synchronize_rcu();