[PATCH 5.15 027/117] io_uring: dont gate task_work run on TIF_NOTIFY_SIGNAL

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From: Jens Axboe <axboe@xxxxxxxxx>

commit 46a525e199e4037516f7e498c18f065b09df32ac upstream.

This isn't a reliable mechanism to tell if we have task_work pending, we
really should be looking at whether we have any items queued. This is
problematic if forward progress is gated on running said task_work. One
such example is reading from a pipe, where the write side has been closed
right before the read is started. The fput() of the file queues TWA_RESUME
task_work, and we need that task_work to be run before ->release() is
called for the pipe. If ->release() isn't called, then the read will sit
forever waiting on data that will never arise.

Fix this by io_run_task_work() so it checks if we have task_work pending
rather than rely on TIF_NOTIFY_SIGNAL for that. The latter obviously
doesn't work for task_work that is queued without TWA_SIGNAL.

Reported-by: Christiano Haesbaert <haesbaert@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://github.com/axboe/liburing/issues/665
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 io_uring/io-wq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c
index 87bc38b47103..81485c1a9879 100644
--- a/io_uring/io-wq.c
+++ b/io_uring/io-wq.c
@@ -513,7 +513,7 @@ static struct io_wq_work *io_get_next_work(struct io_wqe_acct *acct,
 
 static bool io_flush_signals(void)
 {
-	if (unlikely(test_thread_flag(TIF_NOTIFY_SIGNAL))) {
+	if (test_thread_flag(TIF_NOTIFY_SIGNAL) || current->task_works) {
 		__set_current_state(TASK_RUNNING);
 		tracehook_notify_signal();
 		return true;
-- 
2.39.0






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