From: Jens Axboe axboe@kernel.dk
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@haesbaert.org Cc: stable@vger.kernel.org Link: https://github.com/axboe/liburing/issues/665 Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- 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;