This is a note to let you know that I've just added the patch titled io_uring: don't gate task_work run on TIF_NOTIFY_SIGNAL to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: io_uring-don-t-gate-task_work-run-on-tif_notify_sign.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit a1d18b218b3c9ad3c44f17686ed39780d552a243 Author: Jens Axboe <axboe@xxxxxxxxx> Date: Fri Jan 20 20:50:24 2023 -0700 io_uring: don't gate task_work run on TIF_NOTIFY_SIGNAL 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> 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;