From: Jens Axboe axboe@kernel.dk
[ Upstream commit 46a525e199e4037516f7e498c18f065b09df32ac ]
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_uring.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h index 45809ae6f64e..5121b20a9193 100644 --- a/io_uring/io_uring.h +++ b/io_uring/io_uring.h @@ -229,12 +229,12 @@ static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx)
static inline bool io_run_task_work(void) { - if (test_thread_flag(TIF_NOTIFY_SIGNAL)) { + if (task_work_pending(current)) { + if (test_thread_flag(TIF_NOTIFY_SIGNAL)) + clear_notify_signal(); __set_current_state(TASK_RUNNING); - clear_notify_signal(); - if (task_work_pending(current)) - task_work_run(); - return true; + task_work_run(); + return 1; }
return false;