Commit b18a1a45 authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: clarify io_req_task_cancel() locking 



It's too easy to forget and misjudge about synchronisation in
io_req_task_cancel(), add a comment clarifying it.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/71099083835f983a1fd73d5a3da6391924da8300.1629920396.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 9a10867a

fs/io_uring.c

+1 −2
Original line number Diff line number Diff line
@@ -2168,7 +2168,7 @@ static void io_req_task_cancel(struct io_kiocb *req, bool *locked) 
{

	struct io_ring_ctx *ctx = req->ctx;



	/* ctx is guaranteed to stay alive while we hold uring_lock */

	/* not needed for normal modes, but SQPOLL depends on it */

	io_tw_lock(ctx, locked);

	io_req_complete_failed(req, req->result);

}
@@ -2177,7 +2177,6 @@ static void io_req_task_submit(struct io_kiocb *req, bool *locked) 
{

	struct io_ring_ctx *ctx = req->ctx;



	/* ctx stays valid until unlock, even if we drop all ours ctx->refs */

	io_tw_lock(ctx, locked);

	/* req->task == current here, checking PF_EXITING is safe */

	if (likely(!(req->task->flags & PF_EXITING)))