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io_uring: clarify io_req_task_cancel() locking

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

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/71099083835f983a1fd73d5a3da6391924da8300.1629920396.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-08-25 20:51:39 +01:00 committed by Jens Axboe
parent 9a10867ae5
commit b18a1a4574
1 changed files with 1 additions and 2 deletions
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3
fs/io_uring.c
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@ -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)))