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io_uring: Fix missing smp_mb() in io_cancel_async_work() 

The store to req->flags and load req->work_task should not be
reordering in io_cancel_async_work(). We should make sure that
either we store REQ_F_CANCE flag to req->flags or we see the
req->work_task setted in io_sq_wq_submit_work().

Fixes: 1c4404efcf ("io_uring: make sure async workqueue is canceled on exit")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Muchun Song 2020-10-07 11:16:33 +08:00 committed by Greg Kroah-Hartman
parent d9e81b2fb3
commit 75524f7533
1 changed files with 15 additions and 1 deletions
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16
fs/io_uring.c
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@ -2247,6 +2247,12 @@ restart:
if (!ret) {
req->work_task = current;
/*
* Pairs with the smp_store_mb() (B) in
* io_cancel_async_work().
*/
smp_mb(); /* A */
if (req->flags & REQ_F_CANCEL) {
ret = -ECANCELED;
goto end_req;
@ -3725,7 +3731,15 @@ static void io_cancel_async_work(struct io_ring_ctx *ctx,
req = list_first_entry(&ctx->task_list, struct io_kiocb, task_list);
list_del_init(&req->task_list);
req->flags |= REQ_F_CANCEL;
/*
* The below executes an smp_mb(), which matches with the
* smp_mb() (A) in io_sq_wq_submit_work() such that either
* we store REQ_F_CANCEL flag to req->flags or we see the
* req->work_task setted in io_sq_wq_submit_work().
*/
smp_store_mb(req->flags, req->flags | REQ_F_CANCEL); /* B */
if (req->work_task && (!files || req->files == files))
send_sig(SIGINT, req->work_task, 1);
}