Commit 76de6749 authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: further limit non-owner defer-tw cq waiting 



In case of DEFER_TASK_WORK we try to restrict waiters to only one task,
which is also the only submitter; however, we don't do it reliably,
which might be very confusing and backfire in the future. E.g. we
currently allow multiple tasks in io_iopoll_check().

Fixes: c0e0d6ba ("io_uring: add IORING_SETUP_DEFER_TASKRUN")
Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Reviewed-by: default avatarDylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/94c83c0a7fe468260ee2ec31bdb0095d6e874ba2.1662652536.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent ac9e5784

io_uring/io_uring.c

+6 −0
Original line number Diff line number Diff line
@@ -1398,6 +1398,9 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, long min) 
	int ret = 0;

	unsigned long check_cq;



	if (!io_allowed_run_tw(ctx))

		return -EEXIST;



	check_cq = READ_ONCE(ctx->check_cq);

	if (unlikely(check_cq)) {

		if (check_cq & BIT(IO_CHECK_CQ_OVERFLOW_BIT))
@@ -2382,6 +2385,9 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, 
	ktime_t timeout = KTIME_MAX;

	int ret;



	if (!io_allowed_run_tw(ctx))

		return -EEXIST;



	do {

		/* always run at least 1 task work to process local work */

		ret = io_run_task_work_ctx(ctx);

io_uring/io_uring.h

+11 −0
Original line number Diff line number Diff line
@@ -329,4 +329,15 @@ static inline struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx) 
	return container_of(node, struct io_kiocb, comp_list);

}



static inline bool io_allowed_run_tw(struct io_ring_ctx *ctx)

{

	if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN))

		return true;

	if (unlikely(ctx->submitter_task != current)) {

		/* maybe this is before any submissions */

		return !ctx->submitter_task;

	}

	return true;

}



#endif