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

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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: c0e0d6ba25 ("io_uring: add IORING_SETUP_DEFER_TASKRUN")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/94c83c0a7fe468260ee2ec31bdb0095d6e874ba2.1662652536.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2022-09-08 16:56:52 +01:00 committed by Jens Axboe
parent ac9e5784bb
commit 76de6749d1
2 changed files with 17 additions and 0 deletions
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6
io_uring/io_uring.c
View File

@ -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);

11
io_uring/io_uring.h
View File

@ -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