From: Jens Axboe <axboe@xxxxxxxxx>
[ Upstream commit 4464853277d0ccdb9914608dd1332f0fa2f9846f ]
Pass in EPOLL_URING_WAKE when signaling eventfd or doing poll related
wakups, so that we can check for a circular event dependency between
eventfd and epoll. If this flag is set when our wakeup handlers are
called, then we know we have a dependency that needs to terminate
multishot requests.
eventfd and epoll are the only such possible dependencies.
Cc: stable@xxxxxxxxxxxxxxx # 6.0
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
io_uring/io_uring.c | 27 ++++++++++++++++++++-------
1 file changed, 20 insertions(+), 7 deletions(-)
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 9a01188ff45a..d855e668f37c 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1629,13 +1629,15 @@ static void io_cqring_ev_posted(struct io_ring_ctx *ctx)
* wake as many waiters as we need to.
*/
if (wq_has_sleeper(&ctx->cq_wait))
- wake_up_all(&ctx->cq_wait);
+ __wake_up(&ctx->cq_wait, TASK_NORMAL, 0,
+ poll_to_key(EPOLL_URING_WAKE | EPOLLIN));
if (ctx->sq_data && waitqueue_active(&ctx->sq_data->wait))
wake_up(&ctx->sq_data->wait);
if (io_should_trigger_evfd(ctx))
- eventfd_signal(ctx->cq_ev_fd, 1);
+ eventfd_signal_mask(ctx->cq_ev_fd, 1, EPOLL_URING_WAKE);
if (waitqueue_active(&ctx->poll_wait))
- wake_up_interruptible(&ctx->poll_wait);
+ __wake_up(&ctx->poll_wait, TASK_INTERRUPTIBLE, 0,
+ poll_to_key(EPOLL_URING_WAKE | EPOLLIN));
}
static void io_cqring_ev_posted_iopoll(struct io_ring_ctx *ctx)
@@ -1645,12 +1647,14 @@ static void io_cqring_ev_posted_iopoll(struct io_ring_ctx *ctx)
if (ctx->flags & IORING_SETUP_SQPOLL) {
if (waitqueue_active(&ctx->cq_wait))
- wake_up_all(&ctx->cq_wait);
+ __wake_up(&ctx->cq_wait, TASK_NORMAL, 0,
+ poll_to_key(EPOLL_URING_WAKE | EPOLLIN));
}
if (io_should_trigger_evfd(ctx))
- eventfd_signal(ctx->cq_ev_fd, 1);
+ eventfd_signal_mask(ctx->cq_ev_fd, 1, EPOLL_URING_WAKE);
if (waitqueue_active(&ctx->poll_wait))
- wake_up_interruptible(&ctx->poll_wait);
+ __wake_up(&ctx->poll_wait, TASK_INTERRUPTIBLE, 0,
+ poll_to_key(EPOLL_URING_WAKE | EPOLLIN));
}
/* Returns true if there are no backlogged entries after the flush */
@@ -5636,8 +5640,17 @@ static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
if (mask && !(mask & poll->events))
return 0;
- if (io_poll_get_ownership(req))
+ if (io_poll_get_ownership(req)) {
+ /*
+ * If we trigger a multishot poll off our own wakeup path,
+ * disable multishot as there is a circular dependency between
+ * CQ posting and triggering the event.
+ */
+ if (mask & EPOLL_URING_WAKE)
+ poll->events |= EPOLLONESHOT;
+
__io_poll_execute(req, mask);
+ }
return 1;
}
--
2.39.0
