From: Jens Axboe axboe@kernel.dk
[ 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@vger.kernel.org # 6.0 Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- io_uring/io_uring.c | 27 ++++++++++++++++++++------- 1 file changed, 20 insertions(+), 7 deletions(-)
--- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -1626,13 +1626,15 @@ static void io_cqring_ev_posted(struct i * 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) @@ -1642,12 +1644,14 @@ static void io_cqring_ev_posted_iopoll(s
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 */ @@ -5477,8 +5481,17 @@ static int io_poll_wake(struct wait_queu 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; }