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eventpoll: add EPOLL_URING_WAKE poll wakeup flag

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[ Upstream commit caf1aeaffc ]

We can have dependencies between epoll and io_uring. Consider an epoll
context, identified by the epfd file descriptor, and an io_uring file
descriptor identified by iofd. If we add iofd to the epfd context, and
arm a multishot poll request for epfd with iofd, then the multishot
poll request will repeatedly trigger and generate events until terminated
by CQ ring overflow. This isn't a desired behavior.

Add EPOLL_URING so that io_uring can pass it in as part of the poll wakeup
key, and io_uring can check for that to detect a potential recursive
invocation.

Cc: stable@vger.kernel.org # 6.0
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Jens Axboe
2022-11-20 10:10:53 -07:00
committed by Greg Kroah-Hartman
parent a9aa4aa7a5
commit a2d8ff00a7
2 changed files with 16 additions and 8 deletions
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6
include/uapi/linux/eventpoll.h
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@@ -41,6 +41,12 @@
#define EPOLLMSG (__force __poll_t)0x00000400
#define EPOLLRDHUP (__force __poll_t)0x00002000
/*
* Internal flag - wakeup generated by io_uring, used to detect recursion back
* into the io_uring poll handler.
*/
#define EPOLL_URING_WAKE ((__force __poll_t)(1U << 27))
/* Set exclusive wakeup mode for the target file descriptor */
#define EPOLLEXCLUSIVE ((__force __poll_t)(1U << 28))