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From: Hao Xu <haoxu@linux.alibaba.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: io-uring@vger.kernel.org, Pavel Begunkov <asml.silence@gmail.com>,
	Joseph Qi <joseph.qi@linux.alibaba.com>
Subject: [PATCH 3/5] io_uring: fix race between poll completion and cancel_hash insertion
Date: Sat, 18 Sep 2021 03:38:18 +0800	[thread overview]
Message-ID: <20210917193820.224671-4-haoxu@linux.alibaba.com> (raw)
In-Reply-To: <20210917193820.224671-1-haoxu@linux.alibaba.com>

If poll arming and poll completion runs parallelly, there maybe races.
For instance, run io_poll_add in iowq and io_poll_task_func in original
context, then:
             iowq                          original context
  io_poll_add
    vfs_poll
     (interruption happens
      tw queued to original
      context)                              io_poll_task_func
                                              generate cqe
                                              del from cancel_hash[]
    if !poll.done
      insert to cancel_hash[]

The entry left in cancel_hash[], similar case for fast poll.
Fix it by set poll.done = true when del from cancel_hash[].

Fixes: 5082620fb2ca ("io_uring: terminate multishot poll for CQ ring overflow")
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
---
 fs/io_uring.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 6ea7d4003499..02425022c3b0 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5340,10 +5340,8 @@ static bool __io_poll_complete(struct io_kiocb *req, __poll_t mask)
 	}
 	if (req->poll.events & EPOLLONESHOT)
 		flags = 0;
-	if (!io_cqring_fill_event(ctx, req->user_data, error, flags)) {
-		req->poll.done = true;
+	if (!io_cqring_fill_event(ctx, req->user_data, error, flags))
 		flags = 0;
-	}
 	if (flags & IORING_CQE_F_MORE)
 		ctx->cq_extra++;
 
@@ -5374,6 +5372,7 @@ static void io_poll_task_func(struct io_kiocb *req, bool *locked)
 		if (done) {
 			io_poll_remove_double(req);
 			hash_del(&req->hash_node);
+			req->poll.done = true;
 		} else {
 			req->result = 0;
 			add_wait_queue(req->poll.head, &req->poll.wait);
@@ -5511,6 +5510,7 @@ static void io_async_task_func(struct io_kiocb *req, bool *locked)
 
 	hash_del(&req->hash_node);
 	io_poll_remove_double(req);
+	apoll->poll.done = true;
 	spin_unlock(&ctx->completion_lock);
 
 	if (!READ_ONCE(apoll->poll.canceled))
-- 
2.24.4


  parent reply	other threads:[~2021-09-17 19:38 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-17 19:38 [RFC 0/5] leverage completion cache for poll requests Hao Xu
2021-09-17 19:38 ` [PATCH 1/5] io_uring: return boolean value for io_alloc_async_data Hao Xu
2021-09-17 19:38 ` [PATCH 2/5] io_uring: code clean for io_poll_complete() Hao Xu
2021-09-17 19:38 ` Hao Xu [this message]
2021-09-17 19:38 ` [PATCH 4/5] io_uring: fix lacking of EPOLLONESHOT Hao Xu
2021-09-17 19:38 ` [PATCH 5/5] io_uring: leverage completion cache for poll requests Hao Xu
2021-09-17 19:51   ` Hao Xu
2021-09-17 20:39   ` Pavel Begunkov
2021-09-18  6:11     ` Hao Xu
2021-09-19 12:04       ` Pavel Begunkov
2021-09-19 15:52         ` Hao Xu
2021-09-19 16:10           ` Hao Xu
2021-09-17 20:28 ` [RFC 0/5] " Pavel Begunkov

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