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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 1/2] io_uring: fix tw list mess-up by adding tw while it's already in tw list
Date: Mon, 13 Sep 2021 00:23:44 +0800	[thread overview]
Message-ID: <20210912162345.51651-2-haoxu@linux.alibaba.com> (raw)
In-Reply-To: <20210912162345.51651-1-haoxu@linux.alibaba.com>

For multishot mode, there may be cases like:
io_poll_task_func()
-> add_wait_queue()
                            async_wake()
                            ->io_req_task_work_add()
                            this one mess up the running task_work list
                            since req->io_task_work.node is in use.

similar situation for req->io_task_work.fallback_node.
Fix it by set node->next = NULL before we run the tw, so that when we
add req back to the wait queue in middle of tw running, we can safely
re-add it to the tw list.

Fixes: 7cbf1722d5fc ("io_uring: provide FIFO ordering for task_work")
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
---

 fs/io_uring.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 30d959416eba..c16f6be3d46b 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1216,13 +1216,17 @@ static void io_fallback_req_func(struct work_struct *work)
 	struct io_ring_ctx *ctx = container_of(work, struct io_ring_ctx,
 						fallback_work.work);
 	struct llist_node *node = llist_del_all(&ctx->fallback_llist);
-	struct io_kiocb *req, *tmp;
+	struct io_kiocb *req;
 	bool locked = false;
 
 	percpu_ref_get(&ctx->refs);
-	llist_for_each_entry_safe(req, tmp, node, io_task_work.fallback_node)
+	req = llist_entry(node, struct io_kiocb, io_task_work.fallback_node);
+	while (member_address_is_nonnull(req, io_task_work.fallback_node)) {
+		node = req->io_task_work.fallback_node.next;
+		req->io_task_work.fallback_node.next = NULL;
 		req->io_task_work.func(req, &locked);
-
+		req = llist_entry(node, struct io_kiocb, io_task_work.fallback_node);
+	}
 	if (locked) {
 		if (ctx->submit_state.compl_nr)
 			io_submit_flush_completions(ctx);
@@ -2126,6 +2130,7 @@ static void tctx_task_work(struct callback_head *cb)
 				locked = mutex_trylock(&ctx->uring_lock);
 				percpu_ref_get(&ctx->refs);
 			}
+			node->next = NULL;
 			req->io_task_work.func(req, &locked);
 			node = next;
 		} while (node);
-- 
2.24.4


  reply	other threads:[~2021-09-12 16:23 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-12 16:23 [PATCH 0/2] poll fixes Hao Xu
2021-09-12 16:23 ` Hao Xu [this message]
2021-09-15  9:44   ` [PATCH 1/2] io_uring: fix tw list mess-up by adding tw while it's already in tw list Pavel Begunkov
2021-09-15 10:48     ` Hao Xu
2021-09-26  9:48       ` Hao Xu
2021-09-29 11:16         ` Pavel Begunkov
2021-09-12 16:23 ` [PATCH 2/2] io_uring: fix race between poll completion and cancel_hash insertion Hao Xu
2021-09-15  9:50   ` Pavel Begunkov
2021-09-15 10:49     ` Hao Xu
2021-09-15 10:12   ` Pavel Begunkov
2021-09-15 10:50     ` Hao Xu

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