在 2021/9/15 下午5:50, Pavel Begunkov 写道:
On 9/12/21 5:23 PM, Hao Xu wrote:
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[].
Sounds like a valid concern. And the code looks good, but one
of two patches crashed the kernel somewhere in io_read().
./232c93d07b74-test
I'll run it too, didn't meet that when I did the test.
will be retesting
Signed-off-by: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx>
---
Didn't find the exact commit to add Fixes: for..
That's ok. Maybe you can find which kernel versions are
affected? So we can add stable and specify where it should
be backported? E.g.
Sure, will do that.
Cc: stable@xxxxxxxxxxxxxxx # 5.12+
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 c16f6be3d46b..988679e5063f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5118,10 +5118,8 @@ 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++;
@@ -5152,6 +5150,7 @@ 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);
@@ -5289,6 +5288,7 @@ static void io_async_task_func(struct io_kiocb *req, bool *locked)
hash_del(&req->hash_node);
io_poll_remove_double(req);
+ req->poll.done = true;
spin_unlock(&ctx->completion_lock);
if (!READ_ONCE(apoll->poll.canceled))
