On 07/12/2020 16:28, Jens Axboe wrote: > On Sun, Dec 6, 2020 at 3:26 PM Pavel Begunkov <asml.silence@xxxxxxxxx> wrote: >> From: Xiaoguang Wang <xiaoguang.wang@xxxxxxxxxxxxxxxxx> >> >> The reason is that once we got a non EAGAIN error in io_wq_submit_work(), >> we'll complete req by calling io_req_complete(), which will hold completion_lock >> to call io_commit_cqring(), but for polled io, io_iopoll_complete() won't >> hold completion_lock to call io_commit_cqring(), then there maybe concurrent >> access to ctx->defer_list, double free may happen. >> >> To fix this bug, we always let io_iopoll_complete() complete polled io. > > This patch is causing hangs with iopoll testing, if you end up getting > -EAGAIN on request submission. I've dropped it. I fail to understand without debugging how does it happen, especially since it shouldn't even get out of the while in io_wq_submit_work(). Is that something obvious I've missed? > > Reproducible with test/iopoll /dev/somedevice > > where somedevice has a low queue depth and hits request starvation > during the test. > -- Pavel Begunkov
