On 12/8/20 12:12 PM, Pavel Begunkov wrote: > 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? I didn't have time to look into it, and haven't yet, just reporting that it very reliably fails (and under what conditions). -- Jens Axboe
