On 08/12/2020 19:17, Jens Axboe wrote: > 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). Yeah, I get it, asked just in case. I'll see what's going on if Xiaoguang wouldn't handle it before. -- Pavel Begunkov
