On 3/17/24 4:07 PM, Jens Axboe wrote: > On 3/17/24 3:51 PM, Jens Axboe wrote: >> On 3/17/24 3:47 PM, Pavel Begunkov wrote: >>> On 3/17/24 21:34, Pavel Begunkov wrote: >>>> On 3/17/24 21:32, Jens Axboe wrote: >>>>> On 3/17/24 3:29 PM, Pavel Begunkov wrote: >>>>>> On 3/17/24 21:24, Jens Axboe wrote: >>>>>>> On 3/17/24 2:55 PM, Pavel Begunkov wrote: >>>>>>>> On 3/16/24 13:56, Ming Lei wrote: >>>>>>>>> On Sat, Mar 16, 2024 at 01:27:17PM +0000, Pavel Begunkov wrote: >>>>>>>>>> On 3/16/24 11:52, Ming Lei wrote: >>>>>>>>>>> On Fri, Mar 15, 2024 at 04:53:21PM -0600, Jens Axboe wrote: >>>>>>>>> >>>>>>>>> ... >>>>>>>>> >>>>>>>>>>> The following two error can be triggered with this patchset >>>>>>>>>>> when running some ublk stress test(io vs. deletion). And not see >>>>>>>>>>> such failures after reverting the 11 patches. >>>>>>>>>> >>>>>>>>>> I suppose it's with the fix from yesterday. How can I >>>>>>>>>> reproduce it, blktests? >>>>>>>>> >>>>>>>>> Yeah, it needs yesterday's fix. >>>>>>>>> >>>>>>>>> You may need to run this test multiple times for triggering the problem: >>>>>>>> >>>>>>>> Thanks for all the testing. I've tried it, all ublk/generic tests hang >>>>>>>> in userspace waiting for CQEs but no complaints from the kernel. >>>>>>>> However, it seems the branch is buggy even without my patches, I >>>>>>>> consistently (5-15 minutes of running in a slow VM) hit page underflow >>>>>>>> by running liburing tests. Not sure what is that yet, but might also >>>>>>>> be the reason. >>>>>>> >>>>>>> Hmm odd, there's nothing in there but your series and then the >>>>>>> io_uring-6.9 bits pulled in. Maybe it hit an unfortunate point in the >>>>>>> merge window -git cycle? Does it happen with io_uring-6.9 as well? I >>>>>>> haven't seen anything odd. >>>>>> >>>>>> Need to test io_uring-6.9. I actually checked the branch twice, both >>>>>> with the issue, and by full recompilation and config prompts I assumed >>>>>> you pulled something in between (maybe not). >>>>>> >>>>>> And yeah, I can't confirm it's specifically an io_uring bug, the >>>>>> stack trace is usually some unmap or task exit, sometimes it only >>>>>> shows when you try to shutdown the VM after tests. >>>>> >>>>> Funky. I just ran a bunch of loops of liburing tests and Ming's ublksrv >>>>> test case as well on io_uring-6.9 and it all worked fine. Trying >>>>> liburing tests on for-6.10/io_uring as well now, but didn't see anything >>>>> the other times I ran it. In any case, once you repost I'll rebase and >>>>> then let's see if it hits again. >>>>> >>>>> Did you run with KASAN enabled >>>> >>>> Yes, it's a debug kernel, full on KASANs, lockdeps and so >>> >>> And another note, I triggered it once (IIRC on shutdown) with ublk >>> tests only w/o liburing/tests, likely limits it to either the core >>> io_uring infra or non-io_uring bugs. >> >> Been running on for-6.10/io_uring, and the only odd thing I see is that >> the test output tends to stall here: >> >> Running test read-before-exit.t >> >> which then either leads to a connection disconnect from my ssh into that >> vm, or just a long delay and then it picks up again. This did not happen >> with io_uring-6.9. >> >> Maybe related? At least it's something new. Just checked again, and yeah >> it seems to totally lock up the vm while that is running. Will try a >> quick bisect of that series. > > Seems to be triggered by the top of branch patch in there, my poll and > timeout special casing. While the above test case runs with that commit, > it'll freeze the host. Had a feeling this was the busy looping off cancelations, and flushing the fallback task_work seems to fix it. I'll check more tomorrow. diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index a2cb8da3cc33..f1d3c5e065e9 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -3242,6 +3242,8 @@ static __cold bool io_uring_try_cancel_requests(struct io_ring_ctx *ctx, ret |= io_kill_timeouts(ctx, task, cancel_all); if (task) ret |= io_run_task_work() > 0; + else if (ret) + flush_delayed_work(&ctx->fallback_work); return ret; } -- Jens Axboe
