On 10/25/19 12:13 PM, Pavel Begunkov wrote: > On 25/10/2019 19:57, Jens Axboe wrote: >> On 10/25/19 10:55 AM, Pavel Begunkov wrote: >>> On 25/10/2019 19:44, Jens Axboe wrote: >>>> On 10/25/19 10:40 AM, Pavel Begunkov wrote: >>>>> On 25/10/2019 19:32, Jens Axboe wrote: >>>>>> On 10/25/19 10:27 AM, Jens Axboe wrote: >>>>>>> On 10/25/19 10:21 AM, Pavel Begunkov wrote: >>>>>>>> On 25/10/2019 19:03, Jens Axboe wrote: >>>>>>>>> On 10/25/19 3:55 AM, Pavel Begunkov wrote: >>>>>>>>>> I found 2 problems with __io_sequence_defer(). >>>>>>>>>> >>>>>>>>>> 1. it uses @sq_dropped, but doesn't consider @cq_overflow >>>>>>>>>> 2. @sq_dropped and @cq_overflow are write-shared with userspace, so >>>>>>>>>> it can be maliciously changed. >>>>>>>>>> >>>>>>>>>> see sent liburing test (test/defer *_hung()), which left an unkillable >>>>>>>>>> process for me >>>>>>>>> >>>>>>>>> OK, how about the below. I'll split this in two, as it's really two >>>>>>>>> separate fixes. >>>>>>>> cached_sq_dropped is good, but I was concerned about cached_cq_overflow. >>>>>>>> io_cqring_fill_event() can be called in async, so shouldn't we do some >>>>>>>> synchronisation then? >>>>>>> >>>>>>> We should probably make it an atomic just to be on the safe side, I'll >>>>>>> update the series. >>>>>> >>>>>> Here we go, patch 1: >>>>>> >>>>>> http://git.kernel.dk/cgit/linux-block/commit/?h=for-linus&id=f2a241f596ed9e12b7c8f960e79ccda8053ea294 >>>>>> >>>>>> patch 2: >>>>>> >>>>>> http://git.kernel.dk/cgit/linux-block/commit/?h=for-linus&id=b7d0297d2df5bfa0d1ecf9d6c66d23676751ef6a >>>>>> >>>>> 1. submit rqs (not yet completed) >>>>> 2. poll_list is empty, inflight = 0 >>>>> 3. async completed and placed into poll_list >>>>> >>>>> So, poll_list is not empty, but we won't get to polling again. >>>>> At least until someone submitted something. >>>> >>>> But if they are issued, the will sit in ->poll_list as well. That list >>>> holds both "submitted, but pending" and completed entries. >>>> >>> Missed it, then should work. Thanks! >> >> Glad we agree :-) >> >>>> + ret = iters = 0; >>> A small suggestion, could we just initialise it in declaration >>> to be a bit more concise? >>> e.g. int ret = 0, iters = 0; >>> >>> Reviewed-by: Pavel Begunkov <asml.silence@xxxxxxxxx> >>> And let me test it as both patches are ready. >> >> Sure, I'll make that change and add your reviewed-by. Thanks! >> > Stress tested, works well! > > Tested-by: Pavel Begunkov <asml.silence@xxxxxxxxx> Great, thanks for finding these, sending patches, and testing the ones that I fixed! -- Jens Axboe
