On Tue, 2018-02-13 at 09:15 +0100, Paolo Valente wrote: > > > No bfq in the trace, so probably yet another problem stemming from the > interaction between bfq and blk-mq. Hung tasks seem to wait > indefinitely for a tag, and the only bfq patch that affects tag > distribution is: > a52a69ea89dc block, bfq: limit tags for writes and async I/O > > So, for the next step (and as you already decided to do), please retry > after adding the above commit to your initial pair: > patches/block-bfq:-fix-occurrences-of-request-finish-method-s-old-name.patch > patches/block-bfq:-add-requeue-request-hook.patch I did it a bit differently, revert that commit in master, and skip it in 4.15.3 with the otherwise full set first, and saw no hangs testing either. I then added it to the 2 patch series, and was rewarded with... no bloody hang. So it's not as deterministic as it had appeared to be, there's a phase-of-moon factor. Oh. Joy. -Mike