On Wed, May 13, 2020 at 08:34:01AM +0100, John Garry wrote: > On 13/05/2020 04:47, Ming Lei wrote: > > Hi, > > > > Thomas mentioned: > > " > > That was the constraint of managed interrupts from the very beginning: > > The driver/subsystem has to quiesce the interrupt line and the associated > > queue _before_ it gets shutdown in CPU unplug and not fiddle with it > > until it's restarted by the core when the CPU is plugged in again. > > " > > > > But no drivers or blk-mq do that before one hctx becomes inactive(all > > CPUs for one hctx are offline), and even it is worse, blk-mq stills tries > > to run hw queue after hctx is dead, see blk_mq_hctx_notify_dead(). > > > > This patchset tries to address the issue by two stages: > > > > 1) add one new cpuhp state of CPUHP_AP_BLK_MQ_ONLINE > > > > - mark the hctx as internal stopped, and drain all in-flight requests > > if the hctx is going to be dead. > > > > 2) re-submit IO in the state of CPUHP_BLK_MQ_DEAD after the hctx becomes dead > > > > - steal bios from the request, and resubmit them via generic_make_request(), > > then these IO will be mapped to other live hctx for dispatch > > > > Thanks John Garry for running lots of tests on arm64 with this patchset > > and co-working on investigating all kinds of issues. > > > > Thanks Christoph's review on V7 & V8. > > > > Please consider it for v5.8. > > > > https://github.com/ming1/linux/commits/v5.7-rc-blk-mq-improve-cpu-hotplug > > > > V11: > > - drop new callback from blk_mq_all_tag_busy_iter, add new helper > > of blk_mq_all_tag_iter (5/12), as suggested by Bart > > - fix request allocation hang in case of queue freeze(11/12), as > > reported by Bart > > > > V10: > > - fix double bio complete in request resubmission(10/11) > > - add tested-by tag > > > > V9: > > - add Reviewed-by tag > > - document more on memory barrier usage between getting driver tag > > and handling cpu offline(7/11) > > - small code cleanup as suggested by Chritoph(7/11) > > - rebase against for-5.8/block(1/11, 2/11) > > V8: > > - add patches to share code with blk_rq_prep_clone > > - code re-organization as suggested by Christoph, most of them are > > in 04/11, 10/11 > > - add reviewed-by tag > > > > V7: > > - fix updating .nr_active in get_driver_tag > > - add hctx->cpumask check in cpuhp handler > > - only drain requests which tag is >= 0 > > - pass more aggressive cpuhotplug&io test > > > > V6: > > - simplify getting driver tag, so that we can drain in-flight > > requests correctly without using synchronize_rcu() > > - handle re-submission of flush & passthrough request correctly > > > > V5: > > - rename BLK_MQ_S_INTERNAL_STOPPED as BLK_MQ_S_INACTIVE > > - re-factor code for re-submit requests in cpu dead hotplug handler > > - address requeue corner case > > > > V4: > > - resubmit IOs in dispatch list in case that this hctx is dead > > > > V3: > > - re-organize patch 2 & 3 a bit for addressing Hannes's comment > > - fix patch 4 for avoiding potential deadlock, as found by Hannes > > > > V2: > > - patch4 & patch 5 in V1 have been merged to block tree, so remove > > them > > - address comments from John Garry and Minwoo > > > > > > *** BLURB HERE *** > > :) > > So my tested-by tags have been dropped. I'll test again, since the changes > are non-trivial. > > Tip commit of > https://github.com/ming1/linux/commits/v5.7-rc-blk-mq-improve-cpu-hotplug at > this moment is b55e97a4 Hi John, I just sent out V12 of patch 10/12, which can kill the warning on BLK_MQ_REQ_FORCE, and the warning is harmless actually. And the above git branch has been updated too. Please retest and update with us. Thanks, Ming
