On 10/2/19 3:56 AM, John Garry wrote: > On 22/08/2019 18:39, John Garry wrote: >> On 12/08/2019 14:43, 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 dead(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 >>> >>> Please comment & review, thanks! >>> >>> V2: >>> - patch4 & patch 5 in V1 have been merged to block tree, so remove >>> them >>> - address comments from John Garry and Minwoo >>> >>> >>> Ming Lei (5): >>> blk-mq: add new state of BLK_MQ_S_INTERNAL_STOPPED >>> blk-mq: add blk-mq flag of BLK_MQ_F_NO_MANAGED_IRQ >>> blk-mq: stop to handle IO before hctx's all CPUs become offline >>> blk-mq: re-submit IO in case that hctx is dead >>> blk-mq: handle requests dispatched from IO scheduler in case that hctx >>> is dead >> >> Hi Ming, >> >> This looks to fix the hotplug issue for me. >> >> Previously I could manufacture a scenario while running fio where I got >> IO timeouts, like this: >> >> root@(none)$ echo 0 > ./sys/devices/system/cpu/cpu0/online >> [ 296.897627] process 891 (fio) no longer affine to cpu0 >> [ 296.898488] process 893 (fio) no longer affine to cpu0 >> [ 296.910270] process 890 (fio) no longer affine to cpu0 >> [ 296.927322] IRQ 775: no longer affine to CPU0 >> [ 296.932762] CPU0: shutdown >> [ 296.935469] psci: CPU0 killed. >> root@(none)$ [ 326.971962] sas: Enter sas_scsi_recover_host busy: 61 >> failed: 61 >> [ 326.977978] sas: sas_scsi_find_task: aborting task 0x00000000e2cdc79b >> root@(none)$ [ 333.047964] hisi_sas_v3_hw 0000:74:02.0: internal task >> abort: timeout and not done. >> [ 333.055616] hisi_sas_v3_hw 0000:74:02.0: abort task: internal abort (-5) >> [ 333.062306] sas: sas_scsi_find_task: querying task 0x00000000e2cdc79b >> [ 333.068776] sas: sas_scsi_find_task: task 0x00000000e2cdc79b not at LU >> [ 333.075295] sas: task 0x00000000e2cdc79b is not at LU: I_T recover >> [ 333.081464] sas: I_T nexus reset for dev 5000c500a7b95a49 >> >> Please notice the 30-second delay for the SCSI IO timeout. >> >> And now I don't see it; here's a sample for irq shutdown: >> root@(none)$ echo 0 > ./sys/devices/system/cpu/cpu0/online >> [ 344.608148] process 849 (fio) no longer affine to cpu0 >> [ 344.608639] process 848 (fio) no longer affine to cpu0 >> [ 344.609454] process 850 (fio) no longer affine to cpu0 >> [ 344.643481] process 847 (fio) no longer affine to cpu0 >> [ 346.213842] IRQ 775: no longer affine to CPU0 >> [ 346.219712] CPU0: shutdown >> [ 346.222425] psci: CPU0 killed. >> >> Please notice the ~1.5s pause, which would be the queue draining. >> >> So FWIW: >> Tested-by: John Garry <john.garry@xxxxxxxxxx> >> >> JFYI, I tested on 5.3-rc5 and cherry-picked >> https://github.com/ming1/linux/commit/0d2cd3c99bb0fe81d2c0ca5d68e02bdc4521d4d6 >> and "blk-mq: add callback of .cleanup_rq". >> >> Cheers, >> John > > Hi Jens, > > I don't mean to be pushy, but can we consider to get these patches from > Ming merged? > > As above, I tested on my SCSI driver and it works. I also tested on an > NVMe disk, and it solves the condition which generates this message: > root@(none)$ echo 0 > /sys/devices/system/cpu/cpu2/online > [ 465.635960] CPU2: shutdown > [ 465.638662] psci: CPU2 killed. > [ 111.381653] nvme nvme0: I/O 705 QID 18 timeout, completion polled > > (that's on top off v5.4-rc1) Ming, can you repost the series? -- Jens Axboe
