On 11/21/2017 07:39 PM, Jens Axboe wrote: > On 11/21/2017 11:27 AM, Jens Axboe wrote: >> On 11/21/2017 11:12 AM, Christian Borntraeger wrote: >>> >>> >>> On 11/21/2017 07:09 PM, Jens Axboe wrote: >>>> On 11/21/2017 10:27 AM, Jens Axboe wrote: >>>>> On 11/21/2017 03:14 AM, Christian Borntraeger wrote: >>>>>> Bisect points to >>>>>> >>>>>> 1b5a7455d345b223d3a4658a9e5fce985b7998c1 is the first bad commit >>>>>> commit 1b5a7455d345b223d3a4658a9e5fce985b7998c1 >>>>>> Author: Christoph Hellwig <hch@xxxxxx> >>>>>> Date: Mon Jun 26 12:20:57 2017 +0200 >>>>>> >>>>>> blk-mq: Create hctx for each present CPU >>>>>> >>>>>> commit 4b855ad37194f7bdbb200ce7a1c7051fecb56a08 upstream. >>>>>> >>>>>> Currently we only create hctx for online CPUs, which can lead to a lot >>>>>> of churn due to frequent soft offline / online operations. Instead >>>>>> allocate one for each present CPU to avoid this and dramatically simplify >>>>>> the code. >>>>>> >>>>>> Signed-off-by: Christoph Hellwig <hch@xxxxxx> >>>>>> Reviewed-by: Jens Axboe <axboe@xxxxxxxxx> >>>>>> Cc: Keith Busch <keith.busch@xxxxxxxxx> >>>>>> Cc: linux-block@xxxxxxxxxxxxxxx >>>>>> Cc: linux-nvme@xxxxxxxxxxxxxxxxxxx >>>>>> Link: http://lkml.kernel.org/r/20170626102058.10200-3-hch@xxxxxx >>>>>> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> >>>>>> Cc: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx> >>>>>> Cc: Mike Galbraith <efault@xxxxxx> >>>>>> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> >>>>> >>>>> I wonder if we're simply not getting the masks updated correctly. I'll >>>>> take a look. >>>> >>>> Can't make it trigger here. We do init for each present CPU, which means >>>> that if I offline a few CPUs here and register a queue, those still show >>>> up as present (just offline) and get mapped accordingly. >>>> >>>> From the looks of it, your setup is different. If the CPU doesn't show >>>> up as present and it gets hotplugged, then I can see how this condition >>>> would trigger. What environment are you running this in? We might have >>>> to re-introduce the cpu hotplug notifier, right now we just monitor >>>> for a dead cpu and handle that. >>> >>> I am not doing a hot unplug and the replug, I use KVM and add a previously >>> not available CPU. >>> >>> in libvirt/virsh speak: >>> <vcpu placement='static' current='1'>4</vcpu> >> >> So that's why we run into problems. It's not present when we load the device, >> but becomes present and online afterwards. >> >> Christoph, we used to handle this just fine, your patch broke it. >> >> I'll see if I can come up with an appropriate fix. > > Can you try the below? It does prevent the crash but it seems that the new CPU is not "used " after the hotplug for mq: output with 2 cpus: /sys/kernel/debug/block/vda /sys/kernel/debug/block/vda/hctx0 /sys/kernel/debug/block/vda/hctx0/cpu0 /sys/kernel/debug/block/vda/hctx0/cpu0/completed /sys/kernel/debug/block/vda/hctx0/cpu0/merged /sys/kernel/debug/block/vda/hctx0/cpu0/dispatched /sys/kernel/debug/block/vda/hctx0/cpu0/rq_list /sys/kernel/debug/block/vda/hctx0/active /sys/kernel/debug/block/vda/hctx0/run /sys/kernel/debug/block/vda/hctx0/queued /sys/kernel/debug/block/vda/hctx0/dispatched /sys/kernel/debug/block/vda/hctx0/io_poll /sys/kernel/debug/block/vda/hctx0/sched_tags_bitmap /sys/kernel/debug/block/vda/hctx0/sched_tags /sys/kernel/debug/block/vda/hctx0/tags_bitmap /sys/kernel/debug/block/vda/hctx0/tags /sys/kernel/debug/block/vda/hctx0/ctx_map /sys/kernel/debug/block/vda/hctx0/busy /sys/kernel/debug/block/vda/hctx0/dispatch /sys/kernel/debug/block/vda/hctx0/flags /sys/kernel/debug/block/vda/hctx0/state /sys/kernel/debug/block/vda/sched /sys/kernel/debug/block/vda/sched/dispatch /sys/kernel/debug/block/vda/sched/starved /sys/kernel/debug/block/vda/sched/batching /sys/kernel/debug/block/vda/sched/write_next_rq /sys/kernel/debug/block/vda/sched/write_fifo_list /sys/kernel/debug/block/vda/sched/read_next_rq /sys/kernel/debug/block/vda/sched/read_fifo_list /sys/kernel/debug/block/vda/write_hints /sys/kernel/debug/block/vda/state /sys/kernel/debug/block/vda/requeue_list /sys/kernel/debug/block/vda/poll_stat > > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index b600463791ec..ab3a66e7bd03 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -40,6 +40,7 @@ > static bool blk_mq_poll(struct request_queue *q, blk_qc_t cookie); > static void blk_mq_poll_stats_start(struct request_queue *q); > static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb); > +static void blk_mq_map_swqueue(struct request_queue *q); > > static int blk_mq_poll_stats_bkt(const struct request *rq) > { > @@ -1947,6 +1950,15 @@ int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags, > return -ENOMEM; > } > > +static int blk_mq_hctx_notify_prepare(unsigned int cpu, struct hlist_node *node) > +{ > + struct blk_mq_hw_ctx *hctx; > + > + hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp); > + blk_mq_map_swqueue(hctx->queue); > + return 0; > +} > + > /* > * 'cpu' is going away. splice any existing rq_list entries from this > * software queue to the hw queue dispatch list, and ensure that it > @@ -1958,7 +1970,7 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node) > struct blk_mq_ctx *ctx; > LIST_HEAD(tmp); > > - hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp_dead); > + hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp); > ctx = __blk_mq_get_ctx(hctx->queue, cpu); > > spin_lock(&ctx->lock); > @@ -1981,8 +1993,7 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node) > > static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx) > { > - cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD, > - &hctx->cpuhp_dead); > + cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_PREPARE, &hctx->cpuhp); > } > > /* hctx->ctxs will be freed in queue's release handler */ > @@ -2039,7 +2050,7 @@ static int blk_mq_init_hctx(struct request_queue *q, > hctx->queue = q; > hctx->flags = set->flags & ~BLK_MQ_F_TAG_SHARED; > > - cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead); > + cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_PREPARE, &hctx->cpuhp); > > hctx->tags = set->tags[hctx_idx]; > > @@ -2974,7 +2987,8 @@ static int __init blk_mq_init(void) > BUILD_BUG_ON((REQ_ATOM_STARTED / BITS_PER_BYTE) != > (REQ_ATOM_COMPLETE / BITS_PER_BYTE)); > > - cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL, > + cpuhp_setup_state_multi(CPUHP_BLK_MQ_PREPARE, "block/mq:prepare", > + blk_mq_hctx_notify_prepare, > blk_mq_hctx_notify_dead); > return 0; > } > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h > index 95c9a5c862e2..a6f03e9464fb 100644 > --- a/include/linux/blk-mq.h > +++ b/include/linux/blk-mq.h > @@ -52,7 +52,7 @@ struct blk_mq_hw_ctx { > > atomic_t nr_active; > > - struct hlist_node cpuhp_dead; > + struct hlist_node cpuhp; > struct kobject kobj; > > unsigned long poll_considered; > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h > index ec32c4c5eb30..28b0fc9229c8 100644 > --- a/include/linux/cpuhotplug.h > +++ b/include/linux/cpuhotplug.h > @@ -48,7 +48,7 @@ enum cpuhp_state { > CPUHP_BLOCK_SOFTIRQ_DEAD, > CPUHP_ACPI_CPUDRV_DEAD, > CPUHP_S390_PFAULT_DEAD, > - CPUHP_BLK_MQ_DEAD, > + CPUHP_BLK_MQ_PREPARE, > CPUHP_FS_BUFF_DEAD, > CPUHP_PRINTK_DEAD, > CPUHP_MM_MEMCQ_DEAD, >
