Christian Borntraeger
2017-Nov-21 20:12 UTC
4.14: WARNING: CPU: 4 PID: 2895 at block/blk-mq.c:1144 with virtio-blk (also 4.12 stable)
On 11/21/2017 08:30 PM, Jens Axboe wrote:> On 11/21/2017 12:15 PM, Christian Borntraeger wrote: >> >> >> 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 at lst.de> >>>>>>>> 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 at lst.de> >>>>>>>> Reviewed-by: Jens Axboe <axboe at kernel.dk> >>>>>>>> Cc: Keith Busch <keith.busch at intel.com> >>>>>>>> Cc: linux-block at vger.kernel.org >>>>>>>> Cc: linux-nvme at lists.infradead.org >>>>>>>> Link: http://lkml.kernel.org/r/20170626102058.10200-3-hch at lst.de >>>>>>>> Signed-off-by: Thomas Gleixner <tglx at linutronix.de> >>>>>>>> Cc: Oleksandr Natalenko <oleksandr at natalenko.name> >>>>>>>> Cc: Mike Galbraith <efault at gmx.de> >>>>>>>> Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org> >>>>>>> >>>>>>> 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 > > Try this, basically just a revert.Yes, seems to work. Tested-by: Christian Borntraeger <borntraeger at de.ibm.com> Do you know why the original commit made it into 4.12 stable? After all it has no Fixes tag and no cc stable-> > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 11097477eeab..bc1950fa9ef6 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -37,6 +37,9 @@ > #include "blk-wbt.h" > #include "blk-mq-sched.h" > > +static DEFINE_MUTEX(all_q_mutex); > +static LIST_HEAD(all_q_list); > + > 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); > @@ -2114,8 +2117,8 @@ static void blk_mq_init_cpu_queues(struct request_queue *q, > INIT_LIST_HEAD(&__ctx->rq_list); > __ctx->queue = q; > > - /* If the cpu isn't present, the cpu is mapped to first hctx */ > - if (!cpu_present(i)) > + /* If the cpu isn't online, the cpu is mapped to first hctx */ > + if (!cpu_online(i)) > continue; > > hctx = blk_mq_map_queue(q, i); > @@ -2158,7 +2161,8 @@ static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set, > } > } > > -static void blk_mq_map_swqueue(struct request_queue *q) > +static void blk_mq_map_swqueue(struct request_queue *q, > + const struct cpumask *online_mask) > { > unsigned int i, hctx_idx; > struct blk_mq_hw_ctx *hctx; > @@ -2176,11 +2180,13 @@ static void blk_mq_map_swqueue(struct request_queue *q) > } > > /* > - * Map software to hardware queues. > - * > - * If the cpu isn't present, the cpu is mapped to first hctx. > + * Map software to hardware queues > */ > - for_each_present_cpu(i) { > + for_each_possible_cpu(i) { > + /* If the cpu isn't online, the cpu is mapped to first hctx */ > + if (!cpumask_test_cpu(i, online_mask)) > + continue; > + > hctx_idx = q->mq_map[i]; > /* unmapped hw queue can be remapped after CPU topo changed */ > if (!set->tags[hctx_idx] && > @@ -2495,8 +2501,16 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, > blk_queue_softirq_done(q, set->ops->complete); > > blk_mq_init_cpu_queues(q, set->nr_hw_queues); > + > + get_online_cpus(); > + mutex_lock(&all_q_mutex); > + > + list_add_tail(&q->all_q_node, &all_q_list); > blk_mq_add_queue_tag_set(set, q); > - blk_mq_map_swqueue(q); > + blk_mq_map_swqueue(q, cpu_online_mask); > + > + mutex_unlock(&all_q_mutex); > + put_online_cpus(); > > if (!(set->flags & BLK_MQ_F_NO_SCHED)) { > int ret; > @@ -2522,12 +2536,18 @@ void blk_mq_free_queue(struct request_queue *q) > { > struct blk_mq_tag_set *set = q->tag_set; > > + mutex_lock(&all_q_mutex); > + list_del_init(&q->all_q_node); > + mutex_unlock(&all_q_mutex); > + > blk_mq_del_queue_tag_set(q); > + > blk_mq_exit_hw_queues(q, set, set->nr_hw_queues); > } > > /* Basically redo blk_mq_init_queue with queue frozen */ > -static void blk_mq_queue_reinit(struct request_queue *q) > +static void blk_mq_queue_reinit(struct request_queue *q, > + const struct cpumask *online_mask) > { > WARN_ON_ONCE(!atomic_read(&q->mq_freeze_depth)); > > @@ -2539,12 +2559,76 @@ static void blk_mq_queue_reinit(struct request_queue *q) > * we should change hctx numa_node according to the new topology (this > * involves freeing and re-allocating memory, worth doing?) > */ > - blk_mq_map_swqueue(q); > + blk_mq_map_swqueue(q, online_mask); > > blk_mq_sysfs_register(q); > blk_mq_debugfs_register_hctxs(q); > } > > +/* > + * New online cpumask which is going to be set in this hotplug event. > + * Declare this cpumasks as global as cpu-hotplug operation is invoked > + * one-by-one and dynamically allocating this could result in a failure. > + */ > +static struct cpumask cpuhp_online_new; > + > +static void blk_mq_queue_reinit_work(void) > +{ > + struct request_queue *q; > + > + mutex_lock(&all_q_mutex); > + /* > + * We need to freeze and reinit all existing queues. Freezing > + * involves synchronous wait for an RCU grace period and doing it > + * one by one may take a long time. Start freezing all queues in > + * one swoop and then wait for the completions so that freezing can > + * take place in parallel. > + */ > + list_for_each_entry(q, &all_q_list, all_q_node) > + blk_freeze_queue_start(q); > + list_for_each_entry(q, &all_q_list, all_q_node) > + blk_mq_freeze_queue_wait(q); > + > + list_for_each_entry(q, &all_q_list, all_q_node) > + blk_mq_queue_reinit(q, &cpuhp_online_new); > + > + list_for_each_entry(q, &all_q_list, all_q_node) > + blk_mq_unfreeze_queue(q); > + > + mutex_unlock(&all_q_mutex); > +} > + > +static int blk_mq_queue_reinit_dead(unsigned int cpu) > +{ > + cpumask_copy(&cpuhp_online_new, cpu_online_mask); > + blk_mq_queue_reinit_work(); > + return 0; > +} > + > +/* > + * Before hotadded cpu starts handling requests, new mappings must be > + * established. Otherwise, these requests in hw queue might never be > + * dispatched. > + * > + * For example, there is a single hw queue (hctx) and two CPU queues (ctx0 > + * for CPU0, and ctx1 for CPU1). > + * > + * Now CPU1 is just onlined and a request is inserted into ctx1->rq_list > + * and set bit0 in pending bitmap as ctx1->index_hw is still zero. > + * > + * And then while running hw queue, blk_mq_flush_busy_ctxs() finds bit0 is set > + * in pending bitmap and tries to retrieve requests in hctx->ctxs[0]->rq_list. > + * But htx->ctxs[0] is a pointer to ctx0, so the request in ctx1->rq_list is > + * ignored. > + */ > +static int blk_mq_queue_reinit_prepare(unsigned int cpu) > +{ > + cpumask_copy(&cpuhp_online_new, cpu_online_mask); > + cpumask_set_cpu(cpu, &cpuhp_online_new); > + blk_mq_queue_reinit_work(); > + return 0; > +} > + > static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set) > { > int i; > @@ -2757,7 +2841,7 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, > blk_mq_update_queue_map(set); > list_for_each_entry(q, &set->tag_list, tag_set_list) { > blk_mq_realloc_hw_ctxs(set, q); > - blk_mq_queue_reinit(q); > + blk_mq_queue_reinit(q, cpu_online_mask); > } > > list_for_each_entry(q, &set->tag_list, tag_set_list) > @@ -2966,6 +3050,16 @@ static bool blk_mq_poll(struct request_queue *q, blk_qc_t cookie) > return __blk_mq_poll(hctx, rq); > } > > +void blk_mq_disable_hotplug(void) > +{ > + mutex_lock(&all_q_mutex); > +} > + > +void blk_mq_enable_hotplug(void) > +{ > + mutex_unlock(&all_q_mutex); > +} > + > static int __init blk_mq_init(void) > { > /* > @@ -2976,6 +3070,10 @@ static int __init blk_mq_init(void) > > cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL, > blk_mq_hctx_notify_dead); > + > + cpuhp_setup_state_nocalls(CPUHP_BLK_MQ_PREPARE, "block/mq:prepare", > + blk_mq_queue_reinit_prepare, > + blk_mq_queue_reinit_dead); > return 0; > } > subsys_initcall(blk_mq_init); > diff --git a/block/blk-mq.h b/block/blk-mq.h > index 6c7c3ff5bf62..83b13ef1915e 100644 > --- a/block/blk-mq.h > +++ b/block/blk-mq.h > @@ -59,6 +59,11 @@ void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, > void blk_mq_request_bypass_insert(struct request *rq, bool run_queue); > void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx, > struct list_head *list); > +/* > + * CPU hotplug helpers > + */ > +void blk_mq_enable_hotplug(void); > +void blk_mq_disable_hotplug(void); > > /* > * CPU -> queue mappings > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h > index 201ab7267986..c31d4e3bf6d0 100644 > --- a/include/linux/cpuhotplug.h > +++ b/include/linux/cpuhotplug.h > @@ -76,6 +76,7 @@ enum cpuhp_state { > CPUHP_XEN_EVTCHN_PREPARE, > CPUHP_ARM_SHMOBILE_SCU_PREPARE, > CPUHP_SH_SH3X_PREPARE, > + CPUHP_BLK_MQ_PREPARE, > CPUHP_NET_FLOW_PREPARE, > CPUHP_TOPOLOGY_PREPARE, > CPUHP_NET_IUCV_PREPARE, >
Jens Axboe
2017-Nov-21 20:14 UTC
4.14: WARNING: CPU: 4 PID: 2895 at block/blk-mq.c:1144 with virtio-blk (also 4.12 stable)
On 11/21/2017 01:12 PM, Christian Borntraeger wrote:> > > On 11/21/2017 08:30 PM, Jens Axboe wrote: >> On 11/21/2017 12:15 PM, Christian Borntraeger wrote: >>> >>> >>> 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 at lst.de> >>>>>>>>> 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 at lst.de> >>>>>>>>> Reviewed-by: Jens Axboe <axboe at kernel.dk> >>>>>>>>> Cc: Keith Busch <keith.busch at intel.com> >>>>>>>>> Cc: linux-block at vger.kernel.org >>>>>>>>> Cc: linux-nvme at lists.infradead.org >>>>>>>>> Link: http://lkml.kernel.org/r/20170626102058.10200-3-hch at lst.de >>>>>>>>> Signed-off-by: Thomas Gleixner <tglx at linutronix.de> >>>>>>>>> Cc: Oleksandr Natalenko <oleksandr at natalenko.name> >>>>>>>>> Cc: Mike Galbraith <efault at gmx.de> >>>>>>>>> Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org> >>>>>>>> >>>>>>>> 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 >> >> Try this, basically just a revert. > > Yes, seems to work. > > Tested-by: Christian Borntraeger <borntraeger at de.ibm.com>Great, thanks for testing.> Do you know why the original commit made it into 4.12 stable? After all > it has no Fixes tag and no cc stable-I was wondering the same thing when you said it was in 4.12.stable and not in 4.12 release. That patch should absolutely not have gone into stable, it's not marked as such and it's not fixing a problem that is stable worthy. In fact, it's causing a regression... Greg? Upstream commit is mentioned higher up, start of the email. -- Jens Axboe
Christian Borntraeger
2017-Nov-21 20:19 UTC
4.14: WARNING: CPU: 4 PID: 2895 at block/blk-mq.c:1144 with virtio-blk (also 4.12 stable)
On 11/21/2017 09:14 PM, Jens Axboe wrote:> On 11/21/2017 01:12 PM, Christian Borntraeger wrote: >> >> >> On 11/21/2017 08:30 PM, Jens Axboe wrote: >>> On 11/21/2017 12:15 PM, Christian Borntraeger wrote: >>>> >>>> >>>> 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 at lst.de> >>>>>>>>>> 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 at lst.de> >>>>>>>>>> Reviewed-by: Jens Axboe <axboe at kernel.dk> >>>>>>>>>> Cc: Keith Busch <keith.busch at intel.com> >>>>>>>>>> Cc: linux-block at vger.kernel.org >>>>>>>>>> Cc: linux-nvme at lists.infradead.org >>>>>>>>>> Link: http://lkml.kernel.org/r/20170626102058.10200-3-hch at lst.de >>>>>>>>>> Signed-off-by: Thomas Gleixner <tglx at linutronix.de> >>>>>>>>>> Cc: Oleksandr Natalenko <oleksandr at natalenko.name> >>>>>>>>>> Cc: Mike Galbraith <efault at gmx.de> >>>>>>>>>> Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org> >>>>>>>>> >>>>>>>>> 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 >>> >>> Try this, basically just a revert. >> >> Yes, seems to work. >> >> Tested-by: Christian Borntraeger <borntraeger at de.ibm.com> > > Great, thanks for testing. > >> Do you know why the original commit made it into 4.12 stable? After all >> it has no Fixes tag and no cc stable- > > I was wondering the same thing when you said it was in 4.12.stable and > not in 4.12 release. That patch should absolutely not have gone into > stable, it's not marked as such and it's not fixing a problem that is > stable worthy. In fact, it's causing a regression... > > Greg? Upstream commit is mentioned higher up, start of the email. >Forgot to cc Greg?
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