On Tue, Jul 16, 2019 at 11:03:14AM +0800, John Garry wrote: > 在 12/07/2019 10:47, Ming Lei 写道: > > Most of blk-mq drivers depend on managed IRQ's auto-affinity to setup > > up queue mapping. Thomas mentioned the following point[1]: > > > > " > > 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. > > " > > > > However, current blk-mq implementation doesn't quiesce hw queue before > > the last CPU in the hctx is shutdown. Even worse, CPUHP_BLK_MQ_DEAD is > > one cpuhp state handled after the CPU is down, so there isn't any chance > > to quiesce hctx for blk-mq wrt. CPU hotplug. > > > > Add new cpuhp state of CPUHP_AP_BLK_MQ_ONLINE for blk-mq to stop queues > > and wait for completion of in-flight requests. > > > > [1] https://lore.kernel.org/linux-block/alpine.DEB.2.21.1904051331270.1802@xxxxxxxxxxxxxxxxxxxxxxx/ > > > > Cc: Bart Van Assche <bvanassche@xxxxxxx> > > Cc: Hannes Reinecke <hare@xxxxxxxx> > > Cc: Christoph Hellwig <hch@xxxxxx> > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > Cc: Keith Busch <keith.busch@xxxxxxxxx> > > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> > > --- > > block/blk-mq-tag.c | 2 +- > > block/blk-mq-tag.h | 2 ++ > > block/blk-mq.c | 67 ++++++++++++++++++++++++++++++++++++++ > > include/linux/blk-mq.h | 1 + > > include/linux/cpuhotplug.h | 1 + > > 5 files changed, 72 insertions(+), 1 deletion(-) > > > > diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c > > index da19f0bc8876..bcefb213ad69 100644 > > --- a/block/blk-mq-tag.c > > +++ b/block/blk-mq-tag.c > > @@ -324,7 +324,7 @@ static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt, > > * true to continue iterating tags, false to stop. > > * @priv: Will be passed as second argument to @fn. > > */ > > -static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, > > +void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, > > busy_tag_iter_fn *fn, void *priv) > > { > > if (tags->nr_reserved_tags) > > diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h > > index 61deab0b5a5a..321fd6f440e6 100644 > > --- a/block/blk-mq-tag.h > > +++ b/block/blk-mq-tag.h > > @@ -35,6 +35,8 @@ extern int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx, > > extern void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool); > > void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, > > void *priv); > > +void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, > > + busy_tag_iter_fn *fn, void *priv); > > static inline struct sbq_wait_state *bt_wait_ptr(struct sbitmap_queue *bt, > > struct blk_mq_hw_ctx *hctx) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > > index e5ef40c603ca..028c5d78e409 100644 > > --- a/block/blk-mq.c > > +++ b/block/blk-mq.c > > @@ -2205,6 +2205,64 @@ int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags, > > return -ENOMEM; > > } > > +static bool blk_mq_count_inflight_rq(struct request *rq, void *data, > > + bool reserved) > > +{ > > + unsigned *count = data; > > + > > + if ((blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT)) > > + (*count)++; > > + > > + return true; > > +} > > + > > +unsigned blk_mq_tags_inflight_rqs(struct blk_mq_tags *tags) > > +{ > > + unsigned count = 0; > > + > > + blk_mq_all_tag_busy_iter(tags, blk_mq_count_inflight_rq, &count); > > + > > + return count; > > +} > > + > > +static void blk_mq_drain_inflight_rqs(struct blk_mq_hw_ctx *hctx) > > +{ > > + while (1) { > > + if (!blk_mq_tags_inflight_rqs(hctx->tags)) > > + break; > > + msleep(5); > > + } > > +} > > + > > +static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node) > > +{ > > + struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node, > > + struct blk_mq_hw_ctx, cpuhp_online); > > + unsigned prev_cpu = -1; > > + > > + if (hctx->flags & BLK_MQ_F_NO_MANAGED_IRQ) > > + return 0; > > is it possible to make this check at registration, such that we don't even > register for when (hctx->flags & BLK_MQ_F_NO_MANAGED_IRQ)? Yeah, good idea, it can be done in that way. > > > + > > + while (true) { > > + unsigned other_cpu = cpumask_next_and(prev_cpu, hctx->cpumask, > > nit: to me name next_cpu seems better OK. > > > + cpu_online_mask); > > + > > + if (other_cpu >= nr_cpu_ids) > > + break; > > + > > + /* return if there is other online CPU on this hctx */ > > + if (other_cpu != cpu) > > + return 0; > > + > > + prev_cpu = other_cpu; > > + } > > + > > + set_bit(BLK_MQ_S_INTERNAL_STOPPED, &hctx->state); > > + blk_mq_drain_inflight_rqs(hctx); > > + > > + 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 > > @@ -2221,6 +2279,9 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node) > > ctx = __blk_mq_get_ctx(hctx->queue, cpu); > > type = hctx->type; > > + if (test_bit(BLK_MQ_S_INTERNAL_STOPPED, &hctx->state)) > > + clear_bit(BLK_MQ_S_INTERNAL_STOPPED, &hctx->state); > > can you just always clear the bit without the test? Yeah. > > > + > > spin_lock(&ctx->lock); > > if (!list_empty(&ctx->rq_lists[type])) { > > list_splice_init(&ctx->rq_lists[type], &tmp); > > @@ -2243,6 +2304,8 @@ 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_AP_BLK_MQ_ONLINE, > > + &hctx->cpuhp_online); > > } > > /* hctx->ctxs will be freed in queue's release handler */ > > @@ -2301,6 +2364,8 @@ static int blk_mq_init_hctx(struct request_queue *q, > > hctx->queue_num = hctx_idx; > > cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead); > > + cpuhp_state_add_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE, > > + &hctx->cpuhp_online); > > hctx->tags = set->tags[hctx_idx]; > > @@ -3536,6 +3601,8 @@ 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_multi(CPUHP_AP_BLK_MQ_ONLINE, "block/mq:online", > > + NULL, blk_mq_hctx_notify_online); > > return 0; > > } > > subsys_initcall(blk_mq_init); > > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h > > index 911cdc6479dc..dc86bdac08f4 100644 > > --- a/include/linux/blk-mq.h > > +++ b/include/linux/blk-mq.h > > @@ -59,6 +59,7 @@ struct blk_mq_hw_ctx { > > atomic_t nr_active; > > struct hlist_node cpuhp_dead; > > + struct hlist_node cpuhp_online; > > I'd reorder with cpuhp_dead Fine. thanks, Ming
