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Date: Mon, 20 Apr 2015 20:36:45 +0200 From: Dongsu Park <dongsu.park@...fitbricks.com> To: Ming Lei <ming.lei@...onical.com> Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@...radead.org> Subject: Re: panic with CPU hotplug + blk-mq + scsi-mq On 21.04.2015 00:48, Ming Lei wrote: > Thanks for providing that. > The trick is just in CPU number and virito-scsi hw queue number, > and that is why I asked that, :-) > Now the problem is quite clear, before CPU1 online, suppose > CPU3 is mapped hw queue 6, and CPU 3 will map to hw queue 5 > after CPU1 is offline, unfortunately current code can't allocate > tags for hw queue 5 even it becomes mapped. > The following updated patch(include original patch 2) will fix > the problem, and patch 1 is required too. > So the following patch should fix your hotplug issue. Yes, it works indeed. Thanks a lot! :-) You can add: Tested-by: Dongsu Park <dongsu.park@...fitbricks.com> As the original patch didn't apply, I had to change some nitpicks though. (see below) Cheers, Dongsu ---- >From 8c0edcbbdfbab67dc8ae2fd46cca6a86e0cadcba Mon Sep 17 00:00:00 2001 From: Ming Lei <ming.lei@...onical.com> Date: Sun, 19 Apr 2015 23:32:46 +0800 Subject: [PATCH v1 2/2] blk-mq: fix CPU hotplug handling Firstly the hctx->tags have to be set as NULL if it is to be disabled no matter if set->tags[i] is NULL or not in blk_mq_map_swqueue() because shared tags can be freed already from another request queue. The same situation has to be considered in blk_mq_hctx_cpu_online() too. Finally one unmapped hw queue can be remapped after CPU topo is changed, we need to allocate tags for the hw queue in blk_mq_map_swqueue() too. Then tags allocation for hw queue can be removed in hctx cpu online notifier, and it is reasonable to do that after remapping is done. Cc: <stable@...r.kernel.org> Reported-by: Dongsu Park <dongsu.park@...fitbricks.com> Signed-off-by: Ming Lei <ming.lei@...onical.com> --- block/blk-mq.c | 34 +++++++++++++--------------------- 1 file changed, 13 insertions(+), 21 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 078840ce8670..df4b9597e477 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1573,22 +1573,6 @@ static int blk_mq_hctx_cpu_offline(struct blk_mq_hw_ctx *hctx, int cpu) return NOTIFY_OK; } -static int blk_mq_hctx_cpu_online(struct blk_mq_hw_ctx *hctx, int cpu) -{ - struct request_queue *q = hctx->queue; - struct blk_mq_tag_set *set = q->tag_set; - - if (set->tags[hctx->queue_num]) - return NOTIFY_OK; - - set->tags[hctx->queue_num] = blk_mq_init_rq_map(set, hctx->queue_num); - if (!set->tags[hctx->queue_num]) - return NOTIFY_STOP; - - hctx->tags = set->tags[hctx->queue_num]; - return NOTIFY_OK; -} - static int blk_mq_hctx_notify(void *data, unsigned long action, unsigned int cpu) { @@ -1596,8 +1580,11 @@ static int blk_mq_hctx_notify(void *data, unsigned long action, if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) return blk_mq_hctx_cpu_offline(hctx, cpu); - else if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) - return blk_mq_hctx_cpu_online(hctx, cpu); + + /* + * In case of CPU online, tags will be reallocated + * after new mapping is done in blk_mq_map_swqueue(). + */ return NOTIFY_OK; } @@ -1779,6 +1766,7 @@ static void blk_mq_map_swqueue(struct request_queue *q) unsigned int i; struct blk_mq_hw_ctx *hctx; struct blk_mq_ctx *ctx; + struct blk_mq_tag_set *set = q->tag_set; queue_for_each_hw_ctx(q, hctx, i) { cpumask_clear(hctx->cpumask); @@ -1805,16 +1793,20 @@ static void blk_mq_map_swqueue(struct request_queue *q) * disable it and free the request entries. */ if (!hctx->nr_ctx) { - struct blk_mq_tag_set *set = q->tag_set; - if (set->tags[i]) { blk_mq_free_rq_map(set, set->tags[i], i); set->tags[i] = NULL; - hctx->tags = NULL; } + hctx->tags = NULL; continue; } + /* unmapped hw queue can be remapped after CPU topo changed */ + if (!set->tags[i]) + set->tags[i] = blk_mq_init_rq_map(set, hctx->queue_num); + hctx->tags = set->tags[i]; + WARN_ON(!hctx->tags); + /* * Initialize batch roundrobin counts */ -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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