From bccb5f7c8bdfe460d95f986c6edf2e75d8052897 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 4 Apr 2014 21:34:48 -0600 Subject: [PATCH] blk-mq: fix potential stall during CPU unplug with IO pending When a CPU is unplugged, we move the blk_mq_ctx request entries to the current queue. The current code forgets to remap the blk_mq_hw_ctx before marking the software context pending, which breaks if old-cpu and new-cpu don't map to the same hardware queue. Additionally, if we mark entries as pending in the new hardware queue, then make sure we schedule it for running. Otherwise request could be sitting there until someone else queues IO for that hardware queue. Signed-off-by: Jens Axboe --- block/blk-mq.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index b1bcc619d0ea..1d2a9bdbee57 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -956,6 +956,7 @@ static void blk_mq_hctx_notify(void *data, unsigned long action, unsigned int cpu) { struct blk_mq_hw_ctx *hctx = data; + struct request_queue *q = hctx->queue; struct blk_mq_ctx *ctx; LIST_HEAD(tmp); @@ -965,7 +966,7 @@ static void blk_mq_hctx_notify(void *data, unsigned long action, /* * Move ctx entries to new CPU, if this one is going away. */ - ctx = __blk_mq_get_ctx(hctx->queue, cpu); + ctx = __blk_mq_get_ctx(q, cpu); spin_lock(&ctx->lock); if (!list_empty(&ctx->rq_list)) { @@ -977,7 +978,7 @@ static void blk_mq_hctx_notify(void *data, unsigned long action, if (list_empty(&tmp)) return; - ctx = blk_mq_get_ctx(hctx->queue); + ctx = blk_mq_get_ctx(q); spin_lock(&ctx->lock); while (!list_empty(&tmp)) { @@ -988,10 +989,13 @@ static void blk_mq_hctx_notify(void *data, unsigned long action, list_move_tail(&rq->queuelist, &ctx->rq_list); } + hctx = q->mq_ops->map_queue(q, ctx->cpu); blk_mq_hctx_mark_pending(hctx, ctx); spin_unlock(&ctx->lock); blk_mq_put_ctx(ctx); + + blk_mq_run_hw_queue(hctx, true); } static int blk_mq_init_hw_commands(struct blk_mq_hw_ctx *hctx,