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block: mq: use cpu_light() 

there is a might sleep splat because get_cpu() disables preemption and
later we grab a lock. As a workaround for this we use get_cpu_light()
and an additional lock to prevent taking the same ctx.

There is a lock member in the ctx already but there some functions which do ++
on the member and this works with irq off but on RT we would need the extra lock.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
This commit is contained in:
Sebastian Andrzej Siewior 2014-04-09 10:37:23 +02:00 committed by Alibek Omarov
parent cc5d4c7047
commit 2d535af0db
2 changed files with 18 additions and 3 deletions
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20
block/blk-mq.c
View File

@ -30,7 +30,11 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx);
static struct blk_mq_ctx *__blk_mq_get_ctx(struct request_queue *q,
unsigned int cpu)
{
return per_cpu_ptr(q->queue_ctx, cpu);
struct blk_mq_ctx *ctx;
ctx = per_cpu_ptr(q->queue_ctx, cpu);
spin_lock(&ctx->cpu_lock);
return ctx;
}
/*
@ -41,12 +45,18 @@ static struct blk_mq_ctx *__blk_mq_get_ctx(struct request_queue *q,
*/
static struct blk_mq_ctx *blk_mq_get_ctx(struct request_queue *q)
{
return __blk_mq_get_ctx(q, get_cpu());
return __blk_mq_get_ctx(q, get_cpu_light());
}
static void __blk_mq_put_ctx(struct blk_mq_ctx *ctx)
{
spin_unlock(&ctx->cpu_lock);
}
static void blk_mq_put_ctx(struct blk_mq_ctx *ctx)
{
put_cpu();
__blk_mq_put_ctx(ctx);
put_cpu_light();
}
/*
@ -897,7 +907,9 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
if (list_empty(&plug->mq_list))
trace_block_plug(q);
else if (request_count >= BLK_MAX_REQUEST_COUNT) {
spin_unlock(&ctx->cpu_lock);
blk_flush_plug_list(plug, false);
spin_lock(&ctx->cpu_lock);
trace_block_plug(q);
}
list_add_tail(&rq->queuelist, &plug->mq_list);
@ -973,6 +985,7 @@ static void blk_mq_hctx_notify(void *data, unsigned long action,
clear_bit(ctx->index_hw, hctx->ctx_map);
}
spin_unlock(&ctx->lock);
__blk_mq_put_ctx(ctx);
if (list_empty(&tmp))
return;
@ -1212,6 +1225,7 @@ static void blk_mq_init_cpu_queues(struct request_queue *q,
memset(__ctx, 0, sizeof(*__ctx));
__ctx->cpu = i;
spin_lock_init(&__ctx->lock);
spin_lock_init(&__ctx->cpu_lock);
INIT_LIST_HEAD(&__ctx->rq_list);
__ctx->queue = q;

1
block/blk-mq.h
View File

@ -7,6 +7,7 @@ struct blk_mq_ctx {
struct list_head rq_list;
} ____cacheline_aligned_in_smp;
spinlock_t cpu_lock;
unsigned int cpu;
unsigned int index_hw;
unsigned int ipi_redirect;