Messages in this thread Patch in this message | | | From | Tejun Heo <> | Subject | [PATCH 2/6] block: allow blk_execute_rq_nowait() to be called from IRQ context | Date | Tue, 25 Oct 2011 18:02:03 -0700 |
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Currently blk_execute_rq_nowait() directly calls __blk_run_queue() and thus must be called from sleepable context. This patch updates the function such that it can be called from non-sleepable context and schedules async execution in such cases. This will be used to unexport elv_add_request().
While at it, add FIXME comment for REQ_TYPE_PM_RESUME special case.
-v2: hch pointed out that blk_execute_rq_nowait() can be hot path for some drivers. Retained direct execution from sleepable context.
Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Christoph Hellwig <hch@infradead.org> --- block/blk-exec.c | 29 ++++++++++++++++++++++------- 1 files changed, 22 insertions(+), 7 deletions(-)
diff --git a/block/blk-exec.c b/block/blk-exec.c index a1ebceb..b686f2b 100644 --- a/block/blk-exec.c +++ b/block/blk-exec.c @@ -49,6 +49,8 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk, rq_end_io_fn *done) { int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK; + bool may_sleep = !preempt_count() && !irqs_disabled(); + unsigned long flags; if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) { rq->errors = -ENXIO; @@ -59,14 +61,27 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk, rq->rq_disk = bd_disk; rq->end_io = done; - WARN_ON(irqs_disabled()); - spin_lock_irq(q->queue_lock); + + spin_lock_irqsave(q->queue_lock, flags); __elv_add_request(q, rq, where); - __blk_run_queue(q); - /* the queue is stopped so it won't be run */ - if (rq->cmd_type == REQ_TYPE_PM_RESUME) - q->request_fn(q); - spin_unlock_irq(q->queue_lock); + + /* + * Some drivers beat this path pretty hard. As an optimization, if + * we're being called from sleepable context, run @q directly. + */ + if (may_sleep) { + __blk_run_queue(q); + /* + * The queue is stopped so it won't be run. + * FIXME: Please kill me along with REQ_TYPE_PM_RESUME. + */ + if (rq->cmd_type == REQ_TYPE_PM_RESUME) + q->request_fn(q); + } else { + blk_run_queue_async(q); + } + + spin_unlock_irqrestore(q->queue_lock, flags); } EXPORT_SYMBOL_GPL(blk_execute_rq_nowait); -- 1.7.3.1
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