From 2274b029f640cd652ab59c363e5beebf5f50e609 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 15 Feb 2012 09:45:52 +0100 Subject: [PATCH] block: simplify ioc_release_fn() Reverse double lock dancing in ioc_release_fn() can be simplified by just using trylock on the queue_lock and back out from ioc lock on trylock failure. Simplify it. Signed-off-by: Tejun Heo Tested-by: Shaohua Li Signed-off-by: Jens Axboe --- block/blk-ioc.c | 44 +++++++++----------------------------------- 1 file changed, 9 insertions(+), 35 deletions(-) diff --git a/block/blk-ioc.c b/block/blk-ioc.c index 811879c752e4..f53c80ecaf07 100644 --- a/block/blk-ioc.c +++ b/block/blk-ioc.c @@ -79,7 +79,6 @@ static void ioc_release_fn(struct work_struct *work) { struct io_context *ioc = container_of(work, struct io_context, release_work); - struct request_queue *last_q = NULL; unsigned long flags; /* @@ -93,44 +92,19 @@ static void ioc_release_fn(struct work_struct *work) while (!hlist_empty(&ioc->icq_list)) { struct io_cq *icq = hlist_entry(ioc->icq_list.first, struct io_cq, ioc_node); - struct request_queue *this_q = icq->q; + struct request_queue *q = icq->q; - if (this_q != last_q) { - /* - * Need to switch to @this_q. Once we release - * @ioc->lock, it can go away along with @cic. - * Hold on to it. - */ - __blk_get_queue(this_q); - - /* - * blk_put_queue() might sleep thanks to kobject - * idiocy. Always release both locks, put and - * restart. - */ - if (last_q) { - spin_unlock(last_q->queue_lock); - spin_unlock_irqrestore(&ioc->lock, flags); - blk_put_queue(last_q); - } else { - spin_unlock_irqrestore(&ioc->lock, flags); - } - - last_q = this_q; - spin_lock_irqsave(this_q->queue_lock, flags); - spin_lock_nested(&ioc->lock, 1); - continue; + if (spin_trylock(q->queue_lock)) { + ioc_exit_icq(icq); + spin_unlock(q->queue_lock); + } else { + spin_unlock_irqrestore(&ioc->lock, flags); + cpu_relax(); + spin_lock_irqsave_nested(&ioc->lock, flags, 1); } - ioc_exit_icq(icq); } - if (last_q) { - spin_unlock(last_q->queue_lock); - spin_unlock_irqrestore(&ioc->lock, flags); - blk_put_queue(last_q); - } else { - spin_unlock_irqrestore(&ioc->lock, flags); - } + spin_unlock_irqrestore(&ioc->lock, flags); kmem_cache_free(iocontext_cachep, ioc); }