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authorTejun Heo <tj@kernel.org>2012-02-11 12:37:25 +0100
committerJens Axboe <axboe@kernel.dk>2012-02-11 12:37:25 +0100
commitd8c66c5d59247e25a69428aced0b79d33b9c66d6 (patch)
tree1aed7dc560df36157d8cde6fdebc1d86f4ed61ad /block
parentf6302f1bcd75a042df69866d98b8d775a668f8f1 (diff)
downloadlinux-linaro-stable-d8c66c5d59247e25a69428aced0b79d33b9c66d6.tar.gz
block: fix lockdep warning on io_context release put_io_context()
11a3122f6c "block: strip out locking optimization in put_io_context()" removed ioc_lock depth lockdep annoation along with locking optimization; however, while recursing from put_io_context() is no longer possible, ioc_release_fn() may still end up putting the last reference of another ioc through elevator, which wlil grab ioc->lock triggering spurious (as the ioc is always different one) A-A deadlock warning. As this can only happen one time from ioc_release_fn(), using non-zero subclass from ioc_release_fn() is enough. Use subclass 1. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/blk-ioc.c21
1 files changed, 14 insertions, 7 deletions
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index 9884fd7427fe..8b782a63c297 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -80,8 +80,15 @@ 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;
- spin_lock_irq(&ioc->lock);
+ /*
+ * Exiting icq may call into put_io_context() through elevator
+ * which will trigger lockdep warning. The ioc's are guaranteed to
+ * be different, use a different locking subclass here. Use
+ * irqsave variant as there's no spin_lock_irq_nested().
+ */
+ spin_lock_irqsave_nested(&ioc->lock, flags, 1);
while (!hlist_empty(&ioc->icq_list)) {
struct io_cq *icq = hlist_entry(ioc->icq_list.first,
@@ -103,15 +110,15 @@ static void ioc_release_fn(struct work_struct *work)
*/
if (last_q) {
spin_unlock(last_q->queue_lock);
- spin_unlock_irq(&ioc->lock);
+ spin_unlock_irqrestore(&ioc->lock, flags);
blk_put_queue(last_q);
} else {
- spin_unlock_irq(&ioc->lock);
+ spin_unlock_irqrestore(&ioc->lock, flags);
}
last_q = this_q;
- spin_lock_irq(this_q->queue_lock);
- spin_lock(&ioc->lock);
+ spin_lock_irqsave(this_q->queue_lock, flags);
+ spin_lock_nested(&ioc->lock, 1);
continue;
}
ioc_exit_icq(icq);
@@ -119,10 +126,10 @@ static void ioc_release_fn(struct work_struct *work)
if (last_q) {
spin_unlock(last_q->queue_lock);
- spin_unlock_irq(&ioc->lock);
+ spin_unlock_irqrestore(&ioc->lock, flags);
blk_put_queue(last_q);
} else {
- spin_unlock_irq(&ioc->lock);
+ spin_unlock_irqrestore(&ioc->lock, flags);
}
kmem_cache_free(iocontext_cachep, ioc);