diff mbox

[v5,07/12] block: Add a comment above queue_lockdep_assert_held()

Message ID 20170620181549.24903-8-bart.vanassche@wdc.com (mailing list archive)
State New, archived
Headers show

Commit Message

Bart Van Assche June 20, 2017, 6:15 p.m. UTC 
From: Bart Van Assche <bart.vanassche@sandisk.com>

Add a comment above the queue_lockdep_assert_held() macro that
explains the purpose of the q->queue_lock test.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Ming Lei <ming.lei@redhat.com>
---
 include/linux/blkdev.h | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

Hannes Reinecke June 21, 2017, 6:55 a.m. UTC | #1 
On 06/20/2017 08:15 PM, Bart Van Assche wrote:
> From: Bart Van Assche <bart.vanassche@sandisk.com>
> 
> Add a comment above the queue_lockdep_assert_held() macro that
> explains the purpose of the q->queue_lock test.
> 
> Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Cc: Hannes Reinecke <hare@suse.com>
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Ming Lei <ming.lei@redhat.com>
> ---
>  include/linux/blkdev.h | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index ff0ae83235ea..c00a6b99e77c 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -635,6 +635,13 @@ struct request_queue {
>  				 (1 << QUEUE_FLAG_SAME_COMP)	|	\
>  				 (1 << QUEUE_FLAG_POLL))
>  
> +/*
> + * @q->queue_lock is set while a queue is being initialized. Since we know
> + * that no other threads access the queue object before @q->queue_lock has
> + * been set, it is safe to manipulate queue flags without holding the
> + * queue_lock if @q->queue_lock == NULL. See also blk_alloc_queue_node() and
> + * blk_init_allocated_queue().
> + */
>  static inline void queue_lockdep_assert_held(struct request_queue *q)
>  {
>  	if (q->queue_lock)
> 
Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes
diff mbox

Patch

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index ff0ae83235ea..c00a6b99e77c 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -635,6 +635,13 @@  struct request_queue {
 				 (1 << QUEUE_FLAG_SAME_COMP)	|	\
 				 (1 << QUEUE_FLAG_POLL))
 
+/*
+ * @q->queue_lock is set while a queue is being initialized. Since we know
+ * that no other threads access the queue object before @q->queue_lock has
+ * been set, it is safe to manipulate queue flags without holding the
+ * queue_lock if @q->queue_lock == NULL. See also blk_alloc_queue_node() and
+ * blk_init_allocated_queue().
+ */
 static inline void queue_lockdep_assert_held(struct request_queue *q)
 {
 	if (q->queue_lock)