linux-kernel - [PATCH 3.16 039/133] block: Relax a check in blk_start

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Message-ID: <lsq.1511315892.34521770@decadent.org.uk>
Date:   Wed, 22 Nov 2017 01:58:12 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Johannes Thumshirn" <jthumshirn@...e.de>,
        "Christoph Hellwig" <hch@....de>, "Jens Axboe" <axboe@...nel.dk>,
        "Bart Van Assche" <bart.vanassche@....com>,
        "Hannes Reinecke" <hare@...e.de>, "Andrew Morton" <akpm@...l.org>,
        "Paolo 'Blaisorblade' Giarrusso" <blaisorblade@...oo.it>
Subject: [PATCH 3.16 039/133] block: Relax a check in blk_start_queue()

3.16.51-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Bart Van Assche <bart.vanassche@....com>

commit 4ddd56b003f251091a67c15ae3fe4a5c5c5e390a upstream.

Calling blk_start_queue() from interrupt context with the queue
lock held and without disabling IRQs, as the skd driver does, is
safe. This patch avoids that loading the skd driver triggers the
following warning:

WARNING: CPU: 11 PID: 1348 at block/blk-core.c:283 blk_start_queue+0x84/0xa0
RIP: 0010:blk_start_queue+0x84/0xa0
Call Trace:
 skd_unquiesce_dev+0x12a/0x1d0 [skd]
 skd_complete_internal+0x1e7/0x5a0 [skd]
 skd_complete_other+0xc2/0xd0 [skd]
 skd_isr_completion_posted.isra.30+0x2a5/0x470 [skd]
 skd_isr+0x14f/0x180 [skd]
 irq_forced_thread_fn+0x2a/0x70
 irq_thread+0x144/0x1a0
 kthread+0x125/0x140
 ret_from_fork+0x2a/0x40

Fixes: commit a038e2536472 ("[PATCH] blk_start_queue() must be called with irq disabled - add warning")
Signed-off-by: Bart Van Assche <bart.vanassche@....com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@...oo.it>
Cc: Andrew Morton <akpm@...l.org>
Cc: Christoph Hellwig <hch@....de>
Cc: Hannes Reinecke <hare@...e.de>
Cc: Johannes Thumshirn <jthumshirn@...e.de>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 block/blk-core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -198,7 +198,7 @@ EXPORT_SYMBOL(blk_delay_queue);
  **/
 void blk_start_queue(struct request_queue *q)
 {
-	WARN_ON(!irqs_disabled());
+	WARN_ON(!in_interrupt() && !irqs_disabled());
 
 	queue_flag_clear(QUEUE_FLAG_STOPPED, q);
 	__blk_run_queue(q);