linux-kernel - [PATCH] Xen: Fix warning when hot-unplugging virtual block devices

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Message-ID: <48AD5373.201@citrix.com>
Date:	Thu, 21 Aug 2008 12:37:23 +0100
From:	Alex Nixon <alex.nixon@...rix.com>
To:	Jeremy Fitzhardinge <Jeremy.Fitzhardinge@...rix.com>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] Xen: Fix warning when hot-unplugging virtual block devices

From: Alex Nixon <alex.nixon@...rix.com>
Date: Thu, 21 Aug 2008 12:30:54 +0100
Subject: [PATCH] Xen: Fix warning when hot-unplugging virtual block devices

WARNING: at kernel/softirq.c:136 local_bh_enable+0x3f/0x8a()

del_gendisk needs IRQs enabled, as the code path eventually reaches local_bh_enable.
blk_stop_queue needs them disabled - so do so temporarily.

It shouldn't matter if an interrupt comes in whilst blkif_io_lock is held, as it will block on the lock.  Upon acquisition, it'll realise the device is down and exit cleanly.

Signed-off-by: Alex Nixon <alex.nixon@...rix.com>
---
 drivers/block/xen-blkfront.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index d5e7532..95cee2c 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -899,16 +899,18 @@ static void blkfront_closing(struct xenbus_device *dev)
 	if (info->rq == NULL)
 		goto out;
 
-	spin_lock_irqsave(&blkif_io_lock, flags);
+	spin_lock(&blkif_io_lock);
 
 	del_gendisk(info->gd);
 
+	local_irq_save(flags);
 	/* No more blkif_request(). */
 	blk_stop_queue(info->rq);
+	local_irq_restore(flags);
 
 	/* No more gnttab callback work. */
 	gnttab_cancel_free_callback(&info->callback);
-	spin_unlock_irqrestore(&blkif_io_lock, flags);
+	spin_unlock(&blkif_io_lock);
 
 	/* Flush gnttab callback work. Must be done with no locks held. */
 	flush_scheduled_work();
-- 
1.5.4.3

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