linux-kernel - [PATCH 5/8] aoe: manipulate aoedev network stats under lock

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Message-Id: <e8a1a14896156327aea0feff6a1076f7f121b748.1352410985.git.ecashin@coraid.com>
Date:	Thu, 8 Nov 2012 19:25:17 -0500
From:	Ed Cashin <ecashin@...aid.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, ecashin@...aid.com
Subject:  [PATCH 5/8] aoe: manipulate aoedev network stats under lock

With this bugfix in place the calculation of the criterion for
"lateness" is performed under lock.  Without the lock, there is a
chance that one of the non-atomic operations performed on the
round trip time statistics could be incomplete, such that an
incorrect lateness criterion would be calculated.

Without this change, the effect of the bug would be rare
unecessary but benign retransmissions.

Signed-off-by: Ed Cashin <ecashin@...aid.com>
---
 drivers/block/aoe/aoecmd.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
index 6ea27fd..9aefbe3 100644
--- a/drivers/block/aoe/aoecmd.c
+++ b/drivers/block/aoe/aoecmd.c
@@ -603,14 +603,14 @@ rexmit_timer(ulong vp)
 
 	d = (struct aoedev *) vp;
 
+	spin_lock_irqsave(&d->lock, flags);
+
 	/* timeout based on observed timings and variations */
 	timeout = 2 * d->rttavg >> RTTSCALE;
 	timeout += 8 * d->rttdev >> RTTDSCALE;
 	if (timeout == 0)
 		timeout = 1;
 
-	spin_lock_irqsave(&d->lock, flags);
-
 	if (d->flags & DEVFL_TKILL) {
 		spin_unlock_irqrestore(&d->lock, flags);
 		return;
-- 
1.7.1

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