aoe: manipulate aoedev network stats under lock
Ed Cashin [Tue, 18 Dec 2012 00:03:47 +0000 (16:03 -0800)]
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@coraid.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/block/aoe/aoecmd.c

index 6ea27fd..9aefbe3 100644 (file)
@@ -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;