netdev - Re: [PATCH v2] bonding: Fix jiffies overflow problems (again)

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Message-Id: <20100906.131647.115921981.davem@davemloft.net>
Date:	Mon, 06 Sep 2010 13:16:47 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	jdelvare@...e.de
Cc:	eric.dumazet@...il.com, fubar@...ibm.com,
	bonding-devel@...ts.sourceforge.net, netdev@...r.kernel.org,
	jbohac@...e.cz
Subject: Re: [PATCH v2] bonding: Fix jiffies overflow problems (again)

From: Jean Delvare <jdelvare@...e.de>
Date: Thu, 2 Sep 2010 17:45:54 +0200

> From: Jiri Bohac <jbohac@...e.cz>
> 
> The time_before_eq()/time_after_eq() functions operate on unsigned
> long and only work if the difference between the two compared values
> is smaller than half the range of unsigned long (31 bits on i386).
> 
> Some of the variables (slave->jiffies, dev->trans_start, dev->last_rx)
> used by bonding store a copy of jiffies and may not be updated for a
> long time. With HZ=1000, time_before_eq()/time_after_eq() will start
> giving bad results after ~25 days.
> 
> jiffies will never be before slave->jiffies, dev->trans_start,
> dev->last_rx by more than possibly a couple ticks caused by preemption
> of this code. This allows us to detect/prevent these overflows by
> replacing time_before_eq()/time_after_eq() with time_in_range().
> 
> Signed-off-by: Jiri Bohac <jbohac@...e.cz>
> Signed-off-by: Jean Delvare <jdelvare@...e.de>

Applied, thanks.
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