From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 21 Oct 2008 18:17:35 +0000 (+0200)
Subject: NOHZ: fix thinko in the timer restart code path
X-Git-Tag: v2.6.28-rc1~38^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c4bd822e7b12a9008241d76db45b665f2fef180c;p=pandora-kernel.git

NOHZ: fix thinko in the timer restart code path

commit fb02fbc14d17837b4b7b02dbb36142c16a7bf208 (NOHZ: restart tick
device from irq_enter())

solves the problem of stale jiffies when long running softirqs happen
in a long idle sleep period, but it has a major thinko in it:

When the interrupt which came in _is_ the timer interrupt which should
expire ts->sched_timer then we cancel and rearm the timer _before_ it
gets expired in hrtimer_interrupt() to the next period. That means the
call back function is not called. This game can go on for ever :(

Prevent this by making sure to only rearm the timer when the expiry
time is more than one tick_period away. Otherwise keep it running as
it is either already expired or will expiry at the right point to
update jiffies.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Venkatesch Pallipadi <venkatesh.pallipadi@intel.com>
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