Regression (bisected): Lots of wakeups when using battery

From: Jaime Velasco Juan
Date: Fri Jul 30 2010 - 17:45:52 EST

Hi, testing 2.6.35-rc5 I noticed that when my laptop is on battery,
there are bursts of wakeups (they seem random, but usually happens once
each 5 sec. or so; they cause some audible noise). If the laptop is plugged
it behaves well. In single user mode, there are usually 2 wakeups/sec with
the system idle, but on battery an with the bug, it goes to more than 100 w/s.

Bisection points to:

commit 3310d4d38fbc514e7b18bd3b1eea8effdd63b5aa
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Thu Jun 17 18:02:37 2010 +0200

nohz: Fix nohz ratelimit

Chris Wedgwood reports that 39c0cbe (sched: Rate-limit nohz) causes a
serial console regression, unresponsiveness, and indeed it does. The
reason is that the nohz code is skipped even when the tick was already
stopped before the nohz_ratelimit(cpu) condition changed.

Move the nohz_ratelimit() check to the other conditions which prevent
long idle sleeps.

Reverting said commit seems to fix the issue.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at