linux-kernel - 100% iowait on one of cpus in current -git

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Date:	Mon, 22 Oct 2007 08:22:52 +0200
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: 100% iowait on one of cpus in current -git

Hi,

I found a bug in current -git:

On my system on of cpus stays 100% in iowait mode (I have core 2 duo)
Otherwise the system works OK, no disk activity and/or slowdown.
Suspecting that this is a swap-related problem I tried to turn swap of, but it doesn't affect anything.
It is probably some accounting bug.

If I start with init=/bin/bash, then this disappears.
I tried then to start usual /etc/init.d scripts then, and first one to show this bug was gpm.
but then I rebooted the system to X without gpm, and I still see 100% iowait.

No additional messages in dmesg.

I tried to bisect this, but eventually I run into other bugs that cause system to oops early.

This is very rough estimate of the bug location:

HEAD
......
c8f30ae54714abf494d79826d90b5e4844fbf355 - has the above bug, but otherwise works properly
.....
5c8e191e8437616a498a8e1cc0af3dd0d32bbff2 - fails early
.....
f4a1c2bce002f683801bcdbbc9fd89804614fb6b - last known working revision

Best regards,
	Maxim Levitsky

PS: .config attached.

View attachment ".config" of type "text/plain" (48533 bytes)