linux-kernel - Re: [BUG?] false positive in soft lockup detector while unlzma initramfs on slow cpu

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Message-Id: <20130129155917.4ee64214.akpm@linux-foundation.org>
Date:	Tue, 29 Jan 2013 15:59:17 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Mike Lykov <combr@...dex.ru>, Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, linux-watchdog@...r.kernel.org,
	kirill@...temov.name
Subject: Re: [BUG?] false positive in soft lockup detector while unlzma
 initramfs on slow cpu

On Tue, 29 Jan 2013 10:33:48 -0500
Don Zickus <dzickus@...hat.com> wrote:

> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -79,6 +79,14 @@ static int __init softlockup_panic_setup(char *str)
>  }
>  __setup("softlockup_panic=", softlockup_panic_setup);
>  
> +static int __init watchdog_thresh_setup(char *str)
> +{
> +	watchdog_thresh = simple_strtoul(str, NULL, 0);
> +
> +	return 1;
> +}
> +__setup("watchdog_thresh=", watchdog_thresh_setup);

I wonder if there's some magical way in which we can set any sysctl
from the kernel command line.  Add sys.vm.min_free_kbytes=42 to the
command line, walk the hierarchy late in boot...

To address Mike's bug I suggest we poke a touch_softlockup_watchdog()
into the appropriate place.  Presumably the loop in
lib/decompress_unlzma.c:unlzma().  The decompress code makes me cry.
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