linux-kernel - Re: [PATCH]: Fix bogus softlockup warning with sysrq-t

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Message-ID: <460955CC.70006@redhat.com>
Date:	Tue, 27 Mar 2007 13:35:08 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	clalance@...hat.com, mingo@...hat.com, davej@...hat.com,
	Thilo.Cestonaro.external@...itsu-siemens.com
Subject: Re: [PATCH]: Fix bogus softlockup warning with sysrq-t



Jeremy Fitzhardinge wrote:
>
> diff -r 4c81d8cafb67 drivers/char/sysrq.c
> --- a/drivers/char/sysrq.c	Tue Mar 27 01:16:07 2007 -0700
> +++ b/drivers/char/sysrq.c	Tue Mar 27 01:18:05 2007 -0700
> @@ -408,6 +408,8 @@ void __handle_sysrq(int key, struct tty_
>  	int i;
>  	unsigned long flags;
>  
> +	softlockup_global_disable();
> +
>  	spin_lock_irqsave(&sysrq_key_table_lock, flags);
>  	orig_log_level = console_loglevel;
>  	console_loglevel = 7;
> @@ -445,6 +447,8 @@ void __handle_sysrq(int key, struct tty_
>  		console_loglevel = orig_log_level;
>  	}
>  	spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
> +
> +	softlockup_global_enable();
>  }
>  
>   

I wonder if that's too strong of a fix.  It's only the sysrq-t case that 
is the problem.  AFAIK, none of the other sysrq-t operations hold the 
tasklist_lock for a long time.  I'd move these around show_state.

P.
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