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Date: Thu, 22 Jun 2006 18:48:50 -0700
From: Andrew Morton <akpm@osdl.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu
Subject: Re: [patch 1/3] Drop tasklist lock in do_sched_setscheduler
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On Thu, 22 Jun 2006 09:08:38 -0000
Thomas Gleixner <tglx@linutronix.de> wrote:

> 
> There is no need to hold tasklist_lock across the setscheduler call, when we
> pin the task structure with get_task_struct(). Interrupts are disabled in 
> setscheduler anyway and the permission checks do not need interrupts disabled.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
> 
>  kernel/sched.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> Index: linux-2.6.17-mm/kernel/sched.c
> ===================================================================
> --- linux-2.6.17-mm.orig/kernel/sched.c	2006-06-22 10:26:11.000000000 +0200
> +++ linux-2.6.17-mm/kernel/sched.c	2006-06-22 10:26:11.000000000 +0200
> @@ -4140,8 +4140,10 @@
>  		read_unlock_irq(&tasklist_lock);
>  		return -ESRCH;
>  	}
> -	retval = sched_setscheduler(p, policy, &lparam);
> +	get_task_struct(p);
>  	read_unlock_irq(&tasklist_lock);
> +	retval = sched_setscheduler(p, policy, &lparam);
> +	put_task_struct(p);
>  	return retval;
>  }
>  

Is this optimisation actually related to the rt-mutex patches, or to the
other two patches?