linux-kernel - Re: [PATCH 2/2] S390 topology: don't use kthread() for arch_reinit_sched

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Message-ID: <20080630134537.GC7686@osiris.boeblingen.de.ibm.com>
Date:	Mon, 30 Jun 2008 15:45:37 +0200
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Gautham R Shenoy <ego@...ibm.com>,
	Max Krasnyansky <maxk@...lcomm.com>, Paul Jackson <pj@....com>,
	Paul Menage <menage@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Vegard Nossum <vegard.nossum@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] S390 topology: don't use kthread() for
	arch_reinit_sched_domains()

On Sun, Jun 29, 2008 at 08:51:32PM +0400, Oleg Nesterov wrote:
> Untested, needs Heiko's ack.
> 
> Now that it is safe to use get_online_cpus() we can revert
> 
> 	[S390] cpu topology: Fix possible deadlock.
> 	commit: fd781fa25c9e9c6fd1599df060b05e7c4ad724e5
> 
> and call arch_reinit_sched_domains() directly from topology_work_fn().
> 
> Signed-off-by: Oleg Nesterov <oleg@...sign.ru>
> 
> --- 26-rc2/arch/s390/kernel/topology.c~WQ_5_TOPOLOGY	2008-05-18 15:43:28.000000000 +0400
> +++ 26-rc2/arch/s390/kernel/topology.c	2008-06-29 20:42:38.000000000 +0400
> @@ -9,7 +9,6 @@
>  #include <linux/device.h>
>  #include <linux/bootmem.h>
>  #include <linux/sched.h>
> -#include <linux/kthread.h>
>  #include <linux/workqueue.h>
>  #include <linux/cpu.h>
>  #include <linux/smp.h>
> @@ -230,20 +229,9 @@ void arch_update_cpu_topology(void)
>  	}
>  }
> 
> -static int topology_kthread(void *data)
> -{
> -	arch_reinit_sched_domains();
> -	return 0;
> -}
> -
>  static void topology_work_fn(struct work_struct *work)
>  {
> -	/* We can't call arch_reinit_sched_domains() from a multi-threaded
> -	 * workqueue context since it may deadlock in case of cpu hotplug.
> -	 * So we have to create a kernel thread in order to call
> -	 * arch_reinit_sched_domains().
> -	 */
> -	kthread_run(topology_kthread, NULL, "topology_update");
> +	arch_reinit_sched_domains();

Thank you! Tested and still works ;)

Acked-by: Heiko Carstens <heiko.carstens@...ibm.com>
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