linux-kernel - Re: [PATCH 5/16] fix-kthread-niceness.diff

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Message-Id: <20070401223935.f73402a8.akpm@linux-foundation.org>
Date:	Sun, 1 Apr 2007 22:39:35 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Chris Wright <chrisw@...s-sol.org>
Subject: Re: [PATCH 5/16] fix-kthread-niceness.diff

On Sun, 1 Apr 2007 20:14:40 +0200 (MEST) Jan Engelhardt <jengelh@...ux01.gwdg.de> wrote:

> Fix kevent's childs priority greedy-ness. Such tasks were always scheduled
> at nice level -5 and, at that time, udev stole us the CPU time with -5.
> 
> Already posted at http://lkml.org/lkml/2005/1/10/85
> 
> Signed-off-by: Jan Engelhardt <jengelh@....de>
> Cc: Chris Wright <chrisw@...s-sol.org>
> 
>  kmod.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> Index: linux-2.6.21-rc5/kernel/kmod.c
> ===================================================================
> --- linux-2.6.21-rc5.orig/kernel/kmod.c
> +++ linux-2.6.21-rc5/kernel/kmod.c
> @@ -165,6 +165,7 @@ static int ____call_usermodehelper(void 
>  
>  	/* We can run anywhere, unlike our parent keventd(). */
>  	set_cpus_allowed(current, CPU_MASK_ALL);
> +	set_user_nice(current, 0);
>  
>  	retval = -EPERM;
>  	if (current->fs->root)
> #<EOF>

-ETOOOBSCURE.

--- a/kernel/kmod.c~fix-kthread-nicenessdiff-fix
+++ a/kernel/kmod.c
@@ -163,6 +163,11 @@ static int ____call_usermodehelper(void 
 
 	/* We can run anywhere, unlike our parent keventd(). */
 	set_cpus_allowed(current, CPU_MASK_ALL);
+
+	/*
+	 * Our parent is keventd, which runs with elevated scheduling priority.
+	 * Avoid propagating that into the userspace child.
+	 */
 	set_user_nice(current, 0);
 
 	retval = -EPERM;
_

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