linux-kernel - Re: [PATCH] sched: fix the wrong mask

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Date:	Fri, 17 Oct 2008 12:58:19 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	miaox@...fujitsu.com, Ingo Molnar <mingo@...e.hu>,
	Linux-Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched: fix the wrong mask_len

On Fri, 2008-10-17 at 12:33 +0200, Peter Zijlstra wrote:
> On Fri, 2008-10-17 at 19:25 +0900, KOSAKI Motohiro wrote:
> > > If the NR_CPUS isn't a multiple of 32, we get a truncated string of sched
> > > domains by catting /proc/schedstat. This is caused by the wrong mask_len.
> > > 
> > > This patch fix it.
> > > 
> > > Signed-off-by: Miao Xie <miaox@...fujitsu.com>
> > > 
> > > ---
> > >  kernel/sched_stats.h |    2 +-
> > >  1 files changed, 1 insertions(+), 1 deletions(-)
> > > 
> > > diff --git a/kernel/sched_stats.h b/kernel/sched_stats.h
> > > index 8385d43..81365b3 100644
> > > --- a/kernel/sched_stats.h
> > > +++ b/kernel/sched_stats.h
> > > @@ -9,7 +9,7 @@
> > >  static int show_schedstat(struct seq_file *seq, void *v)
> > >  {
> > >  	int cpu;
> > > -	int mask_len = NR_CPUS/32 * 9;
> > > +	int mask_len = (NR_CPUS/32 + 1) * 9;
> > >  	char *mask_str = kmalloc(mask_len, GFP_KERNEL);
> > >  
> > 
> > DIV_ROUND_UP() is better?
> 
> Agreed


---
Subject: sched: fix the wrong mask_len
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Fri Oct 17 12:55:57 CEST 2008

If the NR_CPUS isn't a multiple of 32, we get a truncated string of sched
domains by catting /proc/schedstat. This is caused by the wrong mask_len.

Reported-by: Miao Xie <miaox@...fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
 kernel/sched_stats.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/kernel/sched_stats.h
===================================================================
--- linux-2.6.orig/kernel/sched_stats.h
+++ linux-2.6/kernel/sched_stats.h
@@ -9,7 +9,7 @@
 static int show_schedstat(struct seq_file *seq, void *v)
 {
 	int cpu;
-	int mask_len = NR_CPUS/32 * 9;
+	int mask_len = DIV_ROUND_UP(NR_CPUS, 32) * 9;
 	char *mask_str = kmalloc(mask_len, GFP_KERNEL);
 
 	if (mask_str == NULL)


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