Re: wrong parsing to /proc/self/status causes wrong out-of-range errors

[Cliff Wickman <cpw@sgi.com>]

Hi Brice,

Thanks for the fix.

I tested it on ia64.
It is now part of numactl-2.0.3-rc2.tar.gz at
ftp://oss.sgi.com/www/projects/libnuma/download/

BTW,
Andi, Lee and all,
We have no established release schedule that I'm aware of.
2.0.2 was Aug08
There are about 14 fixes accumulated in 2.0.3 rc1 and rc2.  But only
a trickle of small changes lately.
I'm inclined to announce it as 2.0.3, if you have used it and are
satisfied that it's stable.

-Cliff

On Tue, Apr 21, 2009 at 05:48:18PM +0200, Brice Goglin wrote:
> Hello,
> 
> After upgrading a quad-socket quad-core machine from 2.6.27 to 2.6.29,
> numactl now reports that --physcpubind=X is an out-of-range CPU when
> 12<=X<16
> (while obviously we still have 16 cores in this machine).
> Same problem on other machines with 2.6.29: the last 4 cores are
> "out-of-range".
> First observed with Debian's 2.0.3-rc1 but seems to occur with 2.0.3-rc2
> as well.
> 
> It appears that this is caused by set_thread_constraints() passing a
> wrong pointer to read_mask() when trying to gather maxproccpu and
> maxprocnode from /proc/self/status. It points to the second character
> of the mask instead of the first one, thus loosing one "f", which means
> 4 cores are lost.
> 
> The kernel code generating the "Cpus_allowed:" and "Mems_allowed:" masks
> in /proc/self/status has changed recently, so maybe the formatting
> changed a bit (whitespaces?).
> 
> The patch below fixes this problem by just passing a pointer to the first
> character after ":". read_mask/strtoul are able to skip whitespaces anyway,
> so no need to bother trying to guess how many whitespaces follow ":" in the
> caller.
> 
> Brice
> 
> 
> Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
> 
> diff -ur numactl-2.0.3~rc1/libnuma.c numactl-2.0.3~rc1.save/libnuma.c
> --- numactl-2.0.3~rc1/libnuma.c	2008-12-09 20:38:07.000000000 +0100
> +++ numactl-2.0.3~rc1.save/libnuma.c	2009-04-21 15:44:19.000000000 +0200
> @@ -479,11 +479,11 @@
>  
>  	while (getline(&buffer, &buflen, f) > 0) {
>  		if (strncmp(buffer,"Cpus_allowed:",13) == 0)
> -			maxproccpu = read_mask(buffer + 15, numa_all_cpus_ptr);
> +			maxproccpu = read_mask(buffer + 13, numa_all_cpus_ptr);
>  
>  		if (strncmp(buffer,"Mems_allowed:",13) == 0) {
>  			maxprocnode =
> -				read_mask(buffer + 15, numa_all_nodes_ptr);
> +				read_mask(buffer + 13, numa_all_nodes_ptr);
>  		}
>  	}
>  	fclose(f);
> 
> 
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-- 
Cliff Wickman
Silicon Graphics, Inc.
cpw@sgi.com
(651) 683-3824