Re: [Crash-utility] kmem -[sS] segfault on 2.6.25.17
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----- "Mike Snitzer" <snitzer(a)gmail.com> wrote:
I'm getting a core when I try to show slab data (kmem -[sS]) on
2.6.25.17 with both a live crash or saved vmcore.
The core shows that the segv is coming from memset() via
gather_cpudata_list_v2_nodes (memory.c:10119). This is with crash
4.0-7.4, but the same crash occurs with crash 4.0-6.3
(memory.c:10108)
and older.
I've also seen kmem -[sS] segfaults with older kernels too (e.g.
2.6.22.x).
Have others experienced this? Would it be useful for me to provide
my
kernel config?
No that won't help.
It's failing in the BZERO() here:
10117 for (i = 0; (i < ARRAY_LENGTH(kmem_cache_s_array)) &&
10118 (cpudata[i]) && !(index); i++) {
10119 BZERO(si->cpudata[i], sizeof(ulong) * vt->kmem_max_limit);
What is "i" equal to when it segfaults? If you have a crash core file,
print out the contents of the global "vm_table". In that structure
there is a "kmem_max_cpus" field. If "i" is greater or equal to
that,
then that's one explanation.
Or you can bring up the dumpfile (or live system), and look at the value
kmem_max_cpus by looking at the output of "help -v".
Dave
Dave
Mike Snitzer
Thursday, 16 October
Thu, 16 Oct
11:41 a.m.
New subject: kmem -[sS] segfault on 2.6.25.17
On Thu, Oct 16, 2008 at 12:25 PM, Dave Anderson <anderson(a)redhat.com> wrote:
----- "Mike Snitzer" <snitzer(a)gmail.com> wrote:
> I'm getting a core when I try to show slab data (kmem -[sS]) on
> 2.6.25.17 with both a live crash or saved vmcore.
>
> The core shows that the segv is coming from memset() via
> gather_cpudata_list_v2_nodes (memory.c:10119). This is with crash
> 4.0-7.4, but the same crash occurs with crash 4.0-6.3
> (memory.c:10108)
> and older.
>
> I've also seen kmem -[sS] segfaults with older kernels too (e.g.
> 2.6.22.x).
>
> Have others experienced this? Would it be useful for me to provide
> my
> kernel config?
No that won't help.
Actually I think it may considering kmem -[sS] works perfectly fine on
the same identical 2.6.22.19 kernel if various debug features are
_not_ enabled, see the attached .config diff. Of note:
-# CONFIG_DEBUG_SLAB is not set
+CONFIG_DEBUG_SLAB=y
+CONFIG_DEBUG_SLAB_LEAK=y
Comparable debug features are enabled in my 2.6.25 kernel that causes
crash to segfault.
It's failing in the BZERO() here:
10117 for (i = 0; (i < ARRAY_LENGTH(kmem_cache_s_array)) &&
10118 (cpudata[i]) && !(index); i++) {
10119 BZERO(si->cpudata[i], sizeof(ulong) * vt->kmem_max_limit);
What is "i" equal to when it segfaults? If you have a crash core file,
print out the contents of the global "vm_table". In that structure
there is a "kmem_max_cpus" field. If "i" is greater or equal to
that,
then that's one explanation.
i=0 and kmem_max_cpus=4.
thanks,
Mike
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