lkml.org 
[lkml]   [2016]   [Nov]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [RFC PATCH] perf/x86/intel/rapl: avoid access unallocate memory
From
Date
On 11/02/2016 08:25 AM, Sebastian Andrzej Siewior wrote:
> I am not sure if this a race with the new hotplug code or something that was
> always there. Both (M. Vefa Bicakc and Charles) say that the box boots
> sometimes fine (without the patch). smp_store_boot_cpu_info() should have run
> before the notofoert and thus should have set the info properly. However I got
> the following bootlog from Charles with this patch:

I don't this this is a race. Here is some debugging from the two CPU VM
(2 sockets, 1 core per socket). In identify_cpu() we have:

/* The boot/hotplug time assigment got cleared, restore it */
c->logical_proc_id = topology_phys_to_logical_pkg(c->phys_proc_id);

The values just after this:

[ 0.228306] identify_cpu: c ffff88023fd0a040 logical_proc_id 65535 c->phys_proc_id 2

So what's interesting here, is the phys_proc_id of 2 for CPU1:

int topology_phys_to_logical_pkg(unsigned int phys_pkg)
{
if (phys_pkg >= max_physical_pkg_id)
return -1;
return physical_to_logical_pkg[phys_pkg];
}

And we happen to know the max_physical_pkg_id is 2 in this case.
So apparently, topology_phys_to_logical_pkg() returns -1 and it gets
assigned to the logical_proc_id.

I don't know why the CPU's phys_proc_id is 2.

\
 
 \ /
  Last update: 2016-11-02 23:48    [W:0.096 / U:0.516 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site