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SubjectRe: [PATCH] numa, mem-hotplug: Fix stack overflow in numa when seting kernel nodes to unhotpluggable.
On 01/28/2014 10:55 AM, Dave Jones wrote:
> On Tue, Jan 28, 2014 at 09:01:25AM +0800, Tang Chen wrote:
> > On 01/28/2014 08:32 AM, David Rientjes wrote:
> > > On Wed, 22 Jan 2014, David Rientjes wrote:
> > >
> > >>> arch/x86/mm/numa.c | 2 +-
> > >>> 1 file changed, 1 insertion(+), 1 deletion(-)
> > >>>
> > >>> diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> > >>> index 81b2750..ebefeb7 100644
> > >>> --- a/arch/x86/mm/numa.c
> > >>> +++ b/arch/x86/mm/numa.c
> > >>> @@ -562,10 +562,10 @@ static void __init numa_init_array(void)
> > >>> }
> > >>> }
> > >>>
> > >>> +static nodemask_t numa_kernel_nodes __initdata;
> > >>> static void __init numa_clear_kernel_node_hotplug(void)
> > >>> {
> > >>> int i, nid;
> > >>> - nodemask_t numa_kernel_nodes;
> > >>> unsigned long start, end;
> > >>> struct memblock_type *type =&memblock.reserved;
> > >>>
> > >>
> > >> Isn't this also a bugfix since you never initialize numa_kernel_nodes when
> > >> it's allocated on the stack with NODE_MASK_NONE?
> > >>
> > >
> > > This hasn't been answered and the patch still isn't in linux-kernel yet
> > > Dave tested it as good. I'm suspicious of the changelog that indicates
> > > this nodemask is the result of a stack overflow itself which only manages
> > > to reproduce itself in the init patch slightly more than 50% of the time.
> > > How is that possible?
> > >
> > > I think the changelog should indicate this also fixes an uninitialized
> > > nodemask issue.
> >
> > Hi David,
> >
> > I'm still working on this problem, but unfortunately nothing new for now.
> > And the test till now shows no more problem here.
> >
> > I'm digging into it, but need more time.
> >
> > I'll resend a new patch and modify the changelog soon. Before we find the
> > root cause, I think we can use this patch as a temporary solution.
>
> Ok, I hit the 2nd bug again (oops in next_zones_zonelist...)
>
> I did a bisect with the patch above applied each step of the way.
> This time I got a plausible looking result....

I cannot reproduce this. Would you please share how to reproduce it ?
Or does it just happen during the booting ?

>
>
> a0acda917284183f9b71e2d08b0aa0aea722b321 is the first bad commit
> commit a0acda917284183f9b71e2d08b0aa0aea722b321
> Author: Tang Chen<tangchen@cn.fujitsu.com>
> Date: Tue Jan 21 15:49:32 2014 -0800
>
> acpi, numa, mem_hotplug: mark all nodes the kernel resides un-hotpluggable
>
>
> Reverting this commit of course removes the whole function from above,
> so we haven't really learned anything new, other than that commit is broken,
> even after the above fix-up.
>
> Dave
>
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