On Wed 14-08-13 11:03:32, Linus Torvalds wrote:
> On Wed, Aug 14, 2013 at 10:40 AM, Michal Hocko <mhocko@xxxxxxx> wrote:
> >>
> >> After a _very long session of rebooting and bisecting_ the Linux kernel
> >> (fortunately I had a SSD and ccache!) I was able to pinpoint the cause
> >> to the following patch:
> >>
> >> *"mm: limit mmu_gather batching to fix soft lockups on !CONFIG_PREEMPT"*
> >> 787f7301074ccd07a3e82236ca41eefd245f4e07 linux stable [1]
> >> 53a59fc67f97374758e63a9c785891ec62324c81 upstream commit [2]
> >
> > Thanks for bisecting this up!
> >
> > I will look into this but I find it really strange.
>
> We had a TLB invalidation bug in the case when we ran out of page
> slots (and limiting the mmu_gather batching basically forcesd an early
> case of that).
>
> It was fixed in commit e6c495a96ce02574e765d5140039a64c8d4e8c9e ("mm:
> fix the TLB range flushed when __tlb_remove_page() runs out of
> slots"),
OK that would suggest the issue has been introduced by 597e1c35:
(mm/mmu_gather: enable tlb flush range in generic mmu_gather) in 3.6
which is not 3.7 when Ben started seeing the issue but this definitely
smells like a bug that would be amplified by the bisected patch.
Thanks for pointing this out, Linus!
> and that doesn't seem to have been marked for stable
> (probably because the commit message makes everytbody reading it think
> it's limited to ARC).
>
> Ben, can you try back-porting that commit from mainline and see if
> that fixes things?
>
> Linus
>
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--
Michal Hocko
SUSE Labs
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