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Groups > linux.kernel > #1332510
| From | "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) |
| Date | 2016-02-12 05:10 +0100 |
| Message-ID | <r1ddo-1Mt-3@gated-at.bofh.it> (permalink) |
| References | <r14a7-44q-17@gated-at.bofh.it> <r14MN-4Cs-9@gated-at.bofh.it> <r15zb-4W1-9@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Gerald Schaefer <gerald.schaefer@de.ibm.com> writes:
> On Thu, 11 Feb 2016 21:09:42 +0200
> "Kirill A. Shutemov" <kirill@shutemov.name> wrote:
>
>> On Thu, Feb 11, 2016 at 07:22:23PM +0100, Gerald Schaefer wrote:
>> > Hi,
>> >
>> > Sebastian Ott reported random kernel crashes beginning with v4.5-rc1 and
>> > he also bisected this to commit 61f5d698 "mm: re-enable THP". Further
>> > review of the THP rework patches, which cannot be bisected, revealed
>> > commit fecffad "s390, thp: remove infrastructure for handling splitting PMDs"
>> > (and also similar commits for other archs).
>> >
>> > This commit removes the THP splitting bit and also the architecture
>> > implementation of pmdp_splitting_flush(), which took care of the IPI for
>> > fast_gup serialization. The commit message says
>> >
>> > pmdp_splitting_flush() is not needed too: on splitting PMD we will do
>> > pmdp_clear_flush() + set_pte_at(). pmdp_clear_flush() will do IPI as
>> > needed for fast_gup
>> >
>> > The assumption that a TLB flush will also produce an IPI is wrong on s390,
>> > and maybe also on other architectures, and I thought that this was actually
>> > the main reason for having an arch-specific pmdp_splitting_flush().
>> >
>> > At least PowerPC and ARM also had an individual implementation of
>> > pmdp_splitting_flush() that used kick_all_cpus_sync() instead of a TLB
>> > flush to send the IPI, and those were also removed. Putting the arch
>> > maintainers and mailing lists on cc to verify.
>> >
>> > On s390 this will break the IPI serialization against fast_gup, which
>> > would certainly explain the random kernel crashes, please revert or fix
>> > the pmdp_splitting_flush() removal.
>>
>> Sorry for that.
>>
>> I believe, the problem was already addressed for PowerPC:
>>
>> http://lkml.kernel.org/g/454980831-16631-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com
>>
>> I think kick_all_cpus_sync() in arch-specific pmdp_invalidate() would do
>> the trick, right?
>
> Hmm, not sure about that. After pmdp_invalidate(), a pmd_none() check in
> fast_gup will still return false, because the pmd is not empty (at least
> on s390).
Why can't we do this ? I did this for ppc64.
void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp)
{
- pmd_hugepage_update(vma->vm_mm, address, pmdp, _PAGE_PRESENT, 0);
+ pmd_hugepage_update(vma->vm_mm, address, pmdp, ~0UL, 0);
>So I don't see spontaneously how it will help fast_gup to break
> out to the slow path in case of THP splitting.
>
>>
>> If yes, I'll prepare patch tomorrow (some sleep required).
>>
>
> We'll check if adding kick_all_cpus_sync() to pmdp_invalidate() helps.
> It would also be good if Martin has a look at this, he'll return on
> Monday.
-aneesh
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[BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Gerald Schaefer <gerald.schaefer@de.ibm.com> - 2016-02-11 19:30 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-02-11 20:10 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-02-11 20:20 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Sebastian Ott <sebott@linux.vnet.ibm.com> - 2016-02-12 13:30 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Gerald Schaefer <gerald.schaefer@de.ibm.com> - 2016-02-11 21:00 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> - 2016-02-12 05:10 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Gerald Schaefer <gerald.schaefer@de.ibm.com> - 2016-02-12 13:10 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> - 2016-02-12 17:20 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Will Deacon <will.deacon@arm.com> - 2016-02-12 11:10 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Sebastian Ott <sebott@linux.vnet.ibm.com> - 2016-02-12 11:20 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Will Deacon <will.deacon@arm.com> - 2016-02-12 17:00 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-02-12 16:50 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Christian Borntraeger <borntraeger@de.ibm.com> - 2016-02-12 17:00 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Gerald Schaefer <gerald.schaefer@de.ibm.com> - 2016-02-12 18:20 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-02-13 00:20 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Sebastian Ott <sebott@linux.vnet.ibm.com> - 2016-02-13 13:00 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-02-15 16:50 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Sebastian Ott <sebott@linux.vnet.ibm.com> - 2016-02-15 17:40 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Gerald Schaefer <gerald.schaefer@de.ibm.com> - 2016-02-15 19:40 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-02-16 00:30 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Sebastian Ott <sebott@linux.vnet.ibm.com> - 2016-02-16 11:00 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Gerald Schaefer <gerald.schaefer@de.ibm.com> - 2016-02-16 17:30 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-02-17 16:30 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Christian Borntraeger <borntraeger@de.ibm.com> - 2016-02-16 19:50 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Gerald Schaefer <gerald.schaefer@de.ibm.com> - 2016-02-17 20:20 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-02-18 08:00 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Gerald Schaefer <gerald.schaefer@de.ibm.com> - 2016-02-18 16:10 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-02-18 18:10 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Sebastian Ott <sebott@linux.vnet.ibm.com> - 2016-02-19 15:20 +0100
Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Gerald Schaefer <gerald.schaefer@de.ibm.com> - 2016-02-15 17:50 +0100
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