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Groups > linux.kernel > #1412667
| From | Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup |
| Date | 2016-06-03 03:10 +0200 |
| Message-ID | <rFLMC-4Zt-9@gated-at.bofh.it> (permalink) |
| References | <rF4Rj-2Wb-13@gated-at.bofh.it> <rFq5s-7Xr-11@gated-at.bofh.it> <rFARb-6rl-1@gated-at.bofh.it> <rFG0x-1gi-11@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On (06/02/16 21:58), Ebru Akagunduz wrote:
[..]
> > I think it's this patch:
> >
> > http://ozlabs.org/~akpm/mmots/broken-out/mm-thp-make-swapin-readahead-under-down_read-of-mmap_sem.patch
> >
> > Some parts of the code in collapse_huge_page() that were under
> > down_write(mmap_sem) are under down_read() after the patch. But
> > there's "goto out" which continues via "goto out_up_write" which
> > does up_write(mmap_sem) so there's an imbalance. One path seems to
> > go via both up_read() and up_write(). I can imagine this can cause a
> > stuck down_write() among other things?
> Recently, I realized the same imbalance, it is an obvious
> inconsistency. I don't know, this issue can be related with
> mine. I'll send a fix patch.
a good find by Vlastimil.
Ebru, can you also re-visit __collapse_huge_page_swapin()? it's called
from collapse_huge_page() under the down_read(&mm->mmap_sem), is there
any reason to do the nested down_read(&mm->mmap_sem)?
collapse_huge_page()
...
down_read(&mm->mmap_sem);
result = hugepage_vma_revalidate(mm, vma, address);
if (result)
goto out;
pmd = mm_find_pmd(mm, address);
if (!pmd) {
result = SCAN_PMD_NULL;
goto out;
}
if (allocstall == curr_allocstall && swap != 0) {
if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) {
{
: if (ret & VM_FAULT_RETRY) {
: down_read(&mm->mmap_sem);
: ^^^^^^^^^
: if (hugepage_vma_revalidate(mm, vma, address))
: return false;
: }
}
up_read(&mm->mmap_sem);
goto out;
}
}
up_read(&mm->mmap_sem);
so if __collapse_huge_page_swapin() retruns true we have:
- down_read() twice, up_read() once?
the locking rules here are a bit confusing. (I didn't have my morning coffee yet).
-ss
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linux-next: Tree for Jun 1 Stephen Rothwell <sfr@canb.auug.org.au> - 2016-06-01 05:20 +0200
[linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-06-02 04:00 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Michal Hocko <mhocko@kernel.org> - 2016-06-02 11:30 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-06-02 14:10 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Michal Hocko <mhocko@kernel.org> - 2016-06-02 14:30 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Andrea Arcangeli <aarcange@redhat.com> - 2016-06-03 16:00 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Michal Hocko <mhocko@kernel.org> - 2016-06-03 16:50 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Andrea Arcangeli <aarcange@redhat.com> - 2016-06-03 17:20 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Michal Hocko <mhocko@kernel.org> - 2016-06-07 09:40 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Vlastimil Babka <vbabka@suse.cz> - 2016-06-08 10:20 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-06-03 09:20 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Michal Hocko <mhocko@kernel.org> - 2016-06-03 09:30 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-06-03 10:50 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Michal Hocko <mhocko@kernel.org> - 2016-06-03 12:00 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Michal Hocko <mhocko@kernel.org> - 2016-06-03 12:10 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-06-03 15:40 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Michal Hocko <mhocko@kernel.org> - 2016-06-03 15:50 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Michal Hocko <mhocko@kernel.org> - 2016-06-03 15:50 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-06-04 10:00 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Michal Hocko <mhocko@kernel.org> - 2016-06-06 10:40 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Vlastimil Babka <vbabka@suse.cz> - 2016-06-02 15:30 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Ebru Akagunduz <ebru.akagunduz@gmail.com> - 2016-06-02 21:00 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-06-03 03:10 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-06-03 03:30 +0200
Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-06-03 06:20 +0200
[PATCH] mm, thp: fix locking inconsistency in collapse_huge_page Ebru Akagunduz <ebru.akagunduz@gmail.com> - 2016-06-03 14:30 +0200
Re: [PATCH] mm, thp: fix locking inconsistency in collapse_huge_page Vlastimil Babka <vbabka@suse.cz> - 2016-06-06 15:10 +0200
Re: [PATCH] mm, thp: fix locking inconsistency in collapse_huge_page Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-06-09 06:00 +0200
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