The patch titled
Subject: mm: oom_kill: generalize OOM progress waitqueue
has been added to the -mm tree. Its filename is
mm-oom_kill-generalize-oom-progress-waitqueue.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-oom_kill-generalize-oom-progress-waitqueue.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-oom_kill-generalize-oom-progress-waitqueue.patch
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------------------------------------------------------
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: mm: oom_kill: generalize OOM progress waitqueue
It turns out that the mechanism to wait for exiting OOM victims is less
generic than it looks: it won't issue wakeups unless the OOM killer is
disabled.
The reason this check was added was the thought that, since only the OOM
disabling code would wait on this queue, wakeup operations could be saved
when that specific consumer is known to be absent.
However, this is quite the handgrenade. Later attempts to reuse the
waitqueue for other purposes will lead to completely unexpected bugs and
the failure mode will appear seemingly illogical. Generally, providers
shouldn't make unnecessary assumptions about consumers.
This could have been replaced with waitqueue_active(), but it only saves a
few instructions in one of the coldest paths in the kernel. Simply remove
it.
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/oom_kill.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff -puN mm/oom_kill.c~mm-oom_kill-generalize-oom-progress-waitqueue mm/oom_kill.c
--- a/mm/oom_kill.c~mm-oom_kill-generalize-oom-progress-waitqueue
+++ a/mm/oom_kill.c
@@ -438,11 +438,7 @@ void exit_oom_victim(void)
clear_thread_flag(TIF_MEMDIE);
down_read(&oom_sem);
- /*
- * There is no need to signal the lasst oom_victim if there
- * is nobody who cares.
- */
- if (!atomic_dec_return(&oom_victims) && oom_killer_disabled)
+ if (!atomic_dec_return(&oom_victims))
wake_up_all(&oom_victims_wait);
up_read(&oom_sem);
}
_
Patches currently in -mm which might be from hannes@xxxxxxxxxxx are
jbd2-revert-must-not-fail-allocation-loops-back-to-gfp_nofail.patch
mm-vmscan-do-not-throttle-based-on-pfmemalloc-reserves-if-node-has-no-reclaimable-pages.patch
rename-reclaim_swap-to-reclaim_unmap.patch
userfaultfd-linux-documentation-vm-userfaultfdtxt.patch
userfaultfd-waitqueue-add-nr-wake-parameter-to-__wake_up_locked_key.patch
userfaultfd-uapi.patch
userfaultfd-linux-userfaultfd_kh.patch
userfaultfd-add-vm_userfaultfd_ctx-to-the-vm_area_struct.patch
userfaultfd-add-vm_uffd_missing-and-vm_uffd_wp.patch
userfaultfd-call-handle_userfault-for-userfaultfd_missing-faults.patch
userfaultfd-teach-vma_merge-to-merge-across-vma-vm_userfaultfd_ctx.patch
userfaultfd-prevent-khugepaged-to-merge-if-userfaultfd-is-armed.patch
userfaultfd-add-new-syscall-to-provide-memory-externalization.patch
userfaultfd-rename-uffd_apibits-into-features.patch
userfaultfd-rename-uffd_apibits-into-features-fixup.patch
userfaultfd-change-the-read-api-to-return-a-uffd_msg.patch
userfaultfd-wake-pending-userfaults.patch
userfaultfd-optimize-read-and-poll-to-be-o1.patch
userfaultfd-allocate-the-userfaultfd_ctx-cacheline-aligned.patch
userfaultfd-solve-the-race-between-uffdio_copyzeropage-and-read.patch
userfaultfd-buildsystem-activation.patch
userfaultfd-activate-syscall.patch
userfaultfd-uffdio_copyuffdio_zeropage-uapi.patch
userfaultfd-mcopy_atomicmfill_zeropage-uffdio_copyuffdio_zeropage-preparation.patch
userfaultfd-avoid-mmap_sem-read-recursion-in-mcopy_atomic.patch
userfaultfd-uffdio_copy-and-uffdio_zeropage.patch
mm-oom_kill-remove-unnecessary-locking-in-oom_enable.patch
mm-oom_kill-clean-up-victim-marking-and-exiting-interfaces.patch
mm-oom_kill-switch-test-and-clear-of-known-tif_memdie-to-clear.patch
mm-oom_kill-generalize-oom-progress-waitqueue.patch
mm-oom_kill-remove-unnecessary-locking-in-exit_oom_victim.patch
mm-oom_kill-simplify-oom-killer-locking.patch
mm-page_alloc-inline-should_alloc_retry.patch
page-flags-trivial-cleanup-for-pagetrans-helpers.patch
page-flags-introduce-page-flags-policies-wrt-compound-pages.patch
page-flags-define-pg_locked-behavior-on-compound-pages.patch
page-flags-define-behavior-of-fs-io-related-flags-on-compound-pages.patch
page-flags-define-behavior-of-lru-related-flags-on-compound-pages.patch
page-flags-define-behavior-slb-related-flags-on-compound-pages.patch
page-flags-define-behavior-of-xen-related-flags-on-compound-pages.patch
page-flags-define-pg_reserved-behavior-on-compound-pages.patch
page-flags-define-pg_swapbacked-behavior-on-compound-pages.patch
page-flags-define-pg_swapcache-behavior-on-compound-pages.patch
page-flags-define-pg_mlocked-behavior-on-compound-pages.patch
page-flags-define-pg_uncached-behavior-on-compound-pages.patch
page-flags-define-pg_uptodate-behavior-on-compound-pages.patch
page-flags-look-on-head-page-if-the-flag-is-encoded-in-page-mapping.patch
mm-sanitize-page-mapping-for-tail-pages.patch
mm-vmscan-fix-the-page-state-calculation-in-too_many_isolated.patch
mm-move-lazy-free-pages-to-inactive-list.patch
mm-move-lazy-free-pages-to-inactive-list-fix.patch
mm-move-lazy-free-pages-to-inactive-list-fix-fix.patch
radix-tree-replace-preallocated-node-array-with-linked-list.patch
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