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[PATCH 11/18] coredump: make coredump_wait wait for mmap_sem for write killable

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From: Michal Hocko <mhocko@suse.com>

coredump_wait waits for mmap_sem for write currently which can
prevent oom_reaper to reclaim the oom victims address space
asynchronously because that requires mmap_sem for read. This might
happen if the oom victim is multi threaded and some thread(s) is
holding mmap_sem for read (e.g. page fault) and it is stuck in
the page allocator while other thread(s) reached coredump_wait
already.

This patch simply uses down_write_killable and bails out with EINTR
if the lock got interrupted by the fatal signal. do_coredump will
return right away and do_group_exit will take care to zap the whole
thread group.

Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 fs/coredump.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index 47c32c3bfa1d..f2cef927789b 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -413,7 +413,9 @@ static int coredump_wait(int exit_code, struct core_state *core_state)
 	core_state->dumper.task = tsk;
 	core_state->dumper.next = NULL;
 
-	down_write(&mm->mmap_sem);
+	if (down_write_killable(&mm->mmap_sem))
+		return -EINTR;
+
 	if (!mm->core_state)
 		core_waiters = zap_threads(tsk, mm, core_state, exit_code);
 	up_write(&mm->mmap_sem);
-- 
2.8.0.rc3

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[PATCH 0/18] change mmap_sem taken for write killable v2 Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 09/18] ipc, shm: make shmem attach/detach wait for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 07/18] mm, proc: make clear_refs killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 13/18] exec: make exec path waiting for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 06/18] mm: make vm_brk killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 18/18] drm/amdgpu: make amdgpu_mn_get wait for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 03/18] mm: make vm_munmap killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 08/18] mm, fork: make dup_mmap wait for mmap_sem for write killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 14/18] prctl: make PR_SET_THP_DISABLE wait for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
    Re: [PATCH 14/18] prctl: make PR_SET_THP_DISABLE wait for mmap_sem  killable Alex Thorlton <athorlton@sgi.com> - 2016-04-26 17:20 +0200
  [PATCH 16/18] drm/i915: make i915_gem_mmap_ioctl wait for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 10/18] vdso: make arch_setup_additional_pages wait for mmap_sem for write killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 02/18] mm: make vm_mmap killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 11/18] coredump: make coredump_wait wait for mmap_sem for write killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 12/18] aio: make aio_setup_ring killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 04/18] mm, aout: handle vm_brk failures Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:10 +0200
  [PATCH 05/18] mm, elf: handle vm_brk error Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:10 +0200
  [PATCH 01/18] mm: Make mmap_sem for write waits killable for mm syscalls Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:10 +0200

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