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  1. 14 12月, 2014 1 次提交
    • O
      oom: don't assume that a coredumping thread will exit soon · d003f371
      由 Oleg Nesterov 提交于 
      oom_kill.c assumes that PF_EXITING task should exit and free the memory
soon.  This is wrong in many ways and one important case is the coredump.
A task can sleep in exit_mm() "forever" while the coredumping sub-thread
can need more memory.

Change the PF_EXITING checks to take SIGNAL_GROUP_COREDUMP into account,
we add the new trivial helper for that.

Note: this is only the first step, this patch doesn't try to solve other
problems.  The SIGNAL_GROUP_COREDUMP check is obviously racy, a task can
participate in coredump after it was already observed in PF_EXITING state,
so TIF_MEMDIE (which also blocks oom-killer) still can be wrongly set.
fatal_signal_pending() can be true because of SIGNAL_GROUP_COREDUMP so
out_of_memory() and mem_cgroup_out_of_memory() shouldn't blindly trust it.
 And even the name/usage of the new helper is confusing, an exiting thread
can only free its ->mm if it is the only/last task in thread group.

[akpm@linux-foundation.org: add comment]
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d003f371
  3. 11 12月, 2014 1 次提交
  5. 27 10月, 2014 1 次提交
    • V
      cpuset: simplify cpuset_node_allowed API · 344736f2
      由 Vladimir Davydov 提交于 
      Current cpuset API for checking if a zone/node is allowed to allocate
from looks rather awkward. We have hardwall and softwall versions of
cpuset_node_allowed with the softwall version doing literally the same
as the hardwall version if __GFP_HARDWALL is passed to it in gfp flags.
If it isn't, the softwall version may check the given node against the
enclosing hardwall cpuset, which it needs to take the callback lock to
do.

Such a distinction was introduced by commit 02a0e53d ("cpuset:
rework cpuset_zone_allowed api"). Before, we had the only version with
the __GFP_HARDWALL flag determining its behavior. The purpose of the
commit was to avoid sleep-in-atomic bugs when someone would mistakenly
call the function without the __GFP_HARDWALL flag for an atomic
allocation. The suffixes introduced were intended to make the callers
think before using the function.

However, since the callback lock was converted from mutex to spinlock by
the previous patch, the softwall check function cannot sleep, and these
precautions are no longer necessary.

So let's simplify the API back to the single check.
Suggested-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NVladimir Davydov <vdavydov@parallels.com>
Acked-by: NChristoph Lameter <cl@linux.com>
Acked-by: NZefan Li <lizefan@huawei.com>
Signed-off-by: NTejun Heo <tj@kernel.org>
      344736f2
  7. 22 10月, 2014 1 次提交
    • M
      OOM, PM: OOM killed task shouldn't escape PM suspend · 5695be14
      由 Michal Hocko 提交于 
      PM freezer relies on having all tasks frozen by the time devices are
getting frozen so that no task will touch them while they are getting
frozen. But OOM killer is allowed to kill an already frozen task in
order to handle OOM situtation. In order to protect from late wake ups
OOM killer is disabled after all tasks are frozen. This, however, still
keeps a window open when a killed task didn't manage to die by the time
freeze_processes finishes.

Reduce the race window by checking all tasks after OOM killer has been
disabled. This is still not race free completely unfortunately because
oom_killer_disable cannot stop an already ongoing OOM killer so a task
might still wake up from the fridge and get killed without
freeze_processes noticing. Full synchronization of OOM and freezer is,
however, too heavy weight for this highly unlikely case.

Introduce and check oom_kills counter which gets incremented early when
the allocator enters __alloc_pages_may_oom path and only check all the
tasks if the counter changes during the freezing attempt. The counter
is updated so early to reduce the race window since allocator checked
oom_killer_disabled which is set by PM-freezing code. A false positive
will push the PM-freezer into a slow path but that is not a big deal.

Changes since v1
- push the re-check loop out of freeze_processes into
  check_frozen_processes and invert the condition to make the code more
  readable as per Rafael

Fixes: f660daac (oom: thaw threads if oom killed thread is frozen before deferring)
Cc: 3.2+ <stable@vger.kernel.org> # 3.2+
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      5695be14
  9. 10 10月, 2014 1 次提交
  11. 07 8月, 2014 3 次提交
    • D
      mm, oom: remove unnecessary exit_state check · fb794bcb
      由 David Rientjes 提交于 
      The oom killer scans each process and determines whether it is eligible
for oom kill or whether the oom killer should abort because of
concurrent memory freeing.  It will abort when an eligible process is
found to have TIF_MEMDIE set, meaning it has already been oom killed and
we're waiting for it to exit.

Processes with task->mm == NULL should not be considered because they
are either kthreads or have already detached their memory and killing
them would not lead to memory freeing.  That memory is only freed after
exit_mm() has returned, however, and not when task->mm is first set to
NULL.

Clear TIF_MEMDIE after exit_mm()'s mmput() so that an oom killed process
is no longer considered for oom kill, but only until exit_mm() has
returned.  This was fragile in the past because it relied on
exit_notify() to be reached before no longer considering TIF_MEMDIE
processes.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      fb794bcb
    • D
      mm, oom: rename zonelist locking functions · e972a070
      由 David Rientjes 提交于 
      try_set_zonelist_oom() and clear_zonelist_oom() are not named properly
to imply that they require locking semantics to avoid out_of_memory()
being reordered.

zone_scan_lock is required for both functions to ensure that there is
proper locking synchronization.

Rename try_set_zonelist_oom() to oom_zonelist_trylock() and rename
clear_zonelist_oom() to oom_zonelist_unlock() to imply there is proper
locking semantics.

At the same time, convert oom_zonelist_trylock() to return bool instead
of int since only success and failure are tested.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e972a070
    • D
      mm, oom: ensure memoryless node zonelist always includes zones · 8d060bf4
      由 David Rientjes 提交于 
      With memoryless node support being worked on, it's possible that for
optimizations that a node may not have a non-NULL zonelist.  When
CONFIG_NUMA is enabled and node 0 is memoryless, this means the zonelist
for first_online_node may become NULL.

The oom killer requires a zonelist that includes all memory zones for
the sysrq trigger and pagefault out of memory handler.

Ensure that a non-NULL zonelist is always passed to the oom killer.

[akpm@linux-foundation.org: fix non-numa build]
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      8d060bf4
  13. 31 1月, 2014 1 次提交
    • D
      mm, oom: base root bonus on current usage · 778c14af
      由 David Rientjes 提交于 
      A 3% of system memory bonus is sometimes too excessive in comparison to
other processes.

With commit a63d83f4 ("oom: badness heuristic rewrite"), the OOM
killer tries to avoid killing privileged tasks by subtracting 3% of
overall memory (system or cgroup) from their per-task consumption.  But
as a result, all root tasks that consume less than 3% of overall memory
are considered equal, and so it only takes 33+ privileged tasks pushing
the system out of memory for the OOM killer to do something stupid and
kill dhclient or other root-owned processes.  For example, on a 32G
machine it can't tell the difference between the 1M agetty and the 10G
fork bomb member.

The changelog describes this 3% boost as the equivalent to the global
overcommit limit being 3% higher for privileged tasks, but this is not
the same as discounting 3% of overall memory from _every privileged task
individually_ during OOM selection.

Replace the 3% of system memory bonus with a 3% of current memory usage
bonus.

By giving root tasks a bonus that is proportional to their actual size,
they remain comparable even when relatively small.  In the example
above, the OOM killer will discount the 1M agetty's 256 badness points
down to 179, and the 10G fork bomb's 262144 points down to 183500 points
and make the right choice, instead of discounting both to 0 and killing
agetty because it's first in the task list.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Reported-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      778c14af
  15. 24 1月, 2014 1 次提交
  17. 22 1月, 2014 3 次提交
  19. 15 11月, 2013 1 次提交
    • K
      mm: convert mm->nr_ptes to atomic_long_t · e1f56c89
      由 Kirill A. Shutemov 提交于 
      With split page table lock for PMD level we can't hold mm->page_table_lock
while updating nr_ptes.

Let's convert it to atomic_long_t to avoid races.
Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: NAlex Thorlton <athorlton@sgi.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Jones <davej@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Robin Holt <robinmholt@gmail.com>
Cc: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e1f56c89
  21. 17 10月, 2013 1 次提交
    • J
      mm: memcg: handle non-error OOM situations more gracefully · 49426420
      由 Johannes Weiner 提交于 
      Commit 3812c8c8 ("mm: memcg: do not trap chargers with full
callstack on OOM") assumed that only a few places that can trigger a
memcg OOM situation do not return VM_FAULT_OOM, like optional page cache
readahead.  But there are many more and it's impractical to annotate
them all.

First of all, we don't want to invoke the OOM killer when the failed
allocation is gracefully handled, so defer the actual kill to the end of
the fault handling as well.  This simplifies the code quite a bit for
added bonus.

Second, since a failed allocation might not be the abrupt end of the
fault, the memcg OOM handler needs to be re-entrant until the fault
finishes for subsequent allocation attempts.  If an allocation is
attempted after the task already OOMed, allow it to bypass the limit so
that it can quickly finish the fault and invoke the OOM killer.
Reported-by: NazurIt <azurit@pobox.sk>
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      49426420
  23. 13 9月, 2013 1 次提交
    • J
      mm: memcg: do not trap chargers with full callstack on OOM · 3812c8c8
      由 Johannes Weiner 提交于 
      The memcg OOM handling is incredibly fragile and can deadlock.  When a
task fails to charge memory, it invokes the OOM killer and loops right
there in the charge code until it succeeds.  Comparably, any other task
that enters the charge path at this point will go to a waitqueue right
then and there and sleep until the OOM situation is resolved.  The problem
is that these tasks may hold filesystem locks and the mmap_sem; locks that
the selected OOM victim may need to exit.

For example, in one reported case, the task invoking the OOM killer was
about to charge a page cache page during a write(), which holds the
i_mutex.  The OOM killer selected a task that was just entering truncate()
and trying to acquire the i_mutex:

OOM invoking task:
  mem_cgroup_handle_oom+0x241/0x3b0
  mem_cgroup_cache_charge+0xbe/0xe0
  add_to_page_cache_locked+0x4c/0x140
  add_to_page_cache_lru+0x22/0x50
  grab_cache_page_write_begin+0x8b/0xe0
  ext3_write_begin+0x88/0x270
  generic_file_buffered_write+0x116/0x290
  __generic_file_aio_write+0x27c/0x480
  generic_file_aio_write+0x76/0xf0           # takes ->i_mutex
  do_sync_write+0xea/0x130
  vfs_write+0xf3/0x1f0
  sys_write+0x51/0x90
  system_call_fastpath+0x18/0x1d

OOM kill victim:
  do_truncate+0x58/0xa0              # takes i_mutex
  do_last+0x250/0xa30
  path_openat+0xd7/0x440
  do_filp_open+0x49/0xa0
  do_sys_open+0x106/0x240
  sys_open+0x20/0x30
  system_call_fastpath+0x18/0x1d

The OOM handling task will retry the charge indefinitely while the OOM
killed task is not releasing any resources.

A similar scenario can happen when the kernel OOM killer for a memcg is
disabled and a userspace task is in charge of resolving OOM situations.
In this case, ALL tasks that enter the OOM path will be made to sleep on
the OOM waitqueue and wait for userspace to free resources or increase
the group's limit.  But a userspace OOM handler is prone to deadlock
itself on the locks held by the waiting tasks.  For example one of the
sleeping tasks may be stuck in a brk() call with the mmap_sem held for
writing but the userspace handler, in order to pick an optimal victim,
may need to read files from /proc/<pid>, which tries to acquire the same
mmap_sem for reading and deadlocks.

This patch changes the way tasks behave after detecting a memcg OOM and
makes sure nobody loops or sleeps with locks held:

1. When OOMing in a user fault, invoke the OOM killer and restart the
   fault instead of looping on the charge attempt.  This way, the OOM
   victim can not get stuck on locks the looping task may hold.

2. When OOMing in a user fault but somebody else is handling it
   (either the kernel OOM killer or a userspace handler), don't go to
   sleep in the charge context.  Instead, remember the OOMing memcg in
   the task struct and then fully unwind the page fault stack with
   -ENOMEM.  pagefault_out_of_memory() will then call back into the
   memcg code to check if the -ENOMEM came from the memcg, and then
   either put the task to sleep on the memcg's OOM waitqueue or just
   restart the fault.  The OOM victim can no longer get stuck on any
   lock a sleeping task may hold.

Debugged by Michal Hocko.
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Reported-by: NazurIt <azurit@pobox.sk>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3812c8c8
  25. 15 7月, 2013 1 次提交
  27. 24 2月, 2013 1 次提交
    • S
      memcg, oom: provide more precise dump info while memcg oom happening · 58cf188e
      由 Sha Zhengju 提交于 
      Currently when a memcg oom is happening the oom dump messages is still
global state and provides few useful info for users.  This patch prints
more pointed memcg page statistics for memcg-oom and take hierarchy into
consideration:

Based on Michal's advice, we take hierarchy into consideration: supppose
we trigger an OOM on A's limit

        root_memcg
            |
            A (use_hierachy=1)
           / \
          B   C
          |
          D
then the printed info will be:

  Memory cgroup stats for /A:...
  Memory cgroup stats for /A/B:...
  Memory cgroup stats for /A/C:...
  Memory cgroup stats for /A/B/D:...

Following are samples of oom output:

(1) Before change:

    mal-80 invoked oom-killer:gfp_mask=0xd0, order=0, oom_score_adj=0
    mal-80 cpuset=/ mems_allowed=0
    Pid: 2976, comm: mal-80 Not tainted 3.7.0+ #10
    Call Trace:
     [<ffffffff8167fbfb>] dump_header+0x83/0x1ca
     ..... (call trace)
     [<ffffffff8168a818>] page_fault+0x28/0x30
                             <<<<<<<<<<<<<<<<<<<<< memcg specific information
    Task in /A/B/D killed as a result of limit of /A
    memory: usage 101376kB, limit 101376kB, failcnt 57
    memory+swap: usage 101376kB, limit 101376kB, failcnt 0
    kmem: usage 0kB, limit 9007199254740991kB, failcnt 0
                             <<<<<<<<<<<<<<<<<<<<< print per cpu pageset stat
    Mem-Info:
    Node 0 DMA per-cpu:
    CPU    0: hi:    0, btch:   1 usd:   0
    ......
    CPU    3: hi:    0, btch:   1 usd:   0
    Node 0 DMA32 per-cpu:
    CPU    0: hi:  186, btch:  31 usd: 173
    ......
    CPU    3: hi:  186, btch:  31 usd: 130
                             <<<<<<<<<<<<<<<<<<<<< print global page state
    active_anon:92963 inactive_anon:40777 isolated_anon:0
     active_file:33027 inactive_file:51718 isolated_file:0
     unevictable:0 dirty:3 writeback:0 unstable:0
     free:729995 slab_reclaimable:6897 slab_unreclaimable:6263
     mapped:20278 shmem:35971 pagetables:5885 bounce:0
     free_cma:0
                             <<<<<<<<<<<<<<<<<<<<< print per zone page state
    Node 0 DMA free:15836kB ... all_unreclaimable? no
    lowmem_reserve[]: 0 3175 3899 3899
    Node 0 DMA32 free:2888564kB ... all_unrelaimable? no
    lowmem_reserve[]: 0 0 724 724
    lowmem_reserve[]: 0 0 0 0
    Node 0 DMA: 1*4kB (U) ... 3*4096kB (M) = 15836kB
    Node 0 DMA32: 41*4kB (UM) ... 702*4096kB (MR) = 2888316kB
    120710 total pagecache pages
    0 pages in swap cache
                             <<<<<<<<<<<<<<<<<<<<< print global swap cache stat
    Swap cache stats: add 0, delete 0, find 0/0
    Free swap  = 499708kB
    Total swap = 499708kB
    1040368 pages RAM
    58678 pages reserved
    169065 pages shared
    173632 pages non-shared
    [ pid ]   uid  tgid total_vm      rss nr_ptes swapents oom_score_adj name
    [ 2693]     0  2693     6005     1324      17        0             0 god
    [ 2754]     0  2754     6003     1320      16        0             0 god
    [ 2811]     0  2811     5992     1304      18        0             0 god
    [ 2874]     0  2874     6005     1323      18        0             0 god
    [ 2935]     0  2935     8720     7742      21        0             0 mal-30
    [ 2976]     0  2976    21520    17577      42        0             0 mal-80
    Memory cgroup out of memory: Kill process 2976 (mal-80) score 665 or sacrifice child
    Killed process 2976 (mal-80) total-vm:86080kB, anon-rss:69964kB, file-rss:344kB

We can see that messages dumped by show_free_areas() are longsome and can
provide so limited info for memcg that just happen oom.

(2) After change
    mal-80 invoked oom-killer: gfp_mask=0xd0, order=0, oom_score_adj=0
    mal-80 cpuset=/ mems_allowed=0
    Pid: 2704, comm: mal-80 Not tainted 3.7.0+ #10
    Call Trace:
     [<ffffffff8167fd0b>] dump_header+0x83/0x1d1
     .......(call trace)
     [<ffffffff8168a918>] page_fault+0x28/0x30
    Task in /A/B/D killed as a result of limit of /A
                             <<<<<<<<<<<<<<<<<<<<< memcg specific information
    memory: usage 102400kB, limit 102400kB, failcnt 140
    memory+swap: usage 102400kB, limit 102400kB, failcnt 0
    kmem: usage 0kB, limit 9007199254740991kB, failcnt 0
    Memory cgroup stats for /A: cache:32KB rss:30984KB mapped_file:0KB swap:0KB inactive_anon:6912KB active_anon:24072KB inactive_file:32KB active_file:0KB unevictable:0KB
    Memory cgroup stats for /A/B: cache:0KB rss:0KB mapped_file:0KB swap:0KB inactive_anon:0KB active_anon:0KB inactive_file:0KB active_file:0KB unevictable:0KB
    Memory cgroup stats for /A/C: cache:0KB rss:0KB mapped_file:0KB swap:0KB inactive_anon:0KB active_anon:0KB inactive_file:0KB active_file:0KB unevictable:0KB
    Memory cgroup stats for /A/B/D: cache:32KB rss:71352KB mapped_file:0KB swap:0KB inactive_anon:6656KB active_anon:64696KB inactive_file:16KB active_file:16KB unevictable:0KB
    [ pid ]   uid  tgid total_vm      rss nr_ptes swapents oom_score_adj name
    [ 2260]     0  2260     6006     1325      18        0             0 god
    [ 2383]     0  2383     6003     1319      17        0             0 god
    [ 2503]     0  2503     6004     1321      18        0             0 god
    [ 2622]     0  2622     6004     1321      16        0             0 god
    [ 2695]     0  2695     8720     7741      22        0             0 mal-30
    [ 2704]     0  2704    21520    17839      43        0             0 mal-80
    Memory cgroup out of memory: Kill process 2704 (mal-80) score 669 or sacrifice child
    Killed process 2704 (mal-80) total-vm:86080kB, anon-rss:71016kB, file-rss:340kB

This version provides more pointed info for memcg in "Memory cgroup stats
for XXX" section.
Signed-off-by: NSha Zhengju <handai.szj@taobao.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      58cf188e
  29. 13 12月, 2012 3 次提交
  31. 12 12月, 2012 3 次提交
    • D
      mm, oom: fix race when specifying a thread as the oom origin · e1e12d2f
      由 David Rientjes 提交于 
      test_set_oom_score_adj() and compare_swap_oom_score_adj() are used to
specify that current should be killed first if an oom condition occurs in
between the two calls.

The usage is

	short oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX);
	...
	compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX, oom_score_adj);

to store the thread's oom_score_adj, temporarily change it to the maximum
score possible, and then restore the old value if it is still the same.

This happens to still be racy, however, if the user writes
OOM_SCORE_ADJ_MAX to /proc/pid/oom_score_adj in between the two calls.
The compare_swap_oom_score_adj() will then incorrectly reset the old value
prior to the write of OOM_SCORE_ADJ_MAX.

To fix this, introduce a new oom_flags_t member in struct signal_struct
that will be used for per-thread oom killer flags.  KSM and swapoff can
now use a bit in this member to specify that threads should be killed
first in oom conditions without playing around with oom_score_adj.

This also allows the correct oom_score_adj to always be shown when reading
/proc/pid/oom_score.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: NMichal Hocko <mhocko@suse.cz>
Cc: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e1e12d2f
    • D
      mm, oom: change type of oom_score_adj to short · a9c58b90
      由 David Rientjes 提交于 
      The maximum oom_score_adj is 1000 and the minimum oom_score_adj is -1000,
so this range can be represented by the signed short type with no
functional change.  The extra space this frees up in struct signal_struct
will be used for per-thread oom kill flags in the next patch.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: NMichal Hocko <mhocko@suse.cz>
Cc: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a9c58b90
    • D
      mm, oom: allow exiting threads to have access to memory reserves · 9ff4868e
      由 David Rientjes 提交于 
      Exiting threads, those with PF_EXITING set, can pagefault and require
memory before they can make forward progress.  This happens, for instance,
when a process must fault task->robust_list, a userspace structure, before
detaching its memory.

These threads also aren't guaranteed to get access to memory reserves
unless oom killed or killed from userspace.  The oom killer won't grant
memory reserves if other threads are also exiting other than current and
stalling at the same point.  This prevents needlessly killing processes
when others are already exiting.

Instead of special casing all the possible situations between PF_EXITING
getting set and a thread detaching its mm where it may allocate memory,
which probably wouldn't get updated when a change is made to the exit
path, the solution is to give all exiting threads access to memory
reserves if they call the oom killer.  This allows them to quickly
allocate, detach its mm, and free the memory it represents.

Summary of Luigi's bug report:

: He had an oom condition where threads were faulting on task->robust_list
: and repeatedly called the oom killer but it would defer killing a thread
: because it saw other PF_EXITING threads.  This can happen anytime we need
: to allocate memory after setting PF_EXITING and before detaching our mm;
: if there are other threads in the same state then the oom killer won't do
: anything unless one of them happens to be killed from userspace.
:
: So instead of only deferring for PF_EXITING and !task->robust_list, it's
: better to just give them access to memory reserves to prevent a potential
: livelock so that any other faults that may be introduced in the future in
: the exit path don't cause the same problem (and hopefully we don't allow
: too many of those!).
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Tested-by: NLuigi Semenzato <semenzato@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      9ff4868e
  33. 09 10月, 2012 1 次提交
  35. 01 8月, 2012 8 次提交
  37. 21 6月, 2012 2 次提交
  39. 09 6月, 2012 1 次提交
  41. 30 5月, 2012 1 次提交
  43. 03 5月, 2012 1 次提交
  45. 24 3月, 2012 1 次提交
  47. 22 3月, 2012 1 次提交