Manish Jaggi noticed that running LTP oom01/oom02 ltp tests with high core
count causes random kernel panics when an OOM victim which consumed memory
in a way the OOM reaper does not help was selected by the OOM killer.
----------
oom02 0 TINFO : start OOM testing for mlocked pages.
oom02 0 TINFO : expected victim is 4578.
oom02 0 TINFO : thread (ffff8b0e71f0), allocating 3221225472 bytes.
oom02 0 TINFO : thread (ffff8b8e71f0), allocating 3221225472 bytes.
(...snipped...)
oom02 0 TINFO : thread (ffff8a0e71f0), allocating 3221225472 bytes.
[ 364.737486] oom02:4583 invoked oom-killer: gfp_mask=0x16080c0(GFP_KERNEL|__GFP_ZERO|__GFP_NOTRACK), nodemask=1, order=0, oom_score_adj=0
(...snipped...)
[ 365.036127] [ pid ] uid tgid total_vm rss nr_ptes nr_pmds swapents oom_score_adj name
[ 365.044691] [ 1905] 0 1905 3236 1714 10 4 0 0 systemd-journal
[ 365.054172] [ 1908] 0 1908 20247 590 8 4 0 0 lvmetad
[ 365.062959] [ 2421] 0 2421 3241 878 9 3 0 -1000 systemd-udevd
[ 365.072266] [ 3125] 0 3125 3834 719 9 4 0 -1000 auditd
[ 365.080963] [ 3145] 0 3145 1086 630 6 4 0 0 systemd-logind
[ 365.090353] [ 3146] 0 3146 1208 596 7 3 0 0 irqbalance
[ 365.099413] [ 3147] 81 3147 1118 625 5 4 0 -900 dbus-daemon
[ 365.108548] [ 3149] 998 3149 116294 4180 26 5 0 0 polkitd
[ 365.117333] [ 3164] 997 3164 19992 785 9 3 0 0 chronyd
[ 365.126118] [ 3180] 0 3180 55605 7880 29 3 0 0 firewalld
[ 365.135075] [ 3187] 0 3187 87842 3033 26 3 0 0 NetworkManager
[ 365.144465] [ 3290] 0 3290 43037 1224 16 5 0 0 rsyslogd
[ 365.153335] [ 3295] 0 3295 108279 6617 30 3 0 0 tuned
[ 365.161944] [ 3308] 0 3308 27846 676 11 3 0 0 crond
[ 365.170554] [ 3309] 0 3309 3332 616 10 3 0 -1000 sshd
[ 365.179076] [ 3371] 0 3371 27307 364 6 3 0 0 agetty
[ 365.187790] [ 3375] 0 3375 29397 1125 11 3 0 0 login
[ 365.196402] [ 4178] 0 4178 4797 1119 14 4 0 0 master
[ 365.205101] [ 4209] 89 4209 4823 1396 12 4 0 0 pickup
[ 365.213798] [ 4211] 89 4211 4842 1485 12 3 0 0 qmgr
[ 365.222325] [ 4491] 0 4491 27965 1022 8 3 0 0 bash
[ 365.230849] [ 4513] 0 4513 670 365 5 3 0 0 oom02
[ 365.239459] [ 4578] 0 4578 37776030 32890957 64257 138 0 0 oom02
[ 365.248067] Out of memory: Kill process 4578 (oom02) score 952 or sacrifice child
[ 365.255581] Killed process 4578 (oom02) total-vm:151104120kB, anon-rss:131562528kB, file-rss:1300kB, shmem-rss:0kB
[ 365.266829] out_of_memory: Current (4583) has a pending SIGKILL
[ 365.267347] oom_reaper: reaped process 4578 (oom02), now anon-rss:131559616kB, file-rss:0kB, shmem-rss:0kB
[ 365.282658] oom_reaper: reaped process 4583 (oom02), now anon-rss:131561664kB, file-rss:0kB, shmem-rss:0kB
[ 365.283361] oom02:4586 invoked oom-killer: gfp_mask=0x16040c0(GFP_KERNEL|__GFP_COMP|__GFP_NOTRACK), nodemask=1, order=0, oom_score_adj=0
(...snipped...)
[ 365.576164] oom02:4585 invoked oom-killer: gfp_mask=0x16080c0(GFP_KERNEL|__GFP_ZERO|__GFP_NOTRACK), nodemask=1, order=0, oom_score_adj=0
(...snipped...)
[ 365.576298] [ pid ] uid tgid total_vm rss nr_ptes nr_pmds swapents oom_score_adj name
[ 365.576338] [ 2421] 0 2421 3241 878 9 3 0 -1000 systemd-udevd
[ 365.576342] [ 3125] 0 3125 3834 719 9 4 0 -1000 auditd
[ 365.576347] [ 3309] 0 3309 3332 616 10 3 0 -1000 sshd
[ 365.576356] [ 4580] 0 4578 37776030 32890417 64258 138 0 0 oom02
[ 365.576361] Kernel panic - not syncing: Out of memory and no killable processes...
----------
Since commit 696453e66630ad45 ("mm, oom: task_will_free_mem should skip
oom_reaped tasks") changed task_will_free_mem(current) in out_of_memory()
to return false as soon as MMF_OOM_SKIP is set, many threads sharing
the victim's mm were not able to try allocation from memory reserves
after the OOM reaper gave up reclaiming memory.
We don't need to give up task_will_free_mem(current) without trying
allocation from memory reserves. We will need to select next OOM victim
only when allocation from memory reserves did not help.
Thus, this patch allows task_will_free_mem(current) to ignore MMF_OOM_SKIP
for once so that task_will_free_mem(current) will not start selecting next
OOM victim without trying allocation from memory reserves.
Link: http://lkml.kernel.org/r/e6c83a26-1d59-4afd-55cf-04e58bdde188@xxxxxxxxxxxxxxxxxx
Reported-by: Manish Jaggi <mjaggi@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Fixes: 696453e66630ad45 ("mm, oom: task_will_free_mem should skip oom_reaped tasks")
---
include/linux/sched.h | 1 +
mm/oom_kill.c | 14 +++++++++++---
2 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 94137e7..88da211 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -652,6 +652,7 @@ struct task_struct {
/* disallow userland-initiated cgroup migration */
unsigned no_cgroup_migration:1;
#endif
+ unsigned oom_kill_free_check_raced:1;
unsigned long atomic_flags; /* Flags requiring atomic access. */
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 9e8b4f0..a1ae78d 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -780,11 +780,19 @@ static bool task_will_free_mem(struct task_struct *task)
return false;
/*
- * This task has already been drained by the oom reaper so there are
- * only small chances it will free some more
+ * It is possible that current thread fails to try allocation from
+ * memory reserves if the OOM reaper set MMF_OOM_SKIP on this mm before
+ * current thread calls out_of_memory() in order to get TIF_MEMDIE.
+ * In that case, allow current thread to try TIF_MEMDIE allocation
+ * before start selecting next OOM victims.
*/
- if (test_bit(MMF_OOM_SKIP, &mm->flags))
+ if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
+ if (task == current && !task->oom_kill_free_check_raced) {
+ task->oom_kill_free_check_raced = true;
+ return true;
+ }
return false;
+ }
if (atomic_read(&mm->mm_users) <= 1)
return true;
--
1.8.3.1
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