[PATCH] oom, memcg: handle sysctl oom_kill_allocating_task while memcg oom happening

[Sha Zhengju <handai.szj@taobao.com>]

From: Sha Zhengju <handai.szj@taobao.com>

Sysctl oom_kill_allocating_task enables or disables killing the OOM-triggering
task in out-of-memory situations, but it only works on overall system-wide oom.
But it's also a useful indication in memcg so we take it into consideration
while oom happening in memcg. Other sysctl such as panic_on_oom has already
been memcg-ware.


Signed-off-by: Sha Zhengju <handai.szj@taobao.com>
---
 mm/oom_kill.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 38129e3..2a176af 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -574,6 +574,18 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask)
        check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0, NULL);
        limit = mem_cgroup_get_limit(memcg) >> PAGE_SHIFT;
        read_lock(&tasklist_lock);
+       if (sysctl_oom_kill_allocating_task &&
+           !oom_unkillable_task(current, memcg, NULL) &&
+           current->mm) {
+               /*
+                * oom_kill_process() needs tasklist_lock held.  If it returns
+                * non-zero, current could not be killed so we must fallback to
+                * the tasklist scan.
+                */
+               if (!oom_kill_process(current, gfp_mask, 0, 0, limit, memcg, NULL,
+                               "Memory cgroup out of memory (oom_kill_allocating_task)"))
+                       goto out;
+       }
 retry:
        p = select_bad_process(&points, limit, memcg, NULL);
        if (!p || PTR_ERR(p) == -1UL)
--
1.7.6.1


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