On 12/19/2016 06:54 PM, Andrey Ryabinin wrote:
From: David Rientjes <rient...@google.com>
ML: da39da3a54fed88e29024f2f1f6cd7357cd03a44
The oom killer takes task_lock() in a couple of places solely to protect
printing the task's comm.
A process's comm, including current's comm, may change due to
/proc/pid/comm or PR_SET_NAME.
The comm will always be NULL-terminated, so the worst race scenario would
only be during update. We can tolerate a comm being printed that is in
the middle of an update to avoid taking the lock.
Other locations in the kernel have already dropped task_lock() when
printing comm, so this is consistent.
Signed-off-by: David Rientjes <rient...@google.com>
Suggested-by: Oleg Nesterov <o...@redhat.com>
Cc: Michal Hocko <mho...@kernel.org>
Cc: Vladimir Davydov <vdavy...@parallels.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.w...@gmail.com>
Acked-by: Johannes Weiner <han...@cmpxchg.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
https://jira.sw.ru/browse/PSBM-56178
[Partial backport - this patch doesn't contain changes in kernel/cpuset.c
from the upstream patch. Our kernel still needs task_lock() task lock there
to protect task_cs(). Upstream switched to RCU protection thus it doesn't
need task_lock() to protect task_cs()]
Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
Thanks,
Reviewed-by: Dmitry Safonov <dsafo...@virtuozzo.com>
---
mm/oom_kill.c | 11 +----------
1 file changed, 1 insertion(+), 10 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index f9a8e62..59b109e 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -570,10 +570,8 @@ bool oom_trylock(struct mem_cgroup *memcg)
struct task_struct *p = ctx->victim;
if (p && ctx->marked) {
- task_lock(p);
pr_err("OOM kill timeout: %d (%s)\n",
task_pid_nr(p), p->comm);
- task_unlock(p);
show_stack(p, NULL);
}
@@ -766,12 +764,9 @@ static void oom_berserker(unsigned long points, unsigned
long overdraft,
points * 100 / totalpages)
continue;
- if (__ratelimit(&berserker_rs)) {
- task_lock(p);
+ if (__ratelimit(&berserker_rs))
pr_err("Rage kill process %d (%s)\n",
task_pid_nr(p), p->comm);
- task_unlock(p);
- }
do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
mem_cgroup_note_oom_kill(memcg, p);
@@ -818,10 +813,8 @@ void oom_kill_process(struct task_struct *p, gfp_t
gfp_mask, int order,
if (__ratelimit(&oom_rs))
dump_header(p, gfp_mask, order, memcg, nodemask);
- task_lock(p);
pr_err("%s: Kill process %d (%s) score %lu or sacrifice child\n",
message, task_pid_nr(p), p->comm, points * 1000 / totalpages);
- task_unlock(p);
/*
* If any of p's children has a different mm and is eligible for kill,
@@ -891,10 +884,8 @@ void oom_kill_process(struct task_struct *p, gfp_t
gfp_mask, int order,
if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
continue;
- task_lock(p); /* Protect ->comm from prctl() */
pr_err("Kill process %d (%s) in VE \"%s\" sharing same
memory\n",
task_pid_nr(p), p->comm, task_ve_name(p));
- task_unlock(p);
do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
mem_cgroup_note_oom_kill(memcg, p);
}
--
Dmitry
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