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> --- 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); } -- 2.10.2 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
