mm, oom: remove task_lock protecting comm printing
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 <rientjes@google.com> Suggested-by: Oleg Nesterov <oleg@redhat.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -93,7 +93,7 @@ extern int current_cpuset_is_being_rebound(void);
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extern void rebuild_sched_domains(void);
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extern void cpuset_print_task_mems_allowed(struct task_struct *p);
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extern void cpuset_print_current_mems_allowed(void);
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/*
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* read_mems_allowed_begin is required when making decisions involving
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@ -219,7 +219,7 @@ static inline void rebuild_sched_domains(void)
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partition_sched_domains(1, NULL, NULL);
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}
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static inline void cpuset_print_task_mems_allowed(struct task_struct *p)
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static inline void cpuset_print_current_mems_allowed(void)
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{
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}
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@ -2598,22 +2598,22 @@ int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
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}
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/**
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* cpuset_print_task_mems_allowed - prints task's cpuset and mems_allowed
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* @tsk: pointer to task_struct of some task.
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* cpuset_print_current_mems_allowed - prints current's cpuset and mems_allowed
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*
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* Description: Prints @task's name, cpuset name, and cached copy of its
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* Description: Prints current's name, cpuset name, and cached copy of its
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* mems_allowed to the kernel log.
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*/
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void cpuset_print_task_mems_allowed(struct task_struct *tsk)
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void cpuset_print_current_mems_allowed(void)
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{
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struct cgroup *cgrp;
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rcu_read_lock();
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cgrp = task_cs(tsk)->css.cgroup;
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pr_info("%s cpuset=", tsk->comm);
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cgrp = task_cs(current)->css.cgroup;
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pr_info("%s cpuset=", current->comm);
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pr_cont_cgroup_name(cgrp);
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pr_cont(" mems_allowed=%*pbl\n", nodemask_pr_args(&tsk->mems_allowed));
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pr_cont(" mems_allowed=%*pbl\n",
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nodemask_pr_args(¤t->mems_allowed));
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rcu_read_unlock();
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}
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@ -377,13 +377,11 @@ static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask)
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static void dump_header(struct oom_control *oc, struct task_struct *p,
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struct mem_cgroup *memcg)
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{
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task_lock(current);
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pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
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"oom_score_adj=%hd\n",
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current->comm, oc->gfp_mask, oc->order,
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current->signal->oom_score_adj);
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cpuset_print_task_mems_allowed(current);
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task_unlock(current);
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cpuset_print_current_mems_allowed();
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dump_stack();
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if (memcg)
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mem_cgroup_print_oom_info(memcg, p);
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@ -509,10 +507,8 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
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if (__ratelimit(&oom_rs))
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dump_header(oc, p, memcg);
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task_lock(p);
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pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n",
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message, task_pid_nr(p), p->comm, points);
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task_unlock(p);
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/*
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* If any of p's children has a different mm and is eligible for kill,
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@ -586,10 +582,8 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
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if (fatal_signal_pending(p))
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continue;
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task_lock(p); /* Protect ->comm from prctl() */
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pr_info("Kill process %d (%s) sharing same memory\n",
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task_pid_nr(p), p->comm);
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task_unlock(p);
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do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
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}
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rcu_read_unlock();
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