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. Suggested-by: Oleg Nesterov <[email protected]> Signed-off-by: David Rientjes <[email protected]> --- include/linux/cpuset.h | 4 ++-- kernel/cpuset.c | 14 +++++++------- mm/oom_kill.c | 8 +------- 3 files changed, 10 insertions(+), 16 deletions(-) diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -93,7 +93,7 @@ extern int current_cpuset_is_being_rebound(void); extern void rebuild_sched_domains(void); -extern void cpuset_print_task_mems_allowed(struct task_struct *p); +extern void cpuset_print_current_mems_allowed(void); /* * read_mems_allowed_begin is required when making decisions involving @@ -219,7 +219,7 @@ static inline void rebuild_sched_domains(void) partition_sched_domains(1, NULL, NULL); } -static inline void cpuset_print_task_mems_allowed(struct task_struct *p) +static inline void cpuset_print_current_mems_allowed(void) { } diff --git a/kernel/cpuset.c b/kernel/cpuset.c --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -2599,22 +2599,22 @@ int cpuset_mems_allowed_intersects(const struct task_struct *tsk1, } /** - * cpuset_print_task_mems_allowed - prints task's cpuset and mems_allowed - * @tsk: pointer to task_struct of some task. + * cpuset_print_current_mems_allowed - prints current's cpuset and mems_allowed * - * Description: Prints @task's name, cpuset name, and cached copy of its + * Description: Prints current's name, cpuset name, and cached copy of its * mems_allowed to the kernel log. */ -void cpuset_print_task_mems_allowed(struct task_struct *tsk) +void cpuset_print_current_mems_allowed(void) { struct cgroup *cgrp; rcu_read_lock(); - cgrp = task_cs(tsk)->css.cgroup; - pr_info("%s cpuset=", tsk->comm); + cgrp = task_cs(current)->css.cgroup; + pr_info("%s cpuset=", current->comm); pr_cont_cgroup_name(cgrp); - pr_cont(" mems_allowed=%*pbl\n", nodemask_pr_args(&tsk->mems_allowed)); + pr_cont(" mems_allowed=%*pbl\n", + nodemask_pr_args(¤t->mems_allowed)); rcu_read_unlock(); } diff --git a/mm/oom_kill.c b/mm/oom_kill.c --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -386,13 +386,11 @@ static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask) static void dump_header(struct oom_control *oc, struct task_struct *p, struct mem_cgroup *memcg) { - task_lock(current); pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, " "oom_score_adj=%hd\n", current->comm, oc->gfp_mask, oc->order, current->signal->oom_score_adj); - cpuset_print_task_mems_allowed(current); - task_unlock(current); + cpuset_print_current_mems_allowed(); dump_stack(); if (memcg) mem_cgroup_print_oom_info(memcg, p); @@ -518,10 +516,8 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p, if (__ratelimit(&oom_rs)) dump_header(oc, p, memcg); - task_lock(p); pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n", message, task_pid_nr(p), p->comm, points); - task_unlock(p); /* * If any of p's children has a different mm and is eligible for kill, @@ -586,10 +582,8 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p, if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) continue; - task_lock(p); /* Protect ->comm from prctl() */ pr_err("Kill process %d (%s) sharing same memory\n", task_pid_nr(p), p->comm); - task_unlock(p); do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true); } rcu_read_unlock(); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
