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mm, oom: remove task_lock protecting comm printing

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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>
This commit is contained in:
David Rientjes
2015-11-05 18:48:05 -08:00
committed by Linus Torvalds
parent 2d1e10412c
commit da39da3a54
3 changed files with 10 additions and 16 deletions
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kernel/cpuset.c
+7 -7
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@@ -2598,22 +2598,22 @@ 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(&current->mems_allowed));
rcu_read_unlock();
}