On Wed 04-12-13 14:04:20, Oleg Nesterov wrote: > find_lock_task_mm() expects it is called under rcu or tasklist lock, > but it seems that at least oom_unkillable_task()->task_in_mem_cgroup() > and mem_cgroup_out_of_memory()->oom_badness() can call it lockless. > > Perhaps we could fix the callers, but this patch simply adds rcu lock > into find_lock_task_mm(). This also allows to simplify a bit one of its > callers, oom_kill_process(). > > Signed-off-by: Oleg Nesterov <[email protected]>
Reviewed-by: Michal Hocko <[email protected]> Thanks! > --- > mm/oom_kill.c | 12 ++++++++---- > 1 files changed, 8 insertions(+), 4 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 0d8ad1e..054ff47 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -102,14 +102,19 @@ struct task_struct *find_lock_task_mm(struct > task_struct *p) > { > struct task_struct *t; > > + rcu_read_lock(); > + > for_each_thread(p, t) { > task_lock(t); > if (likely(t->mm)) > - return t; > + goto found; > task_unlock(t); > } > + t = NULL; > +found: > + rcu_read_unlock(); > > - return NULL; > + return t; > } > > /* return true if the task is not adequate as candidate victim task. */ > @@ -461,10 +466,8 @@ void oom_kill_process(struct task_struct *p, gfp_t > gfp_mask, int order, > } > read_unlock(&tasklist_lock); > > - rcu_read_lock(); > p = find_lock_task_mm(victim); > if (!p) { > - rcu_read_unlock(); > put_task_struct(victim); > return; > } else if (victim != p) { > @@ -490,6 +493,7 @@ void oom_kill_process(struct task_struct *p, gfp_t > gfp_mask, int order, > * That thread will now get access to memory reserves since it has a > * pending fatal signal. > */ > + rcu_read_lock(); > for_each_process(p) > if (p->mm == mm && !same_thread_group(p, victim) && > !(p->flags & PF_KTHREAD)) { > -- > 1.5.5.1 > -- Michal Hocko SUSE Labs -- 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/
