On 02/14, Davidlohr Bueso wrote: > > On Mon, 2015-02-02 at 15:05 +0100, Oleg Nesterov wrote: > > --- a/kernel/futex.c > > +++ b/kernel/futex.c > > @@ -900,7 +900,7 @@ static int attach_to_pi_owner(u32 uval, union futex_key > > *key, > > if (!p) > > return -ESRCH; > > > > - if (!p->mm) { > > + if (unlikely(p->flags & PF_KTHREAD)) { > > put_task_struct(p); > > return -EPERM; > > } > > Futexes aren't the only naughty checkers,
Yes, this is the common mistake, > a quick search shows that, at > least, the oom killer and proc have this same problem. oom looks fine, note the PF_KTHREAD check in oom_unkillable(). It check ->mm for another reason, to figure out if this task has passed exit_mm() or not. proc looks fine too at first glance... we do not care if this mm was adopted via use_mm() or not. > Should we make > this generic and update accordingly? ie: > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 8db31ef..b0d37d6 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1991,6 +1991,11 @@ extern void thread_group_cputime_adjusted(struct > task_struct *p, cputime_t *ut, > #define tsk_used_math(p) ((p)->flags & PF_USED_MATH) > #define used_math() tsk_used_math(current) > > +static inline bool task_is_kthread(struct task_struct *task) > +{ > + return task->flags & PF_KTHREAD; > +} Perhaps... but PF_KTHREAD looks self-documented too ;) Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/