Hello, On (05/13/15 16:35), Tejun Heo wrote: [..] > -static inline void threadgroup_lock(struct task_struct *tsk) > +static inline void threadgroup_change_begin(struct task_struct *tsk) > { > - down_write(&tsk->signal->group_rwsem); > + might_sleep(); I think cgroup_threadgroup_change_begin()->down_read() already does might_sleep() check. -ss > + cgroup_threadgroup_change_begin(tsk); > } > > /** > - * threadgroup_unlock - unlock threadgroup > - * @tsk: member task of the threadgroup to unlock > + * threadgroup_change_end - mark the end of changes to a threadgroup > + * @tsk: task causing the changes > * > - * Reverse threadgroup_lock(). > + * See threadgroup_change_begin(). > */ > -static inline void threadgroup_unlock(struct task_struct *tsk) > +static inline void threadgroup_change_end(struct task_struct *tsk) > { > - up_write(&tsk->signal->group_rwsem); > + cgroup_threadgroup_change_end(tsk); > } > -#else > -static inline void threadgroup_change_begin(struct task_struct *tsk) {} > -static inline void threadgroup_change_end(struct task_struct *tsk) {} > -static inline void threadgroup_lock(struct task_struct *tsk) {} > -static inline void threadgroup_unlock(struct task_struct *tsk) {} > -#endif > > #ifndef __HAVE_THREAD_FUNCTIONS > > diff --git a/kernel/cgroup.c b/kernel/cgroup.c > index cfa27f9..9309452 100644 > --- a/kernel/cgroup.c > +++ b/kernel/cgroup.c > @@ -848,6 +848,48 @@ static struct css_set *find_css_set(struct css_set *old_cset, > return cset; > } > > +void cgroup_threadgroup_change_begin(struct task_struct *tsk) > +{ > + down_read(&tsk->signal->group_rwsem); > +} > + > +void cgroup_threadgroup_change_end(struct task_struct *tsk) > +{ > + up_read(&tsk->signal->group_rwsem); > +} > + > +/** > + * threadgroup_lock - lock threadgroup > + * @tsk: member task of the threadgroup to lock > + * > + * Lock the threadgroup @tsk belongs to. No new task is allowed to enter > + * and member tasks aren't allowed to exit (as indicated by PF_EXITING) or > + * change ->group_leader/pid. This is useful for cases where the threadgroup > + * needs to stay stable across blockable operations. > + * > + * fork and exit explicitly call threadgroup_change_{begin|end}() for > + * synchronization. While held, no new task will be added to threadgroup > + * and no existing live task will have its PF_EXITING set. > + * > + * de_thread() does threadgroup_change_{begin|end}() when a non-leader > + * sub-thread becomes a new leader. > + */ > +static void threadgroup_lock(struct task_struct *tsk) > +{ > + down_write(&tsk->signal->group_rwsem); > +} > + > +/** > + * threadgroup_unlock - unlock threadgroup > + * @tsk: member task of the threadgroup to unlock > + * > + * Reverse threadgroup_lock(). > + */ > +static inline void threadgroup_unlock(struct task_struct *tsk) > +{ > + up_write(&tsk->signal->group_rwsem); > +} > + > static struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root) > { > struct cgroup *root_cgrp = kf_root->kn->priv; > -- > 2.1.0 > > -- > To unsubscribe from this list: send the line "unsubscribe cgroups" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html