From d02f52811d0eb8e2a14718d3bafded2106f8886c Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Sat, 20 Aug 2011 11:31:40 +0200 Subject: [PATCH] cgroup_freezer: prepare for removal of TIF_FREEZE TIF_FREEZE will be removed soon and freezing() will directly test whether any freezing condition is in effect. Make the following changes in preparation. * Rename cgroup_freezing_or_frozen() to cgroup_freezing() and make it return bool. * Make cgroup_freezing() access task_freezer() under rcu read lock instead of task_lock(). This makes the state dereferencing racy against task moving to another cgroup; however, it was already racy without this change as ->state dereference wasn't synchronized. This will be later dealt with using attach hooks. * freezer->state is now set before trying to push tasks into the target state. Signed-off-by: Tejun Heo Acked-by: Paul Menage Cc: Li Zefan --- include/linux/freezer.h | 6 +++--- kernel/cgroup_freezer.c | 36 ++++++++++++------------------------ kernel/power/process.c | 2 +- 3 files changed, 16 insertions(+), 28 deletions(-) diff --git a/include/linux/freezer.h b/include/linux/freezer.h index 13559a808098..bcc0637f478c 100644 --- a/include/linux/freezer.h +++ b/include/linux/freezer.h @@ -63,11 +63,11 @@ extern bool freeze_task(struct task_struct *p, bool sig_only); extern bool __set_freezable(bool with_signal); #ifdef CONFIG_CGROUP_FREEZER -extern int cgroup_freezing_or_frozen(struct task_struct *task); +extern bool cgroup_freezing(struct task_struct *task); #else /* !CONFIG_CGROUP_FREEZER */ -static inline int cgroup_freezing_or_frozen(struct task_struct *task) +static inline bool cgroup_freezing(struct task_struct *task) { - return 0; + return false; } #endif /* !CONFIG_CGROUP_FREEZER */ diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c index e7fa0ec0690e..0478c354cb21 100644 --- a/kernel/cgroup_freezer.c +++ b/kernel/cgroup_freezer.c @@ -48,19 +48,17 @@ static inline struct freezer *task_freezer(struct task_struct *task) struct freezer, css); } -static inline int __cgroup_freezing_or_frozen(struct task_struct *task) +bool cgroup_freezing(struct task_struct *task) { - enum freezer_state state = task_freezer(task)->state; - return (state == CGROUP_FREEZING) || (state == CGROUP_FROZEN); -} + enum freezer_state state; + bool ret; -int cgroup_freezing_or_frozen(struct task_struct *task) -{ - int result; - task_lock(task); - result = __cgroup_freezing_or_frozen(task); - task_unlock(task); - return result; + rcu_read_lock(); + state = task_freezer(task)->state; + ret = state == CGROUP_FREEZING || state == CGROUP_FROZEN; + rcu_read_unlock(); + + return ret; } /* @@ -102,9 +100,6 @@ struct cgroup_subsys freezer_subsys; * freezer_can_attach(): * cgroup_mutex (held by caller of can_attach) * - * cgroup_freezing_or_frozen(): - * task->alloc_lock (to get task's cgroup) - * * freezer_fork() (preserving fork() performance means can't take cgroup_mutex): * freezer->lock * sighand->siglock (if the cgroup is freezing) @@ -177,13 +172,7 @@ static int freezer_can_attach(struct cgroup_subsys *ss, static int freezer_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk) { - rcu_read_lock(); - if (__cgroup_freezing_or_frozen(tsk)) { - rcu_read_unlock(); - return -EBUSY; - } - rcu_read_unlock(); - return 0; + return cgroup_freezing(tsk) ? -EBUSY : 0; } static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task) @@ -279,7 +268,6 @@ static int try_to_freeze_cgroup(struct cgroup *cgroup, struct freezer *freezer) struct task_struct *task; unsigned int num_cant_freeze_now = 0; - freezer->state = CGROUP_FREEZING; cgroup_iter_start(cgroup, &it); while ((task = cgroup_iter_next(cgroup, &it))) { if (!freeze_task(task, true)) @@ -303,8 +291,6 @@ static void unfreeze_cgroup(struct cgroup *cgroup, struct freezer *freezer) while ((task = cgroup_iter_next(cgroup, &it))) __thaw_task(task); cgroup_iter_end(cgroup, &it); - - freezer->state = CGROUP_THAWED; } static int freezer_change_state(struct cgroup *cgroup, @@ -321,6 +307,8 @@ static int freezer_change_state(struct cgroup *cgroup, if (goal_state == freezer->state) goto out; + freezer->state = goal_state; + switch (goal_state) { case CGROUP_THAWED: unfreeze_cgroup(cgroup, freezer); diff --git a/kernel/power/process.c b/kernel/power/process.c index f8012f2f5cdf..1bbc363df4a9 100644 --- a/kernel/power/process.c +++ b/kernel/power/process.c @@ -154,7 +154,7 @@ void thaw_processes(void) read_lock(&tasklist_lock); do_each_thread(g, p) { - if (cgroup_freezing_or_frozen(p)) + if (cgroup_freezing(p)) continue; __thaw_task(p); -- 2.39.5