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authorTejun Heo <tj@kernel.org>2011-11-21 12:32:25 -0800
committerTejun Heo <tj@kernel.org>2011-11-21 12:32:25 -0800
commita3201227f803ad7fd43180c5195dbe5a2bf998aa (patch)
tree1845ba06346f8a8772fe1c90f8960bd1a430d05c /include
parent22b4e111fa01a1147aa562ceaf18a752a928ef4e (diff)
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freezer: make freezing() test freeze conditions in effect instead of TIF_FREEZE
Using TIF_FREEZE for freezing worked when there was only single freezing condition (the PM one); however, now there is also the cgroup_freezer and single bit flag is getting clumsy. thaw_processes() is already testing whether cgroup freezing in in effect to avoid thawing tasks which were frozen by both PM and cgroup freezers. This is racy (nothing prevents race against cgroup freezing) and fragile. A much simpler way is to test actual freeze conditions from freezing() - ie. directly test whether PM or cgroup freezing is in effect. This patch adds variables to indicate whether and what type of freezing conditions are in effect and reimplements freezing() such that it directly tests whether any of the two freezing conditions is active and the task should freeze. On fast path, freezing() is still very cheap - it only tests system_freezing_cnt. This makes the clumsy dancing aroung TIF_FREEZE unnecessary and freeze/thaw operations more usual - updating state variables for the new state and nudging target tasks so that they notice the new state and comply. As long as the nudging happens after state update, it's race-free. * This allows use of freezing() in freeze_task(). Replace the open coded tests with freezing(). * p != current test is added to warning printing conditions in try_to_freeze_tasks() failure path. This is necessary as freezing() is now true for the task which initiated freezing too. -v2: Oleg pointed out that re-freezing FROZEN cgroup could increment system_freezing_cnt. Fixed. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Paul Menage <paul@paulmenage.org> (for the cgroup portions)
Diffstat (limited to 'include')
-rw-r--r--include/linux/freezer.h33
1 files changed, 12 insertions, 21 deletions
diff --git a/include/linux/freezer.h b/include/linux/freezer.h
index b2b4abc5a739..8e29f2b7ce11 100644
--- a/include/linux/freezer.h
+++ b/include/linux/freezer.h
@@ -5,8 +5,13 @@
#include <linux/sched.h>
#include <linux/wait.h>
+#include <linux/atomic.h>
#ifdef CONFIG_FREEZER
+extern atomic_t system_freezing_cnt; /* nr of freezing conds in effect */
+extern bool pm_freezing; /* PM freezing in effect */
+extern bool pm_nosig_freezing; /* PM nosig freezing in effect */
+
/*
* Check if a process has been frozen
*/
@@ -15,28 +20,16 @@ static inline int frozen(struct task_struct *p)
return p->flags & PF_FROZEN;
}
-/*
- * Check if there is a request to freeze a process
- */
-static inline int freezing(struct task_struct *p)
-{
- return test_tsk_thread_flag(p, TIF_FREEZE);
-}
+extern bool freezing_slow_path(struct task_struct *p);
/*
- * Request that a process be frozen
- */
-static inline void set_freeze_flag(struct task_struct *p)
-{
- set_tsk_thread_flag(p, TIF_FREEZE);
-}
-
-/*
- * Sometimes we may need to cancel the previous 'freeze' request
+ * Check if there is a request to freeze a process
*/
-static inline void clear_freeze_flag(struct task_struct *p)
+static inline bool freezing(struct task_struct *p)
{
- clear_tsk_thread_flag(p, TIF_FREEZE);
+ if (likely(!atomic_read(&system_freezing_cnt)))
+ return false;
+ return freezing_slow_path(p);
}
static inline bool should_send_signal(struct task_struct *p)
@@ -174,9 +167,7 @@ static inline void set_freezable_with_signal(void)
})
#else /* !CONFIG_FREEZER */
static inline int frozen(struct task_struct *p) { return 0; }
-static inline int freezing(struct task_struct *p) { return 0; }
-static inline void set_freeze_flag(struct task_struct *p) {}
-static inline void clear_freeze_flag(struct task_struct *p) {}
+static inline bool freezing(struct task_struct *p) { return false; }
static inline bool __refrigerator(bool check_kthr_stop) { return false; }
static inline int freeze_processes(void) { return -ENOSYS; }