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authorPeter Zijlstra <peterz@infradead.org>2012-06-22 13:36:05 +0200
committerBen Hutchings <ben@decadent.org.uk>2012-08-10 00:11:14 +0100
commitb75bfc42974aaf089ae7eae5d3c6bf362f57ee93 (patch)
treefdccebf8528123755b151ae4d504a6bb3c286368 /include
parent46159f6e9d9a41a0ec1914f983e7ca6e416330c1 (diff)
sched: Fix race in task_group()
commit 8323f26ce3425460769605a6aece7a174edaa7d1 upstream Stefan reported a crash on a kernel before a3e5d1091c1 ("sched: Don't call task_group() too many times in set_task_rq()"), he found the reason to be that the multiple task_group() invocations in set_task_rq() returned different values. Looking at all that I found a lack of serialization and plain wrong comments. The below tries to fix it using an extra pointer which is updated under the appropriate scheduler locks. Its not pretty, but I can't really see another way given how all the cgroup stuff works. Reported-and-tested-by: Stefan Bader <stefan.bader@canonical.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1340364965.18025.71.camel@twins Signed-off-by: Ingo Molnar <mingo@kernel.org> (backported to previous file names and layout) Signed-off-by: Stefan Bader <stefan.bader@canonical.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'include')
-rw-r--r--include/linux/init_task.h12
-rw-r--r--include/linux/sched.h5
2 files changed, 15 insertions, 2 deletions
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index df53fdf5a304..cdde2b379c8d 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -124,8 +124,17 @@ extern struct group_info init_groups;
extern struct cred init_cred;
+extern struct task_group root_task_group;
+
+#ifdef CONFIG_CGROUP_SCHED
+# define INIT_CGROUP_SCHED(tsk) \
+ .sched_task_group = &root_task_group,
+#else
+# define INIT_CGROUP_SCHED(tsk)
+#endif
+
#ifdef CONFIG_PERF_EVENTS
-# define INIT_PERF_EVENTS(tsk) \
+# define INIT_PERF_EVENTS(tsk) \
.perf_event_mutex = \
__MUTEX_INITIALIZER(tsk.perf_event_mutex), \
.perf_event_list = LIST_HEAD_INIT(tsk.perf_event_list),
@@ -162,6 +171,7 @@ extern struct cred init_cred;
}, \
.tasks = LIST_HEAD_INIT(tsk.tasks), \
INIT_PUSHABLE_TASKS(tsk) \
+ INIT_CGROUP_SCHED(tsk) \
.ptraced = LIST_HEAD_INIT(tsk.ptraced), \
.ptrace_entry = LIST_HEAD_INIT(tsk.ptrace_entry), \
.real_parent = &tsk, \
diff --git a/include/linux/sched.h b/include/linux/sched.h
index d336c3596761..1e86bb421d28 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1236,6 +1236,9 @@ struct task_struct {
const struct sched_class *sched_class;
struct sched_entity se;
struct sched_rt_entity rt;
+#ifdef CONFIG_CGROUP_SCHED
+ struct task_group *sched_task_group;
+#endif
#ifdef CONFIG_PREEMPT_NOTIFIERS
/* list of struct preempt_notifier: */
@@ -2646,7 +2649,7 @@ extern int sched_group_set_rt_period(struct task_group *tg,
extern long sched_group_rt_period(struct task_group *tg);
extern int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk);
#endif
-#endif
+#endif /* CONFIG_CGROUP_SCHED */
extern int task_can_switch_user(struct user_struct *up,
struct task_struct *tsk);