From 64ac72f81b1b41819dab596d1524bd5cae4813fd Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 22 Jun 2012 13:36:05 +0200 Subject: 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 Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1340364965.18025.71.camel@twins Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- include/linux/init_task.h | 12 +++++++++++- include/linux/sched.h | 5 ++++- 2 files changed, 15 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/init_task.h b/include/linux/init_task.h index 5e41a8e..921336f 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), @@ -160,6 +169,7 @@ 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 443ec43..0dae42e7 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1235,6 +1235,9 @@ 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: */ @@ -2613,7 +2616,7 @@ 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); -- cgit v1.1