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Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

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* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  rcu: Fix RCU lockdep splat on freezer_fork path
  rcu: Fix RCU lockdep splat in set_task_cpu on fork path
  mutex: Don't spin when the owner CPU is offline or other weird cases
This commit is contained in:
Linus Torvalds 2010-05-04 15:15:43 -07:00
commit f2809d61d6
2 changed files with 18 additions and 5 deletions
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5
kernel/cgroup_freezer.c
View file

@ -205,9 +205,12 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
* No lock is needed, since the task isn't on tasklist yet,
* so it can't be moved to another cgroup, which means the
* freezer won't be removed and will be valid during this
* function call.
* function call. Nevertheless, apply RCU read-side critical
* section to suppress RCU lockdep false positives.
*/
rcu_read_lock();
freezer = task_freezer(task);
rcu_read_unlock();
/*
* The root cgroup is non-freezable, so we can skip the

18
kernel/sched.c
View file

@ -323,6 +323,15 @@ static inline struct task_group *task_group(struct task_struct *p)
/* Change a task's cfs_rq and parent entity if it moves across CPUs/groups */
static inline void set_task_rq(struct task_struct *p, unsigned int cpu)
{
/*
* Strictly speaking this rcu_read_lock() is not needed since the
* task_group is tied to the cgroup, which in turn can never go away
* as long as there are tasks attached to it.
*
* However since task_group() uses task_subsys_state() which is an
* rcu_dereference() user, this quiets CONFIG_PROVE_RCU.
*/
rcu_read_lock();
#ifdef CONFIG_FAIR_GROUP_SCHED
p->se.cfs_rq = task_group(p)->cfs_rq[cpu];
p->se.parent = task_group(p)->se[cpu];
@ -332,6 +341,7 @@ static inline void set_task_rq(struct task_struct *p, unsigned int cpu)
p->rt.rt_rq = task_group(p)->rt_rq[cpu];
p->rt.parent = task_group(p)->rt_se[cpu];
#endif
rcu_read_unlock();
}
#else
@ -3780,7 +3790,7 @@ int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner)
* the mutex owner just released it and exited.
*/
if (probe_kernel_address(&owner->cpu, cpu))
goto out;
return 0;
#else
cpu = owner->cpu;
#endif
@ -3790,14 +3800,14 @@ int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner)
* the cpu field may no longer be valid.
*/
if (cpu >= nr_cpumask_bits)
goto out;
return 0;
/*
* We need to validate that we can do a
* get_cpu() and that we have the percpu area.
*/
if (!cpu_online(cpu))
goto out;
return 0;
rq = cpu_rq(cpu);
@ -3816,7 +3826,7 @@ int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner)
cpu_relax();
}
out:
return 1;
}
#endif