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Commit dba091b9 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
Browse files

sched: Protect sched_rr_get_param() access to task->sched_class 



sched_rr_get_param calls
task->sched_class->get_rr_interval(task) without protection
against a concurrent sched_setscheduler() call which modifies
task->sched_class.

Serialize the access with task_rq_lock(task) and hand the rq
pointer into get_rr_interval() as it's needed at least in the
sched_fair implementation.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
LKML-Reference: <alpine.LFD.2.00.0912090930120.3089@localhost.localdomain>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 31605683

include/linux/sched.h

+2 −1
Original line number Diff line number Diff line
@@ -1111,7 +1111,8 @@ struct sched_class { 
	void (*prio_changed) (struct rq *this_rq, struct task_struct *task,

			     int oldprio, int running);



	unsigned int (*get_rr_interval) (struct task_struct *task);

	unsigned int (*get_rr_interval) (struct rq *rq,

					 struct task_struct *task);



#ifdef CONFIG_FAIR_GROUP_SCHED

	void (*moved_group) (struct task_struct *p);

kernel/sched.c

+5 −1
Original line number Diff line number Diff line
@@ -6887,6 +6887,8 @@ SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid, 
{

	struct task_struct *p;

	unsigned int time_slice;

	unsigned long flags;

	struct rq *rq;

	int retval;

	struct timespec t;
@@ -6903,7 +6905,9 @@ SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid, 
	if (retval)

		goto out_unlock;



	time_slice = p->sched_class->get_rr_interval(p);

	rq = task_rq_lock(p, &flags);

	time_slice = p->sched_class->get_rr_interval(rq, p);

	task_rq_unlock(rq, &flags);



	read_unlock(&tasklist_lock);

	jiffies_to_timespec(time_slice, &t);

kernel/sched_fair.c

+1 −5
Original line number Diff line number Diff line
@@ -2014,21 +2014,17 @@ static void moved_group_fair(struct task_struct *p) 
}

#endif



unsigned int get_rr_interval_fair(struct task_struct *task)

unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)

{

	struct sched_entity *se = &task->se;

	unsigned long flags;

	struct rq *rq;

	unsigned int rr_interval = 0;



	/*

	 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise

	 * idle runqueue:

	 */

	rq = task_rq_lock(task, &flags);

	if (rq->cfs.load.weight)

		rr_interval = NS_TO_JIFFIES(sched_slice(&rq->cfs, se));

	task_rq_unlock(rq, &flags);



	return rr_interval;

}

kernel/sched_idletask.c

+1 −1
Original line number Diff line number Diff line
@@ -97,7 +97,7 @@ static void prio_changed_idle(struct rq *rq, struct task_struct *p, 
		check_preempt_curr(rq, p, 0);

}



unsigned int get_rr_interval_idle(struct task_struct *task)

unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)

{

	return 0;

}

kernel/sched_rt.c

+1 −1
Original line number Diff line number Diff line
@@ -1721,7 +1721,7 @@ static void set_curr_task_rt(struct rq *rq) 
	dequeue_pushable_task(rq, p);

}



unsigned int get_rr_interval_rt(struct task_struct *task)

unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)

{

	/*

	 * Time slice is 0 for SCHED_FIFO tasks