Messages in this thread | | | Subject | Re: [patch 2/2] sched: Protect sched_rr_get_param access to task->sched_class | From | Peter Zijlstra <> | Date | Wed, 09 Dec 2009 09:03:18 +0100 |
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On Wed, 2009-12-09 at 09:00 +0100, Peter Zijlstra wrote: > On Tue, 2009-12-08 at 20:24 +0000, Thomas Gleixner wrote: > > plain text document attachment > > (sched-fix-sched-get-rr-param-race.patch) > > 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); > > > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > > --- > > kernel/sched.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > Index: linux-2.6-tip/kernel/sched.c > > =================================================================== > > --- linux-2.6-tip.orig/kernel/sched.c > > +++ linux-2.6-tip/kernel/sched.c > > @@ -6887,6 +6887,8 @@ SYSCALL_DEFINE2(sched_rr_get_interval, p > > { > > 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, p > > if (retval) > > goto out_unlock; > > > > + rq = task_rq_lock(p, &flags); > > time_slice = p->sched_class->get_rr_interval(p); > > + task_rq_unlock(rq, &flags); > > > > read_unlock(&tasklist_lock); > > jiffies_to_timespec(time_slice, &t); > > > > Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Oh, that was too quick, get_rr_interval_fair() actually takes the rq->lock, so lets add this:
unsigned int get_rr_interval_fair(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; }
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