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

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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: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <alpine.LFD.2.00.0912090930120.3089@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Thomas Gleixner 2009-12-09 09:32:03 +01:00 committed by Ingo Molnar
parent 3160568371
commit dba091b9e3
5 changed files with 10 additions and 9 deletions
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3
include/linux/sched.h
View file

@ -1111,7 +1111,8 @@ struct sched_class {
void (*prio_changed) (struct rq *this_rq, struct task_struct *task, void (*prio_changed) (struct rq *this_rq, struct task_struct *task,
int oldprio, int running); 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 #ifdef CONFIG_FAIR_GROUP_SCHED
void (*moved_group) (struct task_struct *p); void (*moved_group) (struct task_struct *p);

6
kernel/sched.c
View file

@ -6887,6 +6887,8 @@ SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
{ {
struct task_struct *p; struct task_struct *p;
unsigned int time_slice; unsigned int time_slice;
unsigned long flags;
struct rq *rq;
int retval; int retval;
struct timespec t; struct timespec t;
@ -6903,7 +6905,9 @@ SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
if (retval) if (retval)
goto out_unlock; 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); read_unlock(&tasklist_lock);
jiffies_to_timespec(time_slice, &t); jiffies_to_timespec(time_slice, &t);

6
kernel/sched_fair.c
View file

@ -2014,21 +2014,17 @@ static void moved_group_fair(struct task_struct *p)
} }
#endif #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; struct sched_entity *se = &task->se;
unsigned long flags;
struct rq *rq;
unsigned int rr_interval = 0; unsigned int rr_interval = 0;
/* /*
* Time slice is 0 for SCHED_OTHER tasks that are on an otherwise * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
* idle runqueue: * idle runqueue:
*/ */
rq = task_rq_lock(task, &flags);
if (rq->cfs.load.weight) if (rq->cfs.load.weight)
rr_interval = NS_TO_JIFFIES(sched_slice(&rq->cfs, se)); rr_interval = NS_TO_JIFFIES(sched_slice(&rq->cfs, se));
task_rq_unlock(rq, &flags);
return rr_interval; return rr_interval;
} }

2
kernel/sched_idletask.c
View file

@ -97,7 +97,7 @@ static void prio_changed_idle(struct rq *rq, struct task_struct *p,
check_preempt_curr(rq, p, 0); 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; return 0;
} }

2
kernel/sched_rt.c
View file

@ -1721,7 +1721,7 @@ static void set_curr_task_rt(struct rq *rq)
dequeue_pushable_task(rq, p); 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 * Time slice is 0 for SCHED_FIFO tasks