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

commit dba091b9e3522b9d32fc9975e48d3b69633b45f0 upstream

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>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/include/linux/sched.h b/include/linux/sched.h
index cc24bebf80193674bd7f4a6776f9e89b685d5484..6d42a524497cfa44ca3f970679e4e9cad2d77894 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1114,7 +1114,8 @@ 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);

diff --git a/kernel/sched.c b/kernel/sched.c
index eaf30be616e554b1a435092943e1eb63cb3833b5..8554f124a3e9f754b8df53089e7407a199a0a8bf 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6946,6 +6946,8 @@ 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;
 
@@ -6962,7 +6964,9 @@ 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);

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index d80812d39d6238378ccac64538056d762128f084..803a9d2afcfa6508924e480f62b0c72e06edcd78 100644 (file)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -2003,21 +2003,17 @@ 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;
 }

diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c
index b133a28fcde32cbf20421f077686c14319871f74..33d5384a73a86b09a0493600ce4e4b06cf1b9ac5 100644 (file)
--- a/kernel/sched_idletask.c
+++ b/kernel/sched_idletask.c
@@ -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;
 }

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index a4d790cddb1983196ba9881936d8abf7a8870dbe..a9320d46046b899bef08623608731ab06eda0e26 100644 (file)
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -1734,7 +1734,7 @@ 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