Messages in this thread Patch in this message | | | Date | Wed, 9 Dec 2009 09:32:03 +0100 (CET) | From | Thomas Gleixner <> | Subject | [patch V2 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> --- include/linux/sched.h | 3 ++- kernel/sched.c | 6 +++++- kernel/sched_fair.c | 6 +----- kernel/sched_idletask.c | 2 +- kernel/sched_rt.c | 2 +- 5 files changed, 10 insertions(+), 9 deletions(-)
Index: linux-2.6-tip/include/linux/sched.h =================================================================== --- linux-2.6-tip.orig/include/linux/sched.h +++ linux-2.6-tip/include/linux/sched.h @@ -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); 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; - 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); Index: linux-2.6-tip/kernel/sched_fair.c =================================================================== --- linux-2.6-tip.orig/kernel/sched_fair.c +++ linux-2.6-tip/kernel/sched_fair.c @@ -2014,21 +2014,17 @@ static void moved_group_fair(struct task } #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; } Index: linux-2.6-tip/kernel/sched_idletask.c =================================================================== --- linux-2.6-tip.orig/kernel/sched_idletask.c +++ linux-2.6-tip/kernel/sched_idletask.c @@ -97,7 +97,7 @@ static void prio_changed_idle(struct rq 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; } Index: linux-2.6-tip/kernel/sched_rt.c =================================================================== --- linux-2.6-tip.orig/kernel/sched_rt.c +++ linux-2.6-tip/kernel/sched_rt.c @@ -1721,7 +1721,7 @@ static void set_curr_task_rt(struct 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
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