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sched: Use rcu in sched_get/set_affinity()
tasklist_lock is held read locked to protect the find_task_by_vpid() call and to prevent the task going away. sched_setaffinity acquires a task struct ref and drops tasklist lock right away. The access to the cpus_allowed mask is protected by rq->lock. rcu_read_lock() provides the same protection here. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> LKML-Reference: <20091209100706.789059966@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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parent
5fe85be081
commit
23f5d14251
1 changed files with 6 additions and 10 deletions
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@ -6516,22 +6516,18 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
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int retval;
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get_online_cpus();
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read_lock(&tasklist_lock);
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rcu_read_lock();
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p = find_process_by_pid(pid);
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if (!p) {
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read_unlock(&tasklist_lock);
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rcu_read_unlock();
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put_online_cpus();
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return -ESRCH;
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}
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/*
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* It is not safe to call set_cpus_allowed with the
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* tasklist_lock held. We will bump the task_struct's
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* usage count and then drop tasklist_lock.
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*/
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/* Prevent p going away */
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get_task_struct(p);
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read_unlock(&tasklist_lock);
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rcu_read_unlock();
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if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
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retval = -ENOMEM;
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@ -6617,7 +6613,7 @@ long sched_getaffinity(pid_t pid, struct cpumask *mask)
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int retval;
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get_online_cpus();
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read_lock(&tasklist_lock);
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rcu_read_lock();
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retval = -ESRCH;
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p = find_process_by_pid(pid);
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@ -6633,7 +6629,7 @@ long sched_getaffinity(pid_t pid, struct cpumask *mask)
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task_rq_unlock(rq, &flags);
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out_unlock:
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read_unlock(&tasklist_lock);
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rcu_read_unlock();
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put_online_cpus();
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return retval;
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