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authorPeter Zijlstra <peterz@infradead.org>2015-05-15 17:43:34 +0200
committerIngo Molnar <mingo@kernel.org>2015-08-12 12:06:09 +0200
commit25834c73f93af7f0712c98ca4593691592e6b360 (patch)
tree5da4f7c4da2a85ba6458a4de234da5e3d0a0c27a /kernel/kthread.c
parent7855a35ac07a350e2cd26f09568a6d8e372be358 (diff)
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sched: Fix a race between __kthread_bind() and sched_setaffinity()
Because sched_setscheduler() checks p->flags & PF_NO_SETAFFINITY without locks, a caller might observe an old value and race with the set_cpus_allowed_ptr() call from __kthread_bind() and effectively undo it: __kthread_bind() do_set_cpus_allowed() <SYSCALL> sched_setaffinity() if (p->flags & PF_NO_SETAFFINITIY) set_cpus_allowed_ptr() p->flags |= PF_NO_SETAFFINITY Fix the bug by putting everything under the regular scheduler locks. This also closes a hole in the serialization of task_struct::{nr_,}cpus_allowed. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Tejun Heo <tj@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dedekind1@gmail.com Cc: juri.lelli@arm.com Cc: mgorman@suse.de Cc: riel@redhat.com Cc: rostedt@goodmis.org Link: http://lkml.kernel.org/r/20150515154833.545640346@infradead.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/kthread.c')
-rw-r--r--kernel/kthread.c20
1 files changed, 17 insertions, 3 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 10e489c448fe..7c40a189becc 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -325,16 +325,30 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
}
EXPORT_SYMBOL(kthread_create_on_node);
-static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
+static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
{
- /* Must have done schedule() in kthread() before we set_task_cpu */
+ unsigned long flags;
+
if (!wait_task_inactive(p, state)) {
WARN_ON(1);
return;
}
+
/* It's safe because the task is inactive. */
- do_set_cpus_allowed(p, cpumask_of(cpu));
+ raw_spin_lock_irqsave(&p->pi_lock, flags);
+ do_set_cpus_allowed(p, mask);
p->flags |= PF_NO_SETAFFINITY;
+ raw_spin_unlock_irqrestore(&p->pi_lock, flags);
+}
+
+static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
+{
+ __kthread_bind_mask(p, cpumask_of(cpu), state);
+}
+
+void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
+{
+ __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
}
/**