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Subject[PATCH RT 8/9][RFC] [PATCH 8/9] workqueue: Revert workqueue: Fix PF_THREAD_BOUND abuse
Revert commit

Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Mon Oct 3 12:43:25 2011 +0200
workqueue: Fix PF_THREAD_BOUND abuse

As TREAD_BOUND no longer affects cpu down, and this code introduced
a lot of races with taking down a CPU.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/workqueue.c | 29 +++++++++--------------------
1 files changed, 9 insertions(+), 20 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index e7f3e79..3b53135 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1286,14 +1286,8 @@ __acquires(&gcwq->lock)
return false;
if (task_cpu(task) == gcwq->cpu &&
cpumask_equal(&current->cpus_allowed,
- get_cpu_mask(gcwq->cpu))) {
- /*
- * Since we're binding to a particular cpu and need to
- * stay there for correctness, mark us PF_THREAD_BOUND.
- */
- task->flags |= PF_THREAD_BOUND;
+ get_cpu_mask(gcwq->cpu)))
return true;
- }
spin_unlock_irq(&gcwq->lock);

/*
@@ -1307,18 +1301,6 @@ __acquires(&gcwq->lock)
}
}

-static void worker_unbind_and_unlock(struct worker *worker)
-{
- struct global_cwq *gcwq = worker->gcwq;
- struct task_struct *task = worker->task;
-
- /*
- * Its no longer required we're PF_THREAD_BOUND, the work is done.
- */
- task->flags &= ~PF_THREAD_BOUND;
- spin_unlock_irq(&gcwq->lock);
-}
-
static struct worker *alloc_worker(void)
{
struct worker *worker;
@@ -1381,9 +1363,15 @@ static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
if (IS_ERR(worker->task))
goto fail;

+ /*
+ * A rogue worker will become a regular one if CPU comes
+ * online later on. Make sure every worker has
+ * PF_THREAD_BOUND set.
+ */
if (bind && !on_unbound_cpu)
kthread_bind(worker->task, gcwq->cpu);
else {
+ worker->task->flags |= PF_THREAD_BOUND;
if (on_unbound_cpu)
worker->flags |= WORKER_UNBOUND;
}
@@ -2060,7 +2048,7 @@ repeat:
if (keep_working(gcwq))
wake_up_worker(gcwq);

- worker_unbind_and_unlock(rescuer);
+ spin_unlock_irq(&gcwq->lock);
}

schedule();
@@ -3009,6 +2997,7 @@ struct workqueue_struct *__alloc_workqueue_key(const char *name,
if (IS_ERR(rescuer->task))
goto err;

+ rescuer->task->flags |= PF_THREAD_BOUND;
wake_up_process(rescuer->task);
}

--
1.7.3.4



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