[PATCH RT 10/12] workqueue: Revert workqueue: Fix PF_THREAD_BOUND abuse

[Steven Rostedt]

From: Steven Rostedt <srost...@redhat.com>

Revert commit

    Author: Peter Zijlstra <a.p.zijls...@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 <rost...@goodmis.org>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
 kernel/workqueue.c |   29 +++++++++--------------------
 1 file changed, 9 insertions(+), 20 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index a08a963..53268e3 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1287,14 +1287,8 @@ __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);
 
                /*
@@ -1308,18 +1302,6 @@ __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;
@@ -1382,9 +1364,15 @@ 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;
        }
@@ -2061,7 +2049,7 @@ repeat:
                if (keep_working(gcwq))
                        wake_up_worker(gcwq);
 
-               worker_unbind_and_unlock(rescuer);
+               spin_unlock_irq(&gcwq->lock);
        }
 
        schedule();
@@ -2957,6 +2945,7 @@ 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);
        }
 
-- 
1.7.10.4


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