[PATCH 1/5] workqueue: implement workqueue_on_rescuer()

[Tejun Heo <tj@kernel.org>]

workqueue_on_rescuer() tests whether the caller is running on the
rescuer of the specified workqueue.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 include/linux/workqueue.h |    1 +
 kernel/workqueue.c        |   15 +++++++++++++++
 2 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index f11100f..c988063 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -339,6 +339,7 @@ extern int cancel_work_sync(struct work_struct *work);
 extern void workqueue_set_max_active(struct workqueue_struct *wq,
 				     int max_active);
 extern bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq);
+extern bool workqueue_on_rescuer(struct workqueue_struct *wq);
 extern unsigned int work_cpu(struct work_struct *work);
 extern unsigned int work_busy(struct work_struct *work);
 
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 727f24e..a91e1ca 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2941,6 +2941,21 @@ bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq)
 EXPORT_SYMBOL_GPL(workqueue_congested);
 
 /**
+ * workqueue_on_rescuer - test whether executing on the rescuer
+ * @wq: target workqueue
+ *
+ * Test whether the caller is currently executing on @wq's rescuer.
+ *
+ * RETURNS:
+ * %true if executing on @wq's rescuer, %false otherwise.
+ */
+bool workqueue_on_rescuer(struct workqueue_struct *wq)
+{
+	return wq->rescuer && current == wq->rescuer->task;
+}
+EXPORT_SYMBOL_GPL(workqueue_on_rescuer);
+
+/**
  * work_cpu - return the last known associated cpu for @work
  * @work: the work of interest
  *
-- 
1.7.1