workqueue: implement several utility APIs

Implement the following utility APIs.

 workqueue_set_max_active()	: adjust max_active of a wq
 workqueue_congested()		: test whether a wq is contested
 work_cpu()			: determine the last / current cpu of a work
 work_busy()			: query whether a work is busy

* Anton Blanchard fixed missing ret initialization in work_busy().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Anton Blanchard <anton@samba.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 48b7422f25ae..0a7f79729380 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -61,6 +61,10 @@ enum {
         WORK_STRUCT_FLAG_MASK   = (1UL << WORK_STRUCT_FLAG_BITS) - 1,
         WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK,
         WORK_STRUCT_NO_CPU      = NR_CPUS << WORK_STRUCT_FLAG_BITS,
+
+        /* bit mask for work_busy() return values */
+        WORK_BUSY_PENDING       = 1 << 0,
+        WORK_BUSY_RUNNING       = 1 << 1,
 };
 
 struct work_struct {
@@ -307,9 +311,14 @@ extern void init_workqueues(void);
 int execute_in_process_context(work_func_t fn, struct execute_work *);
 
 extern int flush_work(struct work_struct *work);
-
 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 unsigned int work_cpu(struct work_struct *work);
+extern unsigned int work_busy(struct work_struct *work);
+
 /*
  * Kill off a pending schedule_delayed_work().  Note that the work callback
  * function may still be running on return from cancel_delayed_work(), unless