From f2e89e181d71e35e621d40ec185689347efe5dd9 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Fri, 3 Aug 2012 10:30:46 -0700
Subject: [PATCH] --- yaml --- r: 327157 b: refs/heads/master c:
 b5490077274482efde57a50b060b99bc839acd45 h: refs/heads/master i:   327155:
 d0602743780c046562d8ca19280c52f4e59f0906 v: v3

---
 [refs]                          |  2 +-
 trunk/include/linux/workqueue.h |  8 +++++++-
 trunk/kernel/workqueue.c        | 14 +++++++++-----
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/[refs] b/[refs]
index 9441df14fa15..a27e6ea80063 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: bf4ede014ea886b71ef71368738da35b316cb7c0
+refs/heads/master: b5490077274482efde57a50b060b99bc839acd45
diff --git a/trunk/include/linux/workqueue.h b/trunk/include/linux/workqueue.h
index ab95fef38d56..f562674db404 100644
--- a/trunk/include/linux/workqueue.h
+++ b/trunk/include/linux/workqueue.h
@@ -68,9 +68,15 @@ enum {
 	WORK_STRUCT_FLAG_BITS	= WORK_STRUCT_COLOR_SHIFT +
 				  WORK_STRUCT_COLOR_BITS,
 
+	/* data contains off-queue information when !WORK_STRUCT_CWQ */
+	WORK_OFFQ_FLAG_BASE	= WORK_STRUCT_FLAG_BITS,
+	WORK_OFFQ_FLAG_BITS	= 0,
+	WORK_OFFQ_CPU_SHIFT	= WORK_OFFQ_FLAG_BASE + WORK_OFFQ_FLAG_BITS,
+
+	/* convenience constants */
 	WORK_STRUCT_FLAG_MASK	= (1UL << WORK_STRUCT_FLAG_BITS) - 1,
 	WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK,
-	WORK_STRUCT_NO_CPU	= WORK_CPU_NONE << WORK_STRUCT_FLAG_BITS,
+	WORK_STRUCT_NO_CPU	= (unsigned long)WORK_CPU_NONE << WORK_OFFQ_CPU_SHIFT,
 
 	/* bit mask for work_busy() return values */
 	WORK_BUSY_PENDING	= 1 << 0,
diff --git a/trunk/kernel/workqueue.c b/trunk/kernel/workqueue.c
index 0f50f4078e36..eeae77079483 100644
--- a/trunk/kernel/workqueue.c
+++ b/trunk/kernel/workqueue.c
@@ -533,9 +533,9 @@ static int work_next_color(int color)
 }
 
 /*
- * A work's data points to the cwq with WORK_STRUCT_CWQ set while the
- * work is on queue.  Once execution starts, WORK_STRUCT_CWQ is
- * cleared and the work data contains the cpu number it was last on.
+ * While queued, %WORK_STRUCT_CWQ is set and non flag bits of a work's data
+ * contain the pointer to the queued cwq.  Once execution starts, the flag
+ * is cleared and the high bits contain OFFQ flags and CPU number.
  *
  * set_work_cwq(), set_work_cpu_and_clear_pending() and clear_work_data()
  * can be used to set the cwq, cpu or clear work->data.  These functions
@@ -565,7 +565,7 @@ static void set_work_cwq(struct work_struct *work,
 static void set_work_cpu_and_clear_pending(struct work_struct *work,
 					   unsigned int cpu)
 {
-	set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, 0);
+	set_work_data(work, (unsigned long)cpu << WORK_OFFQ_CPU_SHIFT, 0);
 }
 
 static void clear_work_data(struct work_struct *work)
@@ -592,7 +592,7 @@ static struct global_cwq *get_work_gcwq(struct work_struct *work)
 		return ((struct cpu_workqueue_struct *)
 			(data & WORK_STRUCT_WQ_DATA_MASK))->pool->gcwq;
 
-	cpu = data >> WORK_STRUCT_FLAG_BITS;
+	cpu = data >> WORK_OFFQ_CPU_SHIFT;
 	if (cpu == WORK_CPU_NONE)
 		return NULL;
 
@@ -3724,6 +3724,10 @@ static int __init init_workqueues(void)
 	unsigned int cpu;
 	int i;
 
+	/* make sure we have enough bits for OFFQ CPU number */
+	BUILD_BUG_ON((1LU << (BITS_PER_LONG - WORK_OFFQ_CPU_SHIFT)) <
+		     WORK_CPU_LAST);
+
 	cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
 	cpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);