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authorTejun Heo <tj@kernel.org>2010-06-29 12:07:11 +0400
committerTejun Heo <tj@kernel.org>2010-06-29 12:07:11 +0400
commit73f53c4aa732eced5fcb1844d3d452c30905f20f (patch)
tree6185ebab8337d33de9ca9c3d19fc5217bc4ee6bc /include/linux/workqueue.h
parent0f900049cbe2767d47c2a62b54f0e822e1d66840 (diff)
downloadlinux-73f53c4aa732eced5fcb1844d3d452c30905f20f.tar.xz
workqueue: reimplement workqueue flushing using color coded works
Reimplement workqueue flushing using color coded works. wq has the current work color which is painted on the works being issued via cwqs. Flushing a workqueue is achieved by advancing the current work colors of cwqs and waiting for all the works which have any of the previous colors to drain. Currently there are 16 possible colors, one is reserved for no color and 15 colors are useable allowing 14 concurrent flushes. When color space gets full, flush attempts are batched up and processed together when color frees up, so even with many concurrent flushers, the new implementation won't build up huge queue of flushers which has to be processed one after another. Only works which are queued via __queue_work() are colored. Works which are directly put on queue using insert_work() use NO_COLOR and don't participate in workqueue flushing. Currently only works used for work-specific flush fall in this category. This new implementation leaves only cleanup_workqueue_thread() as the user of flush_cpu_workqueue(). Just make its users use flush_workqueue() and kthread_stop() directly and kill cleanup_workqueue_thread(). As workqueue flushing doesn't use barrier request anymore, the comment describing the complex synchronization around it in cleanup_workqueue_thread() is removed together with the function. This new implementation is to allow having and sharing multiple workers per cpu. Please note that one more bit is reserved for a future work flag by this patch. This is to avoid shifting bits and updating comments later. Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'include/linux/workqueue.h')
-rw-r--r--include/linux/workqueue.h21
1 files changed, 19 insertions, 2 deletions
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index b90958a037dc..8762f62103d8 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -26,11 +26,13 @@ enum {
WORK_STRUCT_PENDING_BIT = 0, /* work item is pending execution */
#ifdef CONFIG_DEBUG_OBJECTS_WORK
WORK_STRUCT_STATIC_BIT = 1, /* static initializer (debugobjects) */
- WORK_STRUCT_FLAG_BITS = 2,
+ WORK_STRUCT_COLOR_SHIFT = 3, /* color for workqueue flushing */
#else
- WORK_STRUCT_FLAG_BITS = 1,
+ WORK_STRUCT_COLOR_SHIFT = 2, /* color for workqueue flushing */
#endif
+ WORK_STRUCT_COLOR_BITS = 4,
+
WORK_STRUCT_PENDING = 1 << WORK_STRUCT_PENDING_BIT,
#ifdef CONFIG_DEBUG_OBJECTS_WORK
WORK_STRUCT_STATIC = 1 << WORK_STRUCT_STATIC_BIT,
@@ -38,6 +40,21 @@ enum {
WORK_STRUCT_STATIC = 0,
#endif
+ /*
+ * The last color is no color used for works which don't
+ * participate in workqueue flushing.
+ */
+ WORK_NR_COLORS = (1 << WORK_STRUCT_COLOR_BITS) - 1,
+ WORK_NO_COLOR = WORK_NR_COLORS,
+
+ /*
+ * Reserve 6 bits off of cwq pointer w/ debugobjects turned
+ * off. This makes cwqs aligned to 64 bytes which isn't too
+ * excessive while allowing 15 workqueue flush colors.
+ */
+ WORK_STRUCT_FLAG_BITS = WORK_STRUCT_COLOR_SHIFT +
+ WORK_STRUCT_COLOR_BITS,
+
WORK_STRUCT_FLAG_MASK = (1UL << WORK_STRUCT_FLAG_BITS) - 1,
WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK,
};