[PATCH 08/10] workqueue: assign overflowed flushers's flush color when queued

[Lai Jiangshan]

wq->work_color is unchanged between overflowed flusher queued on
 ->flusher_overflow and requeued on ->flusher_queue.

So we can assign overflowed flushers's flush color when they are queued
on ->flusher_overflow.

This patch makes the flusher's flush color more clear:
        flusher's flush color is the work color of the WQ
        when flush_workqueue() starts.

Remove an unneeded loop.

This patch doesn't make any functional difference.

Signed-off-by: Lai Jiangshan <la...@cn.fujitsu.com>
---
 kernel/workqueue.c |   19 +++++++++----------
 1 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index be407e1..f687893 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2613,11 +2613,11 @@ void flush_workqueue(struct workqueue_struct *wq)
         */
        flush_color = wq->work_color;
        next_color = work_next_color(wq->work_color);
+       this_flusher.flush_color = flush_color;
 
        if (next_color != wq->flush_color) {
                /* Color space is not full */
                BUG_ON(!list_empty(&wq->flusher_overflow));
-               this_flusher.flush_color = flush_color;
 
                if (!wq->first_flusher) {
                        /* no flush in progress, become the first flusher */
@@ -2643,8 +2643,8 @@ void flush_workqueue(struct workqueue_struct *wq)
        } else {
                /*
                 * Oops, color space is full, wait on overflow queue.
-                * The next flush completion will assign us
-                * flush_color and transfer to flusher_queue.
+                * The next flush completion will start flush for us
+                * with freed flush color and transfer us to flusher_queue.
                 */
                list_add_tail(&this_flusher.list, &wq->flusher_overflow);
        }
@@ -2684,15 +2684,14 @@ void flush_workqueue(struct workqueue_struct *wq)
 
        /* one color has been freed, handle overflow queue */
        if (!list_empty(&wq->flusher_overflow)) {
+               BUG_ON(list_first_entry(&wq->flusher_overflow,
+                                       struct wq_flusher,
+                                       list)->flush_color
+                      != wq->work_color);
                /*
-                * Assign the same color to all overflowed
-                * flushers, advance work_color and append to
-                * flusher_queue.  This is the start-to-wait
-                * phase for these overflowed flushers.
+                * start flush with the freed color and append
+                * overflowed flushers to the flusher_queue.
                 */
-               list_for_each_entry(tmp, &wq->flusher_overflow, list)
-                       tmp->flush_color = wq->work_color;
-
                list_splice_tail_init(&wq->flusher_overflow,
                                      &wq->flusher_queue);
                workqueue_start_flush(wq);
-- 
1.7.4.4

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