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    Subject[PATCH 10/10] workqueue: remove wq->flush_color
    Date
    Use wq->first_flusher->flush_color instead.

    If current task is the first_flusher, we use @flush_color
    or work_next_color(flush_color) directly.

    This patch doesn't make any functional difference.

    Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
    ---
    kernel/workqueue.c | 52 ++++++++++++++++++++--------------------------------
    1 files changed, 20 insertions(+), 32 deletions(-)

    diff --git a/kernel/workqueue.c b/kernel/workqueue.c
    index d78fe08..e703659 100644
    --- a/kernel/workqueue.c
    +++ b/kernel/workqueue.c
    @@ -248,7 +248,6 @@ struct workqueue_struct {

    struct mutex flush_mutex; /* protects wq flushing */
    int work_color; /* F: current work color */
    - int flush_color; /* F: current flush color */
    atomic_t nr_cwqs_to_flush[WORK_NR_COLORS];
    struct wq_flusher *first_flusher; /* F: first flusher */
    struct list_head flusher_queue; /* F: flush waiters */
    @@ -2555,7 +2554,7 @@ static bool workqueue_start_flush(struct workqueue_struct *wq)
    bool wait = false;
    unsigned int cpu;

    - BUG_ON(next_color == wq->flush_color);
    + BUG_ON(next_color == wq->first_flusher->flush_color);
    wq->work_color = next_color;

    BUG_ON(atomic_read(&wq->nr_cwqs_to_flush[flush_color]));
    @@ -2614,29 +2613,23 @@ void flush_workqueue(struct workqueue_struct *wq)
    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 */
    - if (!wq->first_flusher) {
    - /* no flush in progress, become the first flusher */
    - BUG_ON(wq->flush_color != flush_color);
    -
    - wq->first_flusher = &this_flusher;
    -
    - if (!workqueue_start_flush(wq)) {
    - /* nothing to flush, done */
    - wq_dec_flusher_ref(wq, flush_color);
    - wq->flush_color = next_color;
    - wq->first_flusher = NULL;
    - goto out_unlock;
    - }
    + if (!wq->first_flusher) {
    + /* no flush in progress, become the first flusher */
    + wq->first_flusher = &this_flusher;

    + if (!workqueue_start_flush(wq)) {
    + /* nothing to flush, done */
    wq_dec_flusher_ref(wq, flush_color);
    - } else {
    - /* wait in queue */
    - BUG_ON(wq->flush_color == this_flusher.flush_color);
    - list_add_tail(&this_flusher.list, &wq->flusher_queue);
    - workqueue_start_flush(wq);
    + wq->first_flusher = NULL;
    + goto out_unlock;
    }
    +
    + wq_dec_flusher_ref(wq, flush_color);
    + } else if (next_color != wq->first_flusher->flush_color) {
    + /* Color space is not full, wait in queue */
    + BUG_ON(wq->first_flusher->flush_color == flush_color);
    + list_add_tail(&this_flusher.list, &wq->flusher_queue);
    + workqueue_start_flush(wq);
    } else {
    /*
    * Oops, color space is full, queue it without starting flush.
    @@ -2663,21 +2656,17 @@ void flush_workqueue(struct workqueue_struct *wq)

    BUG_ON(wq->first_flusher != &this_flusher);
    BUG_ON(!list_empty(&this_flusher.list));
    - BUG_ON(wq->flush_color != this_flusher.flush_color);

    /* complete all the flushers sharing the current flush color */
    list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
    - if (next->flush_color != wq->flush_color)
    + if (next->flush_color != flush_color)
    break;
    list_del_init(&next->list);
    complete(&next->done);
    }

    - /* this flush_color is finished, advance by one */
    - wq->flush_color = work_next_color(wq->flush_color);
    -
    if (list_empty(&wq->flusher_queue)) {
    - BUG_ON(wq->flush_color != wq->work_color);
    + BUG_ON(work_next_color(flush_color) != wq->work_color);
    wq->first_flusher = NULL;
    goto out_unlock;
    }
    @@ -2686,9 +2675,6 @@ void flush_workqueue(struct workqueue_struct *wq)
    * Need to flush more colors. Make the next flusher
    * the new first flusher and arm it.
    */
    - BUG_ON(wq->flush_color == wq->work_color);
    - BUG_ON(wq->flush_color != next->flush_color);
    -
    last = list_entry(wq->flusher_queue.prev, struct wq_flusher, list);
    list_del_init(&next->list);
    wq->first_flusher = next;
    @@ -2698,9 +2684,11 @@ void flush_workqueue(struct workqueue_struct *wq)
    workqueue_start_flush(wq);

    BUG_ON(work_next_color(last->flush_color) != wq->work_color);
    + BUG_ON(work_next_color(flush_color) != next->flush_color);
    + BUG_ON(next->flush_color == wq->work_color);

    /* arm new first flusher */
    - wq_dec_flusher_ref(wq, wq->flush_color);
    + wq_dec_flusher_ref(wq, next->flush_color);

    out_unlock:
    mutex_unlock(&wq->flush_mutex);
    --
    1.7.4.4


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