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From: Tejun Heo on 28 Jun 2010 17:10
Now that all the workers are tracked by gcwq, we can find which worker
is executing a work from gcwq. Implement find_worker_executing_work()
and make worker track its current_cwq so that we can find things the
other way around. This will be used to implement non-reentrant wqs.

Signed-off-by: Tejun Heo <tj(a)kernel.org>
---
kernel/workqueue.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 56 insertions(+), 0 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 2ce895e..7111683 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -82,6 +82,7 @@ struct worker {
};

struct work_struct *current_work; /* L: work being processed */
+ struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */
struct list_head scheduled; /* L: scheduled works */
struct task_struct *task; /* I: worker task */
struct global_cwq *gcwq; /* I: the associated gcwq */
@@ -373,6 +374,59 @@ static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
}

/**
+ * __find_worker_executing_work - find worker which is executing a work
+ * @gcwq: gcwq of interest
+ * @bwh: hash head as returned by busy_worker_head()
+ * @work: work to find worker for
+ *
+ * Find a worker which is executing @work on @gcwq. @bwh should be
+ * the hash head obtained by calling busy_worker_head() with the same
+ * work.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock).
+ *
+ * RETURNS:
+ * Pointer to worker which is executing @work if found, NULL
+ * otherwise.
+ */
+static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
+ struct hlist_head *bwh,
+ struct work_struct *work)
+{
+ struct worker *worker;
+ struct hlist_node *tmp;
+
+ hlist_for_each_entry(worker, tmp, bwh, hentry)
+ if (worker->current_work == work)
+ return worker;
+ return NULL;
+}
+
+/**
+ * find_worker_executing_work - find worker which is executing a work
+ * @gcwq: gcwq of interest
+ * @work: work to find worker for
+ *
+ * Find a worker which is executing @work on @gcwq. This function is
+ * identical to __find_worker_executing_work() except that this
+ * function calculates @bwh itself.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock).
+ *
+ * RETURNS:
+ * Pointer to worker which is executing @work if found, NULL
+ * otherwise.
+ */
+static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
+ struct work_struct *work)
+{
+ return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
+ work);
+}
+
+/**
* insert_work - insert a work into cwq
* @cwq: cwq @work belongs to
* @work: work to insert
@@ -914,6 +968,7 @@ static void process_one_work(struct worker *worker, struct work_struct *work)
debug_work_deactivate(work);
hlist_add_head(&worker->hentry, bwh);
worker->current_work = work;
+ worker->current_cwq = cwq;
work_color = get_work_color(work);
list_del_init(&work->entry);

@@ -942,6 +997,7 @@ static void process_one_work(struct worker *worker, struct work_struct *work)
/* we're done with it, release */
hlist_del_init(&worker->hentry);
worker->current_work = NULL;
+ worker->current_cwq = NULL;
cwq_dec_nr_in_flight(cwq, work_color);
}

--
1.6.4.2

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Prev: [PATCH 16/35] workqueue: implement per-cwq active work limit
Next: [PATCH 17/35] workqueue: reimplement workqueue freeze using max_active