[PATCH] workqueue: Introduce show_freeze_workqueues_busy

[Jungseung Lee]

Currently show_all_workqueue() is called if freeze fails at the time of
freeze the workqueues, which shows the status of all workqueues and
of all worker pools. In this cases we may only need to dump state of
only workqueues that are freezable and busy.

This patch defines show_freeze_workqueues_busy, which uses
show_one_workqueue, a granular function that shows the state of
individual workqueues, so that dump only the state of freezable
workqueues at that time.

Signed-off-by: Jungseung Lee <js07.lee@xxxxxxxxxxx>
---
 include/linux/workqueue.h |  1 +
 kernel/power/process.c    |  2 +-
 kernel/workqueue.c        | 25 ++++++++++++++++++++++++-
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 0a10f8e..3d68631 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -472,6 +472,7 @@ extern unsigned int work_busy(struct work_struct *work);
 extern __printf(1, 2) void set_worker_desc(const char *fmt, ...);
 extern void print_worker_info(const char *log_lvl, struct task_struct *task);
 extern void show_all_workqueues(void);
+extern void show_freeze_workqueues_busy(void);
 extern void show_one_workqueue(struct workqueue_struct *wq);
 extern void wq_worker_comm(char *buf, size_t size, struct task_struct *task);
 
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 6c1c7e5..590550f 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -93,7 +93,7 @@ static int try_to_freeze_tasks(bool user_only)
 		       todo - wq_busy, wq_busy);
 
 		if (wq_busy)
-			show_all_workqueues();
+			show_freeze_workqueues_busy();
 
 		if (!wakeup || pm_debug_messages_on) {
 			read_lock(&tasklist_lock);
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index de42827..087eedb 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5043,7 +5043,7 @@ static void show_one_worker_pool(struct worker_pool *pool)
 /**
  * show_all_workqueues - dump workqueue state
  *
- * Called from a sysrq handler or try_to_freeze_tasks() and prints out
+ * Called from a sysrq handler and prints out
  * all busy workqueues and pools.
  */
 void show_all_workqueues(void)
@@ -5065,6 +5065,29 @@ void show_all_workqueues(void)
 	rcu_read_unlock();
 }
 
+/**
+ * show_freeze_workqueues_busy - dump freezable workqueue state
+ *
+ * Called from try_to_freeze_tasks() and prints out
+ * all freezable workqueues still busy.
+ */
+void show_freeze_workqueues_busy(void)
+{
+	struct workqueue_struct *wq;
+
+	rcu_read_lock();
+
+	pr_info("Showing freezable workqueues still busy:\n");
+
+	list_for_each_entry_rcu(wq, &workqueues, list) {
+		if (!(wq->flags & WQ_FREEZABLE))
+			continue;
+		show_one_workqueue(wq);
+	}
+
+	rcu_read_unlock();
+}
+
 /* used to show worker information through /proc/PID/{comm,stat,status} */
 void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
 {
-- 
2.7.4