linux-kernel - [PATCH v4 06/22] kthread: Add destroy_kthread

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Date:	Mon, 25 Jan 2016 16:44:55 +0100
From:	Petr Mladek <pmladek@...e.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josh@...htriplett.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>, Borislav Petkov <bp@...e.de>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	Vlastimil Babka <vbabka@...e.cz>, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org, Petr Mladek <pmladek@...e.com>
Subject: [PATCH v4 06/22] kthread: Add destroy_kthread_worker()

The current kthread worker users call flush() and stop() explicitly.
This function drains the worker, stops it, and frees the kthread_worker
struct in one call.

It is supposed to be used together with create_kthread_worker*() that
allocates struct kthread_worker.

Also note that drain() correctly handles self-queuing works in compare
with flush().

Signed-off-by: Petr Mladek <pmladek@...e.com>
---
 include/linux/kthread.h |  2 ++
 kernel/kthread.c        | 21 +++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 943900c7ce35..c4a95a3ba500 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -136,4 +136,6 @@ bool queue_kthread_work(struct kthread_worker *worker,
 void flush_kthread_work(struct kthread_work *work);
 void flush_kthread_worker(struct kthread_worker *worker);
 
+void destroy_kthread_worker(struct kthread_worker *worker);
+
 #endif /* _LINUX_KTHREAD_H */
diff --git a/kernel/kthread.c b/kernel/kthread.c
index a18ad3b58f61..1d41e0faef2d 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -838,3 +838,24 @@ void drain_kthread_worker(struct kthread_worker *worker)
 	spin_unlock_irq(&worker->lock);
 }
 EXPORT_SYMBOL(drain_kthread_worker);
+
+/**
+ * destroy_kthread_worker - destroy a kthread worker
+ * @worker: worker to be destroyed
+ *
+ * Drain and destroy @worker.  It has the same conditions
+ * for use as drain_kthread_worker(), see above.
+ */
+void destroy_kthread_worker(struct kthread_worker *worker)
+{
+	struct task_struct *task;
+
+	task = worker->task;
+	if (WARN_ON(!task))
+		return;
+
+	drain_kthread_worker(worker);
+	kthread_stop(task);
+	kfree(worker);
+}
+EXPORT_SYMBOL(destroy_kthread_worker);
-- 
1.8.5.6