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From: Petr Mladek <pmladek@suse.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Oleg Nesterov <oleg@redhat.com>, Tejun Heo <tj@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Josh Triplett <josh@joshtriplett.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Jiri Kosina <jkosina@suse.cz>, Borislav Petkov <bp@suse.de>,
	Michal Hocko <mhocko@suse.cz>,
	linux-mm@kvack.org, Vlastimil Babka <vbabka@suse.cz>,
	linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
	Petr Mladek <pmladek@suse.com>
Subject: [PATCH v6 09/20] kthread: Allow to modify delayed kthread work
Date: Thu, 14 Apr 2016 17:14:28 +0200	[thread overview]
Message-ID: <1460646879-617-10-git-send-email-pmladek@suse.com> (raw)
In-Reply-To: <1460646879-617-1-git-send-email-pmladek@suse.com>

There are situations when we need to modify the delay of a delayed kthread
work. For example, when the work depends on an event and the initial delay
means a timeout. Then we want to queue the work immediately when the event
happens.

This patch implements mod_delayed_kthread_work() as inspired workqueues.
It cancels the timer, removes the work from any worker list and queues it
again with the given timeout.

A very special case is when the work is being canceled at the same time.
It might happen because of the regular cancel_delayed_kthread_work_sync()
or by another mod_delayed_kthread_work(). In this case, we do nothing and
let the other operation win. This should not normally happen as the caller
is supposed to synchronize these operations a reasonable way.

Signed-off-by: Petr Mladek <pmladek@suse.com>
---
 include/linux/kthread.h |  4 ++++
 kernel/kthread.c        | 53 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 49f59b087b6b..1d5ca191562f 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -168,6 +168,10 @@ bool queue_delayed_kthread_work(struct kthread_worker *worker,
 				struct delayed_kthread_work *dwork,
 				unsigned long delay);
 
+bool mod_delayed_kthread_work(struct kthread_worker *worker,
+			      struct delayed_kthread_work *dwork,
+			      unsigned long delay);
+
 void flush_kthread_work(struct kthread_work *work);
 void flush_kthread_worker(struct kthread_worker *worker);
 
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 10129fdd4f3b..2cc32cad66ef 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -970,6 +970,59 @@ static bool __cancel_kthread_work(struct kthread_work *work, bool is_dwork,
 	return false;
 }
 
+/**
+ * mod_delayed_kthread_work - modify delay of or queue a delayed kthread work
+ * @worker: kthread worker to use
+ * @dwork: delayed kthread work to queue
+ * @delay: number of jiffies to wait before queuing
+ *
+ * If @dwork is idle, equivalent to queue_delayed_kthread work(). Otherwise,
+ * modify @dwork's timer so that it expires after @delay. If @delay is zero,
+ * @work is guaranteed to be queued immediately.
+ *
+ * Return: %true if @dwork was pending and its timer was modified,
+ * %false otherwise.
+ *
+ * A special case is when the work is being canceled in parallel.
+ * It might be caused either by the real cancel_delayed_kthread_work_sync()
+ * or yet another mod_delayed_kthread_work() call. We let the other command
+ * win and return %false here. The caller is supposed to synchronize these
+ * operations a reasonable way.
+ *
+ * This function is safe to call from any context including IRQ handler.
+ * See __cancel_kthread_work() and delayed_kthread_work_timer_fn()
+ * for details.
+ */
+bool mod_delayed_kthread_work(struct kthread_worker *worker,
+			      struct delayed_kthread_work *dwork,
+			      unsigned long delay)
+{
+	struct kthread_work *work = &dwork->work;
+	unsigned long flags;
+	int ret = false;
+
+	spin_lock_irqsave(&worker->lock, flags);
+
+	/* Do not bother with canceling when never queued. */
+	if (!work->worker)
+		goto fast_queue;
+
+	/* Work must not be used with more workers, see queue_kthread_work() */
+	WARN_ON_ONCE(work->worker != worker);
+
+	/* Do not fight with another command that is canceling this work. */
+	if (work->canceling)
+		goto out;
+
+	ret = __cancel_kthread_work(work, true, &flags);
+fast_queue:
+	__queue_delayed_kthread_work(worker, dwork, delay);
+out:
+	spin_unlock_irqrestore(&worker->lock, flags);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(mod_delayed_kthread_work);
+
 static bool __cancel_kthread_work_sync(struct kthread_work *work, bool is_dwork)
 {
 	struct kthread_worker *worker = work->worker;
-- 
1.8.5.6

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  parent reply	other threads:[~2016-04-14 15:14 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-14 15:14 [PATCH v6 00/20] kthread: Use kthread worker API more widely Petr Mladek
2016-04-14 15:14 ` [PATCH v6 01/20] kthread/smpboot: Do not park in kthread_create_on_cpu() Petr Mladek
2016-04-14 15:14 ` [PATCH v6 02/20] kthread: Allow to call __kthread_create_on_node() with va_list args Petr Mladek
2016-04-14 15:14 ` [PATCH v6 03/20] kthread: Add create_kthread_worker*() Petr Mladek
2016-04-14 15:14 ` [PATCH v6 04/20] kthread: Add drain_kthread_worker() Petr Mladek
2016-04-14 15:14 ` [PATCH v6 05/20] kthread: Add destroy_kthread_worker() Petr Mladek
2016-04-14 15:14 ` [PATCH v6 06/20] kthread: Detect when a kthread work is used by more workers Petr Mladek
2016-04-14 15:14 ` [PATCH v6 07/20] kthread: Initial support for delayed kthread work Petr Mladek
2016-04-14 15:14 ` [PATCH v6 08/20] kthread: Allow to cancel " Petr Mladek
2016-04-14 15:14 ` Petr Mladek [this message]
2016-04-14 15:14 ` [PATCH v6 10/20] kthread: Better support freezable kthread workers Petr Mladek
2016-04-14 15:14 ` [PATCH v6 11/20] mm/huge_page: Convert khugepaged() into kthread worker API Petr Mladek
2016-04-14 15:14 ` [PATCH v6 12/20] ring_buffer: Convert benchmark kthreads " Petr Mladek
2016-04-14 15:14 ` [PATCH v6 13/20] hung_task: Convert hungtaskd " Petr Mladek
2016-04-14 15:14 ` [PATCH v6 14/20] kmemleak: Convert kmemleak kthread " Petr Mladek
2016-04-14 15:14 ` [PATCH v6 15/20] ipmi: Convert kipmi " Petr Mladek
2016-04-14 15:14 ` [PATCH v6 16/20] IB/fmr_pool: Convert the cleanup thread " Petr Mladek
     [not found]   ` <1460646879-617-17-git-send-email-pmladek-IBi9RG/b67k@public.gmane.org>
2016-05-18 15:36     ` Doug Ledford
2016-04-14 15:14 ` [PATCH v6 17/20] memstick/r592: Better synchronize debug messages in r592_io kthread Petr Mladek
2016-04-14 15:14 ` [PATCH v6 18/20] memstick/r592: convert r592_io kthread into kthread worker API Petr Mladek
2016-04-14 15:14 ` [PATCH v6 19/20] thermal/intel_powerclamp: Remove duplicated code that starts the kthread Petr Mladek
2016-04-14 15:14 ` [PATCH v6 20/20] thermal/intel_powerclamp: Convert the kthread to kthread worker API Petr Mladek
2016-08-25  8:33   ` Sebastian Andrzej Siewior
2016-08-25 11:37     ` Petr Mladek
2016-08-25 11:44       ` Sebastian Andrzej Siewior
2016-04-22 18:30 ` [PATCH v6 00/20] kthread: Use kthread worker API more widely Tejun Heo
2016-05-11 10:52   ` Petr Mladek
2016-05-25 20:42     ` Tejun Heo

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