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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
	Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: [PATCH 5/5] hrtimer: fixup comments
Date: Mon, 05 Jan 2009 11:28:23 +0100	[thread overview]
Message-ID: <20090105103136.564276999@chello.nl> (raw)
In-Reply-To: 20090105102818.829119334@chello.nl

[-- Attachment #1: hrtimers-comments.patch --]
[-- Type: text/plain, Size: 1876 bytes --]

From: Thomas Gleixner <tglx@linutronix.de>

Clean up the comments

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 kernel/hrtimer.c |   20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

Index: linux-2.6/kernel/hrtimer.c
===================================================================
--- linux-2.6.orig/kernel/hrtimer.c
+++ linux-2.6/kernel/hrtimer.c
@@ -1141,9 +1141,9 @@ static void __run_hrtimer(struct hrtimer
 	spin_lock(&cpu_base->lock);
 
 	/*
-	 * Note: We clear the CALLBACK bit after enqueue_hrtimer to avoid
-	 * reprogramming of the event hardware. This happens at the end of this
-	 * function anyway.
+	 * Note: We clear the CALLBACK bit after enqueue_hrtimer and
+	 * we do not reprogramm the event hardware. Happens either in
+	 * hrtimer_start_range_ns() or in hrtimer_interrupt()
 	 */
 	if (restart != HRTIMER_NORESTART) {
 		BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
@@ -1540,14 +1540,12 @@ static void migrate_hrtimer_list(struct 
 		__remove_hrtimer(timer, old_base, HRTIMER_STATE_MIGRATE, 0);
 		timer->base = new_base;
 		/*
-		 * Enqueue the timers on the new cpu, but do not reprogram 
-		 * the timer as that would enable a deadlock between
-		 * hrtimer_enqueue_reprogramm() running the timer and us still
-		 * holding a nested base lock.
-		 *
-		 * Instead we tickle the hrtimer interrupt after the migration
-		 * is done, which will run all expired timers and re-programm
-		 * the timer device.
+		 * Enqueue the timers on the new cpu. This does not
+		 * reprogram the event device in case the timer
+		 * expires before the earliest on this CPU, but we run
+		 * hrtimer_interrupt after we migrated everything to
+		 * sort out already expired timers and reprogram the
+		 * event device.
 		 */
 		enqueue_hrtimer(timer, new_base);
 

-- 


  parent reply	other threads:[~2009-01-05 11:43 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-01-05 10:28 [PATCH 0/5] hrtimer: cleanups and fixes Peter Zijlstra
2009-01-05 10:28 ` [PATCH 1/5] hrtimer: splitout peek ahead functionality Peter Zijlstra
2009-01-05 10:28 ` [PATCH 2/5] hrtimer: fix HOTPLUG_CPU=n compile warning Peter Zijlstra
2009-01-05 10:28 ` [PATCH 3/5] hrtimer: simplify hotplug migration Peter Zijlstra
2009-01-05 10:28 ` [PATCH 4/5] hrtimer: fix recursion deadlock by re-introducing the softirq Peter Zijlstra
2009-01-05 10:28 ` Peter Zijlstra [this message]
2009-01-05 12:15 ` [PATCH 0/5] hrtimer: cleanups and fixes Ingo Molnar
2009-01-05 13:13   ` [PATCH] hrtimer: splitout peek ahead functionality, fix Ingo Molnar

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