linux-kernel - [tip:timers/urgent] hrtimers: Notify hrtimer users of switches to NOHZ mode

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Message-ID: <tip-2d0640b47da74cff7c11642c798d40de861ed524@git.kernel.org>
Date:	Wed, 19 Jan 2011 19:09:52 GMT
From:	tip-bot for Stephen Boyd <sboyd@...eaurora.org>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, sboyd@...eaurora.org,
	mingo@...e.hu
Subject: [tip:timers/urgent] hrtimers: Notify hrtimer users of switches to NOHZ mode

Commit-ID:  2d0640b47da74cff7c11642c798d40de861ed524
Gitweb:     http://git.kernel.org/tip/2d0640b47da74cff7c11642c798d40de861ed524
Author:     Stephen Boyd <sboyd@...eaurora.org>
AuthorDate: Tue, 18 Jan 2011 22:46:34 -0800
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 19 Jan 2011 20:08:15 +0100

hrtimers: Notify hrtimer users of switches to NOHZ mode

When NOHZ=y and high res timers are disabled (via cmdline or
Kconfig) tick_nohz_switch_to_nohz() will notify the user about
switching into NOHZ mode. Nothing is printed for the case where
HIGH_RES_TIMERS=y. Fix this for the HIGH_RES_TIMERS=y case by
duplicating the printk from the low res NOHZ path in the high
res NOHZ path.

This confused me since I was thinking 'dmesg | grep -i NOHZ' would
tell me if NOHZ was enabled, but if I have hrtimers there is
nothing.

Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
Acked-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
LKML-Reference: <1295419594-13085-1-git-send-email-sboyd@...eaurora.org>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/time/tick-sched.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 3e216e0..c55ea24 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -642,8 +642,7 @@ static void tick_nohz_switch_to_nohz(void)
 	}
 	local_irq_enable();
 
-	printk(KERN_INFO "Switched to NOHz mode on CPU #%d\n",
-	       smp_processor_id());
+	printk(KERN_INFO "Switched to NOHz mode on CPU #%d\n", smp_processor_id());
 }
 
 /*
@@ -795,8 +794,10 @@ void tick_setup_sched_timer(void)
 	}
 
 #ifdef CONFIG_NO_HZ
-	if (tick_nohz_enabled)
+	if (tick_nohz_enabled) {
 		ts->nohz_mode = NOHZ_MODE_HIGHRES;
+		printk(KERN_INFO "Switched to NOHz mode on CPU #%d\n", smp_processor_id());
+	}
 #endif
 }
 #endif /* HIGH_RES_TIMERS */
--
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