linux-kernel - [PATCH] oprofile, hrtimer: only add samples if regs are available

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Date:	Wed, 28 Apr 2010 21:24:09 +0200
From:	Robert Richter <robert.richter@....com>
To:	Siarhei Siamashka <siarhei.siamashka@...ia.com>
CC:	oprofile-list@...ts.sourceforge.net,
	"Carmody Phil.2 (EXT-Ixonos/Helsinki)" <ext-phil.2.carmody@...ia.com>,
	"schwidefsky@...ibm.com" <schwidefsky@...ibm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] oprofile, hrtimer: only add samples if regs are available

On 28.04.10 18:59:06, Robert Richter wrote:
> On 27.04.10 20:47:51, Siarhei Siamashka wrote:
> > Isn't hrtimer callback function supposed to be only called from IRQ context
> > after this cleanup: http://lwn.net/Articles/308545/ ?
> 
> Yes, the patch is upstream since v2.6.29. Thanks Siarhei.
> 
> I will add a null pointer check anyway.

--

>From ad8a6546b32d22ecf92b4448ad329133d18dde0f Mon Sep 17 00:00:00 2001
From: Robert Richter <robert.richter@....com>
Date: Wed, 28 Apr 2010 20:43:18 +0200
Subject: [PATCH] oprofile, hrtimer: only add samples if regs are available

This patch adds a check if the regs pointer is valid. This actually
should not happen since hrtimer notification code should always run in
hard_irq context after this commit (since v2.6.29):

 ca10949 hrtimer: removing all ur callback modes

However, if code does not run in interrupt context, regs will be null:

 http://www.mail-archive.com/linux-omap@vger.kernel.org/msg14074.html

Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Robert Richter <robert.richter@....com>
---
 drivers/oprofile/timer_int.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/drivers/oprofile/timer_int.c b/drivers/oprofile/timer_int.c
index dc0ae4d..ca3436c 100644
--- a/drivers/oprofile/timer_int.c
+++ b/drivers/oprofile/timer_int.c
@@ -24,8 +24,12 @@ static DEFINE_PER_CPU(struct hrtimer, oprofile_hrtimer);
 
 static enum hrtimer_restart oprofile_hrtimer_notify(struct hrtimer *hrtimer)
 {
-	oprofile_add_sample(get_irq_regs(), 0);
+	struct pt_regs *regs = get_irq_regs();
+
+	if (regs)
+		oprofile_add_sample(regs, 0);
 	hrtimer_forward_now(hrtimer, ns_to_ktime(TICK_NSEC));
+
 	return HRTIMER_RESTART;
 }
 
-- 
1.7.0.3



-- 
Advanced Micro Devices, Inc.
Operating System Research Center
email: robert.richter@....com

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