linux-kernel - [RFC 1/7] hrtimer: Warn if hrtimer_start*() failed to enqueue hrtimer

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Message-Id: <bc8cabd00810c2f91cb45a64514f5c4ca12d584c.1404888801.git.viresh.kumar@linaro.org>
Date:	Wed,  9 Jul 2014 12:25:33 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	tglx@...utronix.de
Cc:	linaro-kernel@...ts.linaro.org, linux-kernel@...r.kernel.org,
	fweisbec@...il.com, arvind.chauhan@....com,
	preeti@...ux.vnet.ibm.com, khilman@...aro.org,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: [RFC 1/7] hrtimer: Warn if hrtimer_start*() failed to enqueue hrtimer

hrtimer_start*() family never fails to enqueue a hrtimer to a clock-base. The
only special case is when the hrtimer was in past. If it is getting enqueued to
local CPUs's clock-base, we raise a softirq and exit, else we handle that on
next interrupt on remote CPU.

At several places in kernel we check if hrtimer is enqueued properly with
hrtimer_active(). This isn't required and can be dropped.

Before fixing that, lets make sure hrtimer is always enqueued properly by adding

	WARN_ON_ONCE(!hrtimer_active(timer));

towards the end of __hrtimer_start_range_ns().

Suggested-by: Frederic Weisbecker <fweisbec@...il.com>
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 kernel/hrtimer.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 3ab2899..cf40209 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1037,6 +1037,8 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
 
 	unlock_hrtimer_base(timer, &flags);
 
+	/* Make sure timer is enqueued */
+	WARN_ON_ONCE(!hrtimer_active(timer));
 	return ret;
 }
 EXPORT_SYMBOL_GPL(__hrtimer_start_range_ns);
-- 
2.0.0.rc2

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