linux-kernel - [Query] tick-oneshot: Why do we need to disable interrupts for reading tick_cpu

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Message-ID: <CAKohpo=6RGy1vVZ58N6yH-sfUFPs3afZLj88MtuarYCFJ=Y0PQ@mail.gmail.com>
Date:	Mon, 7 Apr 2014 17:28:46 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Linaro Networking <linaro-networking@...aro.org>
Subject: [Query] tick-oneshot: Why do we need to disable interrupts for
 reading tick_cpu_device.mode

Hi Thomas,

I found this piece of code in tick-oneshot.c:

+int tick_oneshot_mode_active(void)
+{
+       unsigned long flags;
+       int ret;
+
+       local_irq_save(flags);
+       ret = __get_cpu_var(tick_cpu_device).mode == TICKDEV_MODE_ONESHOT;
+       local_irq_restore(flags);
+
+       return ret;
+}

Why do we need local_irq_save/restore() here for just reading value
of this variable? Can these be dropped? If yes, I would do that as
part of my cleanup series around tick stuff.

--
viresh
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