linux-kernel - tick issue: tick_setup

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Date:	Sat, 2 Jul 2011 10:12:42 +0800
From:	chao xie <xiechao.linux@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: tick issue: tick_setup_device()

hi
I am very strange about this function.
In this function, it has
/*
        * When the device is not per cpu, pin the interrupt to the
        * current cpu:
        */
       if (!cpumask_equal(newdev->cpumask, cpumask))
               irq_set_affinity(newdev->irq, cpumask);

When the clock event device has cpu_mask set to be cpumask_of(1), it
means that the device is bound to cpu1. So above code has covered it,
but why we have "!cpumask_equal(newdev->cpumask, cpumask)"?
if the "newdev->cpumask" equals "cpumask", cpumask_equal will return
1, and at this situation we will set the irq affinity because the
device is bound to the dedicated cpu.

Is there a bug, or i understand wrong about cpumask of clock_event_device?
Thanks.
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