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Message-ID: <AD975D71AAD7784D8D1265DF6444C2FD0132AD51@storexdag03.amd.com>
Date:	Mon, 31 Mar 2014 10:38:12 +0000
From:	"Skidanov, Alexey" <Alexey.Skidanov@....com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	"Gabbay, Oded" <Oded.Gabbay@....com>
Subject: CONFIG_PREEMPT_COUNT

Hello,

I found that preempt_enable() and preempt_disable() macros are defined differently depending on CONFIG_PREEMPT_COUNT:
- They increment per CPU preemption counter, if CONFIG_PREEMPT_COUNT defined
- They do nothing (just call barrier), if not.
I have it undefined in my source tree.

The questions are:
1. What is the purpose of CONFIG_PREEMPT_COUNT define and how I can define it?
2. In the previous kernel versions, spin_lock() and spin_unlock() call preempt_enable() and preempt_disable() respectively, ensuring that the current task will not be preempted by any other task while lock is held. Is this still ensured with these macros defined as "do nothing" ?

Thanks
Alexey

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