Messages in this thread | | | From | "Skidanov, Alexey" <> | Subject | RE: CONFIG_PREEMPT_COUNT | Date | Mon, 31 Mar 2014 12:50:30 +0000 |
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Paul, Thank you for your answer. We have PREEMT_VOLUNTARY defined, so that is the reason why the CONFIG_PREEMPT_COUNT is undefined. The second question (that was badly formatted in original message) was:
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” ?
-----Original Message----- From: Paul Bolle [mailto:pebolle@tiscali.nl] Sent: Monday, March 31, 2014 3:25 PM To: Skidanov, Alexey Cc: linux-kernel@vger.kernel.org; Gabbay, Oded Subject: Re: CONFIG_PREEMPT_COUNT
Alexey,
On Mon, 2014-03-31 at 10:38 +0000, Skidanov, Alexey wrote: > What is the purpose of CONFIG_PREEMPT_COUNT define and how I can > define it?
CONFIG_PREEMPT_COUNT is a Kconfig macro, ie it's (in short) to be defined as a result one of the "*config" make targets. And doing git grep -nw PREEMPT_COUNT
gives kernel/Kconfig.preempt:38: select PREEMPT_COUNT kernel/Kconfig.preempt:57:config PREEMPT_COUNT lib/Kconfig.debug:964: select PREEMPT_COUNT
And looking at those hits it seems PREEMPT_COUNT will be set, and therefore CONFIG_PREEMPT_COUNT defined, if either PREEMPT or DEBUG_ATOMIC_SLEEP are set in a .config.
(I'm not familiar with PREEMPT_COUNT. I think I never used it.)
Hope this helps,
Paul Bolle
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