linux-kernel - Question reg. asm/qrwlock.h

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Message-ID: <CAJhHMCCDPe_GGDWUF3OHQieCKLty2+TaYZwnKjK9ZF3z0auo8A@mail.gmail.com>
Date:	Fri, 5 Sep 2014 19:45:31 -0400
From:	Pranith Kumar <bobby.prani@...il.com>
To:	Waiman.Long@...com, LKML <linux-kernel@...r.kernel.org>
Subject: Question reg. asm/qrwlock.h

Hi Waiman,

I see that in arch/x86/include/asm/qrwlock.h, there is this snippet within

#ifndef CONFIG_X86_PPRO_FENCE
#define queue_write_unlock queue_write_unlock
static inline void queue_write_unlock(struct qrwlock *lock)
{
        barrier();
        ACCESS_ONCE(*(u8 *)&lock->cnts) = 0;
}
#endif

I've been trying to understand why this special case is necessary for
PPRO. Could you please explain?

Thanks!
-- 
Pranith
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