linux-kernel - Re: [PATCH] Fix preemptible lazy mode bug

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Date:	Tue, 04 Sep 2007 14:42:01 +0100
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Zachary Amsden <zach@...are.com>,
	Linus Torvalds <torvalds@...l.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>,
	Chris Wright <chrisw@...s-sol.org>, stable@...nel.org,
	Virtualization Mailing List <virtualization@...ts.osdl.org>,
	Andi Kleen <ak@...e.de>,
	Anthony Liguori <anthony@...emonkey.ws>
Subject: Re: [PATCH] Fix preemptible lazy mode bug

Rusty Russell wrote:
>  static inline void arch_flush_lazy_mmu_mode(void)
>  {
> -	PVOP_VCALL1(set_lazy_mode, PARAVIRT_LAZY_FLUSH);
> +	if (unlikely(__get_cpu_var(paravirt_lazy_mode) == PARAVIRT_LAZY_MMU))
> +		arch_leave_lazy_mmu_mode();
>  }
>   

This changes the semantics a bit; previously "flush" would flush
anything pending but leave us in lazy mode.  This just drops lazymode
altogether?

I guess if we assume that flushing is a rare event then its OK, but I
think the name's a bit misleading.  How does it differ from plain
arch_leave_lazy_mmu_mode()?

    J
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