xen-devel
[Xen-devel] Re: [PATCH 10/13] xen/pvticket: allow interrupts to be enabl
To: |
Peter Zijlstra <peterz@xxxxxxxxxxxxx> |
Subject: |
[Xen-devel] Re: [PATCH 10/13] xen/pvticket: allow interrupts to be enabled while blocking |
From: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
Date: |
Fri, 02 Sep 2011 12:30:29 -0700 |
Cc: |
Marcelo Tosatti <mtosatti@xxxxxxxxxx>, Nick Piggin <npiggin@xxxxxxxxx>, KVM <kvm@xxxxxxxxxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Andi Kleen <andi@xxxxxxxxxxxxxx>, Avi Kivity <avi@xxxxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Ingo Molnar <mingo@xxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx> |
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Fri, 02 Sep 2011 12:31:15 -0700 |
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On 09/02/2011 07:48 AM, Peter Zijlstra wrote:
> On Thu, 2011-09-01 at 17:55 -0700, Jeremy Fitzhardinge wrote:
>> + /* Make sure an interrupt handler can't upset things in a
>> + partially setup state. */
>> local_irq_save(flags);
>>
>> + /*
>> + * We don't really care if we're overwriting some other
>> + * (lock,want) pair, as that would mean that we're currently
>> + * in an interrupt context, and the outer context had
>> + * interrupts enabled. That has already kicked the VCPU out
>> + * of xen_poll_irq(), so it will just return spuriously and
>> + * retry with newly setup (lock,want).
>> + *
>> + * The ordering protocol on this is that the "lock" pointer
>> + * may only be set non-NULL if the "want" ticket is correct.
>> + * If we're updating "want", we must first clear "lock".
>> + */
>> + w->lock = NULL;
> I mean, I don't much care about Xen code, but that's two different
> comment styles.
Yeah, that's the "two line comment style" next to "big block comment"
style - but you're right they look pretty bad juxtaposed like that.
J
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