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SubjectRe: [PATCH] Fix preemptible lazy mode bug
Zachary Amsden wrote:
> Do you agree it is better to be safe than sorry in this case? The
> kind of bugs introduced by getting this wrong are really hard to find,
> and I would rather err on the side of an extra increment and decrement
> of preempt_count that causing a regression.

I think this patch is the direction we should go. I this this would
work equally well for the other pv implementations; it would probably go
into the common lazy mode logic when we get around to doing it.

J

diff -r b3fcc228c531 arch/i386/xen/enlighten.c
--- a/arch/i386/xen/enlighten.c Mon Aug 20 14:20:15 2007 -0700
+++ b/arch/i386/xen/enlighten.c Mon Aug 27 13:40:24 2007 -0700
@@ -250,6 +250,9 @@ static void xen_halt(void)

static void xen_set_lazy_mode(enum paravirt_lazy_mode mode)
{
+ if (preemptible() && mode == PARAVIRT_LAZY_FLUSH)
+ return; /* nothing to flush with preempt on */
+
BUG_ON(preemptible());

switch (mode) {

-
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