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From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Zachary Amsden <zach@vmware.com>
Cc: Linus Torvalds <torvalds@osdl.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@osdl.org>, Chris Wright <chrisw@sous-sol.org>,
	stable@kernel.org, Rusty Russell <rusty@rustcorp.com.au>,
	Virtualization Mailing List <virtualization@lists.osdl.org>,
	Andi Kleen <ak@suse.de>Linux Kernel Mailing List
	<linux-kernel@vger.kernel.org>,
	Anthony Liguori <anthony@codemonkey.ws>
Subject: Re: [PATCH] Fix preemptible lazy mode bug
Date: Sat, 01 Sep 2007 14:09:43 -0700	[thread overview]
Message-ID: <46D9D517.6010201@goop.org> (raw)
In-Reply-To: <46CE81DC.90103@vmware.com>

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) {

WARNING: multiple messages have this Message-ID (diff)
From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Zachary Amsden <zach@vmware.com>
Cc: Linus Torvalds <torvalds@osdl.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@osdl.org>, Chris Wright <chrisw@sous-sol.org>,
	stable@kernel.org, Rusty Russell <rusty@rustcorp.com.au>,
	Virtualization Mailing List <virtualization@lists.osdl.org>,
	Andi Kleen <ak@suse.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Anthony Liguori <anthony@codemonkey.ws>
Subject: Re: [PATCH] Fix preemptible lazy mode bug
Date: Sat, 01 Sep 2007 14:09:43 -0700	[thread overview]
Message-ID: <46D9D517.6010201@goop.org> (raw)
In-Reply-To: <46CE81DC.90103@vmware.com>

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) {



  parent reply	other threads:[~2007-09-01 21:09 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-08-24  5:46 [PATCH] Fix preemptible lazy mode bug Zachary Amsden
2007-08-24  6:53 ` Jeremy Fitzhardinge
2007-08-24  6:59   ` Zachary Amsden
2007-08-25 11:57     ` Rusty Russell
2007-09-01 21:09     ` Jeremy Fitzhardinge [this message]
2007-09-01 21:09       ` Jeremy Fitzhardinge
2007-09-03 20:14       ` Rusty Russell
2007-09-04 13:42         ` Jeremy Fitzhardinge
2007-09-05 16:33           ` Rusty Russell
2007-09-05 17:05             ` Zachary Amsden
2007-09-05 17:48               ` Rusty Russell
2007-09-05 20:10             ` Jeremy Fitzhardinge
2007-09-05 20:37 ` Rusty Russell
2007-09-05 23:49   ` Zachary Amsden
2007-09-06  5:41     ` Andi Kleen
2007-09-06  9:56       ` Jeremy Fitzhardinge
2007-09-06  9:57       ` Jeremy Fitzhardinge
  -- strict thread matches above, loose matches on Subject: below --
2007-08-24  5:46 Zachary Amsden

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