From: Rusty Russell <rusty@rustcorp.com.au>
To: Zachary Amsden <zach@vmware.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
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,
Virtualization Mailing List <virtualization@lists.osdl.org>,
Andi Kleen <ak@suse.de>
Subject: Re: [PATCH] Fix preemptible lazy mode bug
Date: Sat, 25 Aug 2007 21:57:10 +1000 [thread overview]
Message-ID: <1188043030.20041.75.camel@localhost.localdomain> (raw)
In-Reply-To: <46CE81DC.90103@vmware.com>
On Thu, 2007-08-23 at 23:59 -0700, Zachary Amsden wrote:
> Jeremy Fitzhardinge wrote:
> > Hm. Doing any kind of lazy-state operation with preemption enabled is
> > fundamentally meaningless. How does it get into a preemptable state
> >
>
> Agree 100%. It is the lazy mode flush that might happen when preempt is
> enabled, but lazy mode is disabled. In that case, the code relies on
> per-cpu variables, which is a bad thing to do in preemtible code. This
> can happen in the current code path.
Frankly, we should hoist the per-cpu state into generic paravirt code,
get rid of the FLUSH "state" and only call the lazy_mode hooks when
actually entering or exiting a lazy mode.
The only reason lguest doesn't use a per-cpu var is that guests are
currently UP only. If that were fixed, we'd have identical VMI, Xen and
lguest lazy state handing.
Cheers,
Rusty.
next prev parent reply other threads:[~2007-08-25 11:57 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <46CE70C8.2030005@vmware.com>
2007-08-24 6:53 ` [PATCH] Fix preemptible lazy mode bug Jeremy Fitzhardinge
2007-08-24 6:59 ` Zachary Amsden
2007-08-25 11:57 ` Rusty Russell [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
2007-08-24 5:46 Zachary Amsden
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