From: LAPLACE Cyprien <cyprien.laplace@trango-systems.com>
To: virtualization@lists.linux-foundation.org
Cc: Linux Kernel <linux-kernel@vger.kernel.org>,
Jeremy Fitzhardinge <jeremy@goop.org>
Subject: SMP lockup in virtualized environment
Date: Tue, 24 Apr 2007 19:45:07 +0200 [thread overview]
Message-ID: <462E4223.1050109@trango-systems.com> (raw)
In a previous mail, Jeremy Fitzhardinge wrote:
> The softlockup watchdog is currently a nuisance in a virtual machine,
> since the whole system could have the CPU stolen from it for a long
> period of time. While it would be unlikely for a guest domain to be
> denied timer interrupts for over 10s, it could happen and any
> softlockup message would be completely spurious.
I wonder how the guest domain can be denied timer interrupts for such a
long time ? The only reason I see is that the guest domain is not
scheduled at all (host domain or another higher priority guest running).
Now in SMP host and guest, what happens if a guest CPU is not scheduled
for a while ?
An example: in kernel/pid.c:alloc_pid(), if one of the guest CPUs is
descheduled when holding the pidmap_lock, what happens to the other
guest CPUs who want to alloc/free pids ? Are they blocked too ?
--
Cyprien Laplace
next reply other threads:[~2007-04-24 17:45 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-24 17:45 LAPLACE Cyprien [this message]
2007-04-24 18:04 ` SMP lockup in virtualized environment Jeremy Fitzhardinge
2007-04-24 22:37 ` Chris Snook
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