From: Paolo Bonzini <pbonzini@redhat.com>
To: liu ping fan <qemulist@gmail.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Avi Kivity <avi@redhat.com>,
Anthony Liguori <anthony@codemonkey.ws>,
qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock
Date: Wed, 19 Sep 2012 11:14:53 +0200 [thread overview]
Message-ID: <50598D0D.2090608@redhat.com> (raw)
In-Reply-To: <CAJnKYQkGkQ+8Y3R7Z9gJmMFhPen9ygD01aMwPxmMoVcGOHws5g@mail.gmail.com>
Il 19/09/2012 11:11, liu ping fan ha scritto:
>> > Why not? devA will drop its local lock, devX will retake the big lock
>> > recursively, devB will take its local lock. In the end, we have biglock
>> > -> devB.
>> >
> But when adopting local lock, we assume take local lock, then biglock.
No, because the local lock will be dropped before taking the biglock.
The order must always be coarse->fine.
I don't know if the front-end (device) lock should come before or after
the back-end (e.g. netdev) lock in the hierarchy, but that's another story.
Paolo
> Otherwise another thread will take biglock then local lock, which
> cause the possibility of deadlock.
>
next prev parent reply other threads:[~2012-09-19 9:15 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-19 3:02 [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock liu ping fan
2012-09-19 8:06 ` Avi Kivity
2012-09-19 9:00 ` liu ping fan
2012-09-19 9:07 ` Avi Kivity
2012-09-19 9:11 ` liu ping fan
2012-09-19 9:14 ` Paolo Bonzini [this message]
2012-09-19 9:19 ` liu ping fan
2012-09-19 9:23 ` Avi Kivity
2012-09-19 9:27 ` Jan Kiszka
2012-09-19 9:28 ` Jan Kiszka
2012-09-20 7:51 ` liu ping fan
2012-09-20 7:54 ` Paolo Bonzini
2012-09-20 8:09 ` liu ping fan
2012-09-20 8:27 ` Paolo Bonzini
2012-09-20 9:07 ` Avi Kivity
2012-09-21 7:27 ` liu ping fan
2012-09-21 8:21 ` Paolo Bonzini
2012-09-19 9:21 ` Avi Kivity
2012-09-19 9:51 ` Paolo Bonzini
2012-09-19 10:06 ` Avi Kivity
2012-09-19 10:19 ` Paolo Bonzini
2012-09-19 10:27 ` Avi Kivity
2012-09-19 9:34 ` Jan Kiszka
2012-09-19 9:50 ` Avi Kivity
2012-09-19 10:18 ` Jan Kiszka
2012-09-24 6:33 ` liu ping fan
2012-09-24 7:44 ` Avi Kivity
2012-09-24 8:32 ` liu ping fan
2012-09-24 9:42 ` Avi Kivity
2012-09-27 3:13 ` liu ping fan
2012-09-27 9:16 ` Avi Kivity
2012-09-27 9:29 ` Paolo Bonzini
2012-09-27 9:34 ` Avi Kivity
2012-09-27 9:36 ` Paolo Bonzini
2012-09-27 10:08 ` Avi Kivity
2012-09-27 10:22 ` Paolo Bonzini
2012-09-27 10:48 ` Avi Kivity
2012-09-29 9:20 ` liu ping fan
2012-09-30 8:13 ` Avi Kivity
2012-09-30 8:48 ` liu ping fan
2012-09-30 11:18 ` Avi Kivity
2012-09-30 11:04 ` Blue Swirl
2012-09-30 11:17 ` Avi Kivity
2012-09-30 11:48 ` Blue Swirl
2012-09-20 8:11 ` liu ping fan
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