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Re: [Qemu-devel] [RFC PATCH v4 14/15] slirp: handle race condition
From: |
Jan Kiszka |
Subject: |
Re: [Qemu-devel] [RFC PATCH v4 14/15] slirp: handle race condition |
Date: |
Fri, 19 Apr 2013 10:21:19 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
On 2013-04-19 02:18, liu ping fan wrote:
> On Thu, Apr 18, 2013 at 3:13 PM, Jan Kiszka <address@hidden> wrote:
>> On 2013-04-17 10:39, Liu Ping Fan wrote:
>>> From: Liu Ping Fan <address@hidden>
>>>
>>> Slirp and its peer can run on different context at the same time.
>>> Using lock to protect
>>
>> What are the usage rules for this lock, what precisely is it protecting?
>> Is it ensured that we do not take the BQL while holding this one?
>>
> It protect the slirp state, since slirp can be touched by slrip_input
> called by frontend(ex, e1000), also it can be touched by its event
> handler. With this lock, we do not need BQL
...but the BQL will, at least initially, remain to be everywhere. Every
non-converted device model will hold it while calling into Slirp. So we
have the ordering "BQL before Slirp lock" already. And we must ensure
that there is no "BQL after Slirp lock". Can you guarantee this?
Jan
--
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux
- [Qemu-devel] [RFC PATCH v4 08/15] net: hub use lock to protect ports list, (continued)
- [Qemu-devel] [RFC PATCH v4 08/15] net: hub use lock to protect ports list, Liu Ping Fan, 2013/04/17
- [Qemu-devel] [RFC PATCH v4 09/15] net: introduce lock to protect NetQueue, Liu Ping Fan, 2013/04/17
- [Qemu-devel] [RFC PATCH v4 10/15] net: introduce lock to protect NetClientState's peer's access, Liu Ping Fan, 2013/04/17
- [Qemu-devel] [RFC PATCH v4 11/15] net: make netclient re-entrant with refcnt, Liu Ping Fan, 2013/04/17
- [Qemu-devel] [RFC PATCH v4 12/15] slirp: make timeout local, Liu Ping Fan, 2013/04/17
- [Qemu-devel] [RFC PATCH v4 13/15] slirp: make slirp event dispatch based on slirp instance, not global, Liu Ping Fan, 2013/04/17
- [Qemu-devel] [RFC PATCH v4 14/15] slirp: handle race condition, Liu Ping Fan, 2013/04/17
[Qemu-devel] [RFC PATCH v4 15/15] slirp: use lock to protect the slirp_instances, Liu Ping Fan, 2013/04/17