From: Jan Beulich <jbeulich@suse.com>
To: Tamas K Lengyel <tamas@tklengyel.com>
Cc: "Julien Grall" <julien@xen.org>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Tamas K Lengyel" <tamas.lengyel@intel.com>,
"Wei Liu" <wl@xen.org>,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"Ian Jackson" <ian.jackson@eu.citrix.com>,
"George Dunlap" <george.dunlap@citrix.com>,
Xen-devel <xen-devel@lists.xenproject.org>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH v12 2/3] x86/mem_sharing: reset a fork
Date: Thu, 26 Mar 2020 15:52:35 +0100 [thread overview]
Message-ID: <9c7d7147-cb83-5e91-38b7-906a81582ac4@suse.com> (raw)
In-Reply-To: <CABfawhkRpvV0asinjdBx2qMq-RQOBbx13bENREszzkBhrgS71Q@mail.gmail.com>
On 26.03.2020 15:48, Tamas K Lengyel wrote:
> On Thu, Mar 26, 2020 at 4:17 AM Jan Beulich <jbeulich@suse.com> wrote:
>>
>> On 23.03.2020 18:04, Tamas K Lengyel wrote:
>>> +static int mem_sharing_fork_reset(struct domain *d, struct domain *pd)
>>> +{
>>> + int rc;
>>> + struct p2m_domain *p2m = p2m_get_hostp2m(d);
>>> + struct page_info *page, *tmp;
>>> +
>>> + spin_lock(&d->page_alloc_lock);
>>> + domain_pause(d);
>>
>> Why do you take the lock first?
>
> No particular reason - does the order matter?
I think you'd better avoid holding a lock for extended periods
of time. And what's perhaps worse, what if a vCPU of the domain
sits in Xen trying to acquire this lock - you'd deadlock trying
to pause the domain then.
Jan
next prev parent reply other threads:[~2020-03-26 14:52 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-23 17:04 [Xen-devel] [PATCH v12 0/3] VM forking Tamas K Lengyel
2020-03-23 17:04 ` [Xen-devel] [PATCH v12 1/3] xen/mem_sharing: " Tamas K Lengyel
2020-03-25 15:47 ` Roger Pau Monné
2020-03-25 16:04 ` Tamas K Lengyel
2020-03-25 16:16 ` Tamas K Lengyel
2020-03-25 16:34 ` Tamas K Lengyel
2020-03-25 16:42 ` Julien Grall
2020-03-25 16:47 ` Tamas K Lengyel
2020-03-25 16:51 ` Julien Grall
2020-03-25 17:00 ` Tamas K Lengyel
2020-03-25 17:16 ` Roger Pau Monné
2020-03-25 17:47 ` Tamas K Lengyel
2020-03-25 16:54 ` Roger Pau Monné
2020-03-26 7:02 ` Jan Beulich
2020-03-26 8:42 ` Roger Pau Monné
2020-03-26 7:07 ` Jan Beulich
2020-03-26 9:10 ` Roger Pau Monné
2020-03-26 17:01 ` Tamas K Lengyel
2020-03-26 12:33 ` Jan Beulich
2020-03-26 14:52 ` Tamas K Lengyel
2020-03-23 17:04 ` [Xen-devel] [PATCH v12 2/3] x86/mem_sharing: reset a fork Tamas K Lengyel
2020-03-25 15:52 ` Roger Pau Monné
2020-03-25 15:54 ` Tamas K Lengyel
2020-03-26 10:16 ` Jan Beulich
2020-03-26 14:48 ` Tamas K Lengyel
2020-03-26 14:52 ` Jan Beulich [this message]
2020-03-26 14:53 ` Tamas K Lengyel
2020-03-26 23:40 ` Tamas K Lengyel
2020-03-23 17:04 ` [Xen-devel] [PATCH v12 3/3] xen/tools: VM forking toolstack side Tamas K Lengyel
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