From: "Wu, Feng" <feng.wu@intel.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
"Wu, Feng" <feng.wu@intel.com>,
"george.dunlap@eu.citrix.com" <george.dunlap@eu.citrix.com>,
"andrew.cooper3@citrix.com" <andrew.cooper3@citrix.com>,
"dario.faggioli@citrix.com" <dario.faggioli@citrix.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: [PATCH v4 6/6] VMX: Fixup PI descritpor when cpu is offline
Date: Wed, 28 Sep 2016 06:53:58 +0000 [thread overview]
Message-ID: <E959C4978C3B6342920538CF579893F0198804DA@SHSMSX104.ccr.corp.intel.com> (raw)
In-Reply-To: <57E938BA020000780011275C@prv-mh.provo.novell.com>
> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: Monday, September 26, 2016 9:03 PM
> To: Wu, Feng <feng.wu@intel.com>
> Cc: andrew.cooper3@citrix.com; dario.faggioli@citrix.com;
> george.dunlap@eu.citrix.com; Tian, Kevin <kevin.tian@intel.com>; xen-
> devel@lists.xen.org
> Subject: Re: [PATCH v4 6/6] VMX: Fixup PI descritpor when cpu is offline
>
> >>> On 21.09.16 at 04:37, <feng.wu@intel.com> wrote:
> > +void vmx_pi_desc_fixup(int cpu)
> > +{
> > + unsigned int new_cpu, dest;
> > + unsigned long flags;
> > + struct arch_vmx_struct *vmx, *tmp;
> > + spinlock_t *new_lock, *old_lock = &per_cpu(vmx_pi_blocking, cpu).lock;
> > + struct list_head *blocked_vcpus = &per_cpu(vmx_pi_blocking, cpu).list;
> > +
> > + if ( !iommu_intpost )
> > + return;
> > +
> > + spin_lock_irqsave(old_lock, flags);
> > +
> > + list_for_each_entry_safe(vmx, tmp, blocked_vcpus, pi_blocking.list)
> > + {
> > + /*
> > + * We need to find an online cpu as the NDST of the PI descriptor, it
> > + * doesn't matter whether it is within the cpupool of the domain or
> > + * not. As long as it is online, the vCPU will be woken up once the
> > + * notification event arrives.
> > + */
> > + new_cpu = cpumask_any(&cpu_online_map);
> > + new_lock = &per_cpu(vmx_pi_blocking, new_cpu).lock;
> > +
> > + spin_lock(new_lock);
>
> Without extra consideration this is a classical ABBA deadlock
> scenario. Please add a comment (perhaps at the first lock location
> above) at least briefly explaining why there can't be any deadlock
> here.
Yes, I also noted this. I will add a comment here, which is really needed.
Thanks a lot!
Thanks,
Feg
>
> Apart from that the patch looks fine to me now.
>
> Jan
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel
prev parent reply other threads:[~2016-09-28 6:53 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-21 2:37 [PATCH v4 0/6] VMX: Properly handle pi descriptor and per-cpu blocking list Feng Wu
2016-09-21 2:37 ` [PATCH v4 1/6] VMX: Statically assign two PI hooks Feng Wu
2016-09-26 11:37 ` Jan Beulich
2016-09-26 12:09 ` Jan Beulich
2016-09-28 6:48 ` Wu, Feng
2016-09-28 9:38 ` Jan Beulich
2016-10-09 8:30 ` Wu, Feng
2016-10-10 7:26 ` Jan Beulich
2016-09-21 2:37 ` [PATCH v4 2/6] VMX: Properly handle pi when all the assigned devices are removed Feng Wu
2016-09-26 11:46 ` Jan Beulich
2016-09-28 6:50 ` Wu, Feng
2016-09-28 9:52 ` Jan Beulich
2016-09-29 3:08 ` Wu, Feng
2016-09-21 2:37 ` [PATCH v4 3/6] VMX: Cleanup PI per-cpu blocking list when vcpu is destroyed Feng Wu
2016-09-21 2:37 ` [PATCH v4 4/6] VMX: Make sure PI is in proper state before install the hooks Feng Wu
2016-09-26 12:45 ` Jan Beulich
2016-09-28 6:50 ` Wu, Feng
2016-09-21 2:37 ` [PATCH v4 5/6] VT-d: No need to set irq affinity for posted format IRTE Feng Wu
2016-09-26 12:58 ` Jan Beulich
2016-09-28 6:51 ` Wu, Feng
2016-09-28 9:58 ` Jan Beulich
2016-10-09 5:35 ` Wu, Feng
2016-10-10 7:02 ` Jan Beulich
2016-10-10 22:55 ` Wu, Feng
2016-09-21 2:37 ` [PATCH v4 6/6] VMX: Fixup PI descritpor when cpu is offline Feng Wu
2016-09-26 13:03 ` Jan Beulich
2016-09-28 6:53 ` Wu, Feng [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=E959C4978C3B6342920538CF579893F0198804DA@SHSMSX104.ccr.corp.intel.com \
--to=feng.wu@intel.com \
--cc=JBeulich@suse.com \
--cc=andrew.cooper3@citrix.com \
--cc=dario.faggioli@citrix.com \
--cc=george.dunlap@eu.citrix.com \
--cc=kevin.tian@intel.com \
--cc=xen-devel@lists.xen.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).