Re: [Xen-devel] [PATCH for Xen 4.5 v2 2/2] xen: serialize vcpu data in sched_rt.c

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 11/10/2014 04:04 PM, Meng Xu wrote:

2014-11-10 10:40 GMT-05:00 George Dunlap <george.dunlap@xxxxxxxxxxxxx>:

On 11/10/2014 03:29 PM, Meng Xu wrote:

I'm not sure if I should resend the patch just to change the commit log and add the reason of why doing this.Â

I want to first add the reason. If I should resend the patch set, please let me know.Â

2014-11-10 7:53 GMT-05:00 George Dunlap <george.dunlap@xxxxxxxxxxxxx>:

On 10/25/2014 03:16 PM, Meng Xu wrote:

Move call to rt_update_deadline from _alloc to _insert;

The runq queue lock is not grabbed when Âârt_update_deadline is called inÂrt_alloc_vdata function, which may cause race condition.

Can you not grab the lock in rt_alloc_vdata?Â

âYes. Because when we allocate a rt_vcpu, only one cpu will do that. In addition, before the rt_vcpu is inserted into the runq, we won't have more than one cpu operate on this rt_vcpu.â

Right, well that's important information to help someone reading the patch understand what's going on.

Thanks for being flexible. :-)

Â-George

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