[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v1 03/10] libxl: store a copy of vanilla domain configuration when creating domain
Wei Liu writes ("Re: [PATCH v1 03/10] libxl: store a copy of vanilla domain configuration when creating domain"): > On Fri, Jul 25, 2014 at 04:01:06PM +0100, Ian Jackson wrote: > > During that time various operations would block unreasonably. > > That's a bit unfortunate. But what can we do to close that window? > I think no good will come out if I try to fiddle with domain state > during creation anyway, so locking like this may be acceptable? No, because it might block a management daemon. You're not allowed to hold a lock which libxl operations will block on while doing anything `slow' in the ao sense. Conceivably in a sufficiently complicated system it might even result in deadlock. I think the right answer is for those attempts to fiddle with the domain state to fail. > > Also, I think you mustn't use an fcntl lock across ao operation > > callback chains. fcntl locks do not exclude other threads in the same > > process. > > Then we need both mutex and file lock? Mutex to protect against threads > in the same process while file lock protect against other processes. I think the answer is that you have to not retain the lock for so long. Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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