Messages in this thread | | | Date | Tue, 1 Apr 2014 13:53:40 +0100 | From | David Vrabel <> | Subject | Re: [Xen-devel] [PATCH 4/4] xen/xenbus: Avoid synchronous wait on XenBus stalling shutdown/restart. |
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On 31/03/14 21:33, Konrad Rzeszutek Wilk wrote: > > Subject: [PATCH] xen/xenbus: Avoid synchronous wait on XenBus stalling > shutdown/restart. > > The 'read_reply' works with 'process_msg' to read of a reply in XenBus. > 'process_msg' is running from within the 'xenbus' thread. Whenever > a message shows up in XenBus it is put on a xs_state.reply_list list > and 'read_reply' picks it up. > > The problem is if the backend domain or the xenstored process is killed. > In which case 'xenbus' is still awaiting - and 'read_reply' if called - > stuck forever waiting for the reply_list to have some contents. > > This is normally not a problem - as the backend domain can come back > or the xenstored process can be restarted. However if the domain > is in process of being powered off/restarted/halted - there is no > point of waiting on it coming back - as we are effectively being > terminated and should not impede the progress. > > This patch solves this problem by checking whether the guest is > the right domain. If it is an initial domain and hurtling towards > death - there is no point of continuing the wait. All other type > of guests continue with their behavior. > mechanism a bit more asynchronous.
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
David
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