Re: Xen 4.7 crash

[Wei Liu <wei.liu2@citrix.com>]

On Tue, Jun 14, 2016 at 09:11:47AM -0400, Aaron Cornelius wrote:
> On 6/9/2016 7:14 AM, Ian Jackson wrote:
> >Aaron Cornelius writes ("Re: [Xen-devel] Xen 4.7 crash"):
> >>I am not that familiar with the xenstored code, but as far as I can tell
> >>the grant mapping will be held by the xenstore until the xs_release()
> >>function is called (which is not called by libxl, and I do not
> >>explicitly call it in my software, although I might now just to be
> >>safe), or until the last reference to a domain is released and the
> >>registered destructor (destroy_domain), set by talloc_set_destructor(),
> >>is called.
> >
> >I'm not sure I follow.  Or maybe I disagree.  ISTM that:
> >
> >The grant mapping is released by destroy_domain, which is called via
> >the talloc destructor as a result of talloc_free(domain->conn) in
> >domain_cleanup.  I don't see other references to domain->conn.
> >
> >domain_cleanup calls talloc_free on domain->conn when it sees the
> >domain marked as dying in domain_cleanup.
> >
> >So I still think that your acl reference ought not to keep the grant
> >mapping alive.
> 
> It took a while to complete the testing, but we've finished trying to
> reproduce the error using oxenstored instead of the C xenstored.  When the
> condition occurs that caused the error with the C xenstored (on
> 4.7.0-rc4/8478c9409a2c6726208e8dbc9f3e455b76725a33), oxenstored does not
> cause the crash.
> 
> So for whatever reason, it would appear that the C xenstored does keep the
> grant allocations open, but oxenstored does not.
> 

Can you provide some easy to follow steps to reproduce this issue?

AFAICT your environment is very specialised, but we should be able to
trigger the issue with plan xenstore-* utilities?

Wei.

> - Aaron Cornelius
> 

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