Re: [Xen-devel] [PATCH 00/12] libxl: fork: SIGCHLD flexibility

[Jim Fehlig <jfehlig@xxxxxxxx>]

Ian Jackson wrote:
> Jim Fehlig writes ("Re: [Xen-devel] [PATCH 00/12] libxl: fork: SIGCHLD 
> flexibility"):
>   
>> It appears the timeout_modify callback is invoked on a previously
>> deregistered timeout.  I didn't notice the segfault when running
>> libvirtd under valgrind, but did see
>>     
>
> Hmmm.  This could be a libxl problem.  I'll review the code again and
> maybe think about adding some assertions.
>   

BTW, I only see the crash when the save/restore script is running.  I
stopped the other scripts and domains, running only save/restore on a
single domain, and see the crash rather quickly (within 10 iterations).

> But I've slept on this and I had an idea about libvirt's rescheduling
> timeouts. 

I'm not so thrilled with the timeout handling code in the libvirt libxl
driver.  The driver maintains a list of active timeouts because IIRC,
there were cases when the driver received timeout deregistrations when
calling libxl_ctx_free, at which point some of the associated structures
were freed.  The idea was to call libxl_osevent_occurred_timeout on any
active timeouts before freeing libxlDomainObjPrivate and its contents.

Regards,
Jim


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