[Barrelfish-users] Assertion fired when calling "nameserver_register" function

Kornilios Kourtis kornilios.kourtis at inf.ethz.ch
Fri Jan 10 17:35:08 CET 2014


Hi Mark,

On Thu, Jan 09, 2014 at 05:48:07PM +0000, M Brown wrote:
> Kornilios,
> 
>  I believe that I have found a bug in the nameserver. The
> problem appears to be in the use of the nameserver functions in
> multiple threads running on a single core. In this case the
> nameserver functions are non-reentrant. To illustrate this I
> took your message example (xmpl-msg) and wrapped both the client
> and server functions in separate threads and ran the application
> on a single core. The same assertion fired as illustrated below:
> 
> The nameservice blocking lookup is invoked by the client
> application near the beginning to get the iref. The server then
> tries to register the iref in the nameserver and gets the
> assertion.
> 
> In general for the nameserver to be useful, it needs to be
> accessible by any number of threads running on any number of
> cores in a concurrent manner.

It seems that you are using multiple threads (spanned domains)
to access the messaging infrastructure of Barrelfish. As far as
I know, spanned domains were implemented as a quick way to
enable running shared-memory applications, and a significant
part of the barrelfish infrastructure (e.g., messages) will not
work correctly with them. To the best of my knowledge, the only
thing that works reliably on a spanned domain is thread
synchronization primitives.

I'm afraid this is not an easy problem to fix. My suggestion
would be to avoid spanned domains altogether. If this is not
possible the only quick solution I can think of is protecting
libbarrelfish invocations with a lock.

cheers,
Kornilios.


>  
> 
> Thanks,
> 
>  
> 
> Mark Brown
> 
> Huawei Technologies Inc.
> 
> 5340 Legacy Dr., Suite 175
> 
> Plano, TX 75024
> 
> Tel: 469-277-5700 x5870
> 
> Email: m.brown at huawei.com
> 
>  
> 
> -----Original Message-----
> From: Kornilios Kourtis [mailto:kornilios.kourtis at inf.ethz.ch]
> Sent: Thursday, December 19, 2013 6:33 AM
> To: M Brown
> Cc: barrelfish-users at lists.inf.ethz.ch
> Subject: Re: [Barrelfish-users] Assertion fired when calling
> "nameserver_register" function
> 
>  
> 
> Dear Mark,
> 
>  
> 
> On Mon, Dec 16, 2013 at 05:38:37PM +0000, M Brown wrote:
> 
> > Guys,
> 
> >
> 
> >    I’m getting the following assertion fired when calling the
> 
> >    nameserver_register function from within an export callback
> 
> >    function:
> 
> >
> 
> > [cid]
> 
> >
> 
> > The example message test works fine. The structure of the code I have
> 
> > is as follows:
> 
> >
> 
> > main {
> 
> >                 thread_create(myTask, NULL);
> 
> >                 .
> 
> >                 .
> 
> >                 .
> 
> > }
> 
> >
> 
> > int myTask(void* arg) {
> 
> >                 .
> 
> >                 .
> 
> >                 .
> 
> >                 <iface>_export(NULL,
> 
> >                                export_cb, connect_cb,
> 
> >                                get_default_waitset(),
> 
> >                                IDC_EXPORT_FLAGS_DEFAULT);
> 
> >
> 
> > }
> 
> >
> 
> > void export_cb(void *st, errval_t err, iref_t iref) {
> 
> >                 .
> 
> >                 .
> 
> >                 .
> 
> >                 // The assertion fires within this invocation
> 
> >                 nameserver_register(“iface”, iref); }
> 
> >
> 
> > Is there something I’m doing wrong here?
> 
>  
> 
> [I'm guessing you mean nameservice_register() above]
> 
>  
> 
> Judging from the failed assertion (!_rpc->rpc_in_progress), I'm guessing that
> it might have something to do with using multiple threads. What are the other
> threads doing? Can you reproduce the problem when using a single thread?
> 
>  
> 
> cheers,
> 
> Kornilios.
> 
>  
> 
> --
> 
> Kornilios Kourtis
> 
>  
> 
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> 
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> 
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> 
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> 



-- 
Kornilios Kourtis



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