[Development] QBasicMutex::lockInternal() race condition?

[Tony Van Eerd]

But we already did an acquire earlier when we got the d_ptr the first time.  All our instructions on id and waiters happens after that.

If we are worried about ABA on the d_ptr, hmmm, I'd need to think about that.

 

> -----Original Message-----
> From: development-bounces+tvaneerd=rim.com at qt-project.org
> [mailto:development-bounces+tvaneerd=rim.com at qt-project.org] On Behalf
> Of Thiago Macieira
> Sent: Thursday, September 20, 2012 12:14 PM
> To: development at qt-project.org
> Subject: Re: [Development] QBasicMutex::lockInternal() race condition?
> 
> On quinta-feira, 20 de setembro de 2012 15.50.12, Tony Van Eerd wrote:
> > > We check for that case shortly after:
> > >
> > >
> > > 361     if (d != d_ptr.loadAcquire()) {
> > > 362        //Either the mutex is already unlocked, or relocked with
> > > another mutex
> > > 363        d->deref();
> > > 364        continue;
> > > 365     }
> > >
> > >
> >
> > Or course.  Very next lines!  "shortly after" is a being nice to me.
> Sorry.
> >
> > I wonder if the Acquire couldn't be Relaxed...
> 
> Acquire is correct, since we'll use some of the fields that requires
> memory
> ordering, like the id or waiters fields.
> 
> --
> Thiago Macieira - thiago.macieira (AT) intel.com
>   Software Architect - Intel Open Source Technology Center
>      Intel Sweden AB - Registration Number: 556189-6027
>      Knarrarnäsgatan 15, 164 40 Kista, Stockholm, Sweden

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