Re: [Xen-devel] [PATCH RFC v2 09/13] libxl: introduce lock in libxl_ctx

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2011-11-02 at 12:38 -0400, Ian Jackson wrote:
> Ian Campbell writes ("Re: [Xen-devel] [PATCH RFC v2 09/13] libxl: introduce 
> lock in libxl_ctx"):
> > On Fri, 2011-10-28 at 19:37 +0100, Ian Jackson wrote:
> > > +    const pthread_mutex_t mutex_value = 
> > > PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
> ...
> > > +    memcpy(&ctx->lock, &mutex_value, sizeof(ctx->lock));
> > 
> > Is this subtly different to
> >        ctx->lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
> > in some way I'm missing?
> 
> Yes.  PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP is formally valid only as
> an initialiser, not necessarily as an expression.  I'm not sure that
> relevant GCC extensions mean the two are always equivalent.

OK, thanks.

I just had a read of pthread_mutex(3) and I'm surprised how many hoops
one has to jump through to use pthread_mutex_init(). Well, I say
surprised...

Ian.


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