Re: [PATCH v10 1/2] ring-buffer: Introducing ring-buffer mapping functions

[Vincent Donnefort <vdonnefort@google.com>]

[...]

> > > +	 */
> > > +	smp_wmb();
> > > +	WRITE_ONCE(cpu_buffer->mapped, 1);
> > > +
> > > +	/* Init meta_page values unless the writer did it already */
> > > +	cmpxchg(&cpu_buffer->meta_page->entries, 0,
> > > +		local_read(&cpu_buffer->entries));
> > > +	cmpxchg(&cpu_buffer->meta_page->overrun, 0,
> > > +		local_read(&cpu_buffer->overrun));
> > > +	cmpxchg(&cpu_buffer->meta_page->subbufs_touched, 0,
> > > +		local_read(&cpu_buffer->pages_touched));
> > > +	cmpxchg(&cpu_buffer->meta_page->subbufs_lost, 0,
> > > +		local_read(&cpu_buffer->pages_lost));
> > 
> > Instead of using these cmpxchg, can we move this initialization before
> > smp_wmb()? Thus we can avoid conflict with rb_update_meta_page()
> 
> Good point, Not sure why I made this more complicated than it should be.

Ha, I know, that was before v6, where the writer was updating all of that. From
v6 the update has been moved to the irq_rb_work.

> 
> > 
> > Thank you,
> >
> 
> [...]