svn commit: r300154 - head/sys/net

[Ian Lepore]

On Wed, 2016-05-18 at 10:14 -0700, Nathan Whitehorn wrote:
> 
> On 05/18/16 08:50, Justin Hibbits wrote:
> > On Wed, 18 May 2016 15:45:12 +0000 (UTC)
> > Scott Long <scottl at FreeBSD.org> wrote:
> > 
> > > Author: scottl
> > > Date: Wed May 18 15:45:12 2016
> > > New Revision: 300154
> > > URL: https://svnweb.freebsd.org/changeset/base/300154
> > > 
> > > Log:
> > >    Activate the NO_64BIT_ATOMICS code for mips and powerpc
> > > 
> > > Modified:
> > >    head/sys/net/mp_ring.c
> > > 
> > > Modified: head/sys/net/mp_ring.c
> > > =================================================================
> > > =============
> > > --- head/sys/net/mp_ring.c	Wed May 18 15:44:45 2016
> > > (r300153) +++ head/sys/net/mp_ring.c	Wed May 18 15:45:12
> > > 2016	(r300154) @@ -37,15 +37,17 @@ __FBSDID("$FreeBSD$");
> > >   #include <sys/malloc.h>
> > >   #include <machine/cpu.h>
> > >   
> > > -
> > > -
> > > -#include <net/mp_ring.h>
> > > +#if defined(__powerpc__) || defined(__mips__)
> > > +#define NO_64BIT_ATOMICS
> > > +#endif
> > >   
> > >   #if defined(__i386__)
> > >   #define atomic_cmpset_acq_64 atomic_cmpset_64
> > >   #define atomic_cmpset_rel_64 atomic_cmpset_64
> > >   #endif
> > >   
> > > +#include <net/mp_ring.h>
> > > +
> > >   union ring_state {
> > >   	struct {
> > >   		uint16_t pidx_head;
> > > 
> > powerpc64 defines both __powerpc__ and __powerpc64__, so you're
> > killing
> > atomics on powerpc64 with this.
> > 
> > - Justin
> > 
> 
> Don't all of our 64-bit platforms have 64-bit atomics? So you could
> just 
> #if defined(__LP64__) || defined(__i386__) || 
> defined(__whatever_the_thing_is_for_mips_n32__)
> -Nathan
> 

It may be more complicated than that, though.  armv6 can do 64-bit
atomics even tho it's 32-bit.  armv4, also 32-bit, can do 64-bit
atomics in the kernel but not in userland.

Maybe machine/atomic.h needs a #define that says whether 64-bit ops are
available in the current compilation unit.  (And likewise for other bit
sizes if we have arches that have other limitations.)

-- Ian