svn commit: r300154 - head/sys/net

[Adrian Chadd]

On 18 May 2016 at 10:32, Ian Lepore <ian at freebsd.org> wrote:
> 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.)

Please, please do this. Don't do a list of platforms, do a list of
features. Pretty please.



-adrian