svn commit: r300154 - head/sys/net

[Bjoern A. Zeeb]

> On 18 May 2016, at 17:32 , 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.)


Question because I didn’t follow the details, but how was this solved for the COUNTERS framework?


/bz