| Message ID | 1395330365-9901-3-git-send-email-ian.campbell@citrix.com |
|---|---|
| State | Superseded |
| Headers | show |
Hi Ian, On 03/20/2014 03:45 PM, Ian Campbell wrote: > Unrelated reads/writes should not pass the xchg. > > Provide cmpxchg_local for parity with arm64, although it appears to be unused. > It also helps make the reason for the separation of __cmpxchg_mb more > apparent. > > With this our cmpxchg is in sync with Linux v3.14-rc7. > > Signed-off-by: Ian Campbell <ian.campbell@citrix.com> > --- > We got our cmpxchg implementation from Linux which AFAICS has always had these > additional barriers. I don't recall us having decided that Xen barriers should > not have this property as well, and if we did we were remiss in not adding a > comment etc... If my memory is faulty then I am happy to replace thispatch > with one which adds a comment instead. I think the barrier is good for Xen. We may have some place where both of this macro are used as a "barrier". Acked-by: Julien Grall <julien.grall@linaro.org> Regards,
diff --git a/xen/include/asm-arm/arm32/system.h b/xen/include/asm-arm/arm32/system.h index 9f233fe..dfaa3b6 100644 --- a/xen/include/asm-arm/arm32/system.h +++ b/xen/include/asm-arm/arm32/system.h @@ -113,9 +113,29 @@ static always_inline unsigned long __cmpxchg( return oldval; } -#define cmpxchg(ptr,o,n) \ - ((__typeof__(*(ptr)))__cmpxchg((ptr),(unsigned long)(o), \ - (unsigned long)(n),sizeof(*(ptr)))) +static inline unsigned long __cmpxchg_mb(volatile void *ptr, unsigned long old, + unsigned long new, int size) +{ + unsigned long ret; + + smp_mb(); + ret = __cmpxchg(ptr, old, new, size); + smp_mb(); + + return ret; +} + +#define cmpxchg(ptr,o,n) \ + ((__typeof__(*(ptr)))__cmpxchg_mb((ptr), \ + (unsigned long)(o), \ + (unsigned long)(n), \ + sizeof(*(ptr)))) + +#define cmpxchg_local(ptr,o,n) \ + ((__typeof__(*(ptr)))__cmpxchg((ptr), \ + (unsigned long)(o), \ + (unsigned long)(n), \ + sizeof(*(ptr)))) #define local_irq_disable() asm volatile ( "cpsid i @ local_irq_disable\n" : : : "cc" ) #define local_irq_enable() asm volatile ( "cpsie i @ local_irq_enable\n" : : : "cc" )
Unrelated reads/writes should not pass the xchg. Provide cmpxchg_local for parity with arm64, although it appears to be unused. It also helps make the reason for the separation of __cmpxchg_mb more apparent. With this our cmpxchg is in sync with Linux v3.14-rc7. Signed-off-by: Ian Campbell <ian.campbell@citrix.com> --- We got our cmpxchg implementation from Linux which AFAICS has always had these additional barriers. I don't recall us having decided that Xen barriers should not have this property as well, and if we did we were remiss in not adding a comment etc... If my memory is faulty then I am happy to replace thispatch with one which adds a comment instead. --- xen/include/asm-arm/arm32/system.h | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-)