[uclibc-ng-devel] [PATCH 1/3] NPTL/ARC: implement __arch_exchange_32_acq using native EX

ARC EX instruction maps directly to this primitive, thus helps elide the llock/scond based retry loop where possible. Signed-off-by: Vineet Gupta <vgupta(a)synopsys.com> --- libc/sysdeps/linux/arc/bits/atomic.h | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/libc/sysdeps/linux/arc/bits/atomic.h b/libc/sysdeps/linux/arc/bits/atomic.h index 1fdc83f70f6b..48f37879c5c4 100644 --- a/libc/sysdeps/linux/arc/bits/atomic.h +++ b/libc/sysdeps/linux/arc/bits/atomic.h @@ -58,3 +58,27 @@ void __arc_link_error (void); #define __arch_compare_and_exchange_val_64_acq(mem, newval, oldval) \ ({ __arc_link_error (); oldval; }) + +/* Store NEWVALUE in *MEM and return the old value. + Atomic EX is present in all configurations + */ + +#define __arch_exchange_32_acq(mem, newval) \ + ({ \ + __typeof__(*(mem)) val = newval; \ + \ + __asm__ __volatile__( \ + "ex %0, [%1]" \ + : "+r" (val) \ + : "r" (mem) \ + : "memory" ); \ + \ + val; \ + }) + +#define atomic_exchange_acq(mem, newval) \ + ({ \ + if (sizeof(*(mem)) != 4) \ + abort(); \ + __arch_exchange_32_acq(mem, newval); \ + }) -- 2.7.4