From
http://code.google.com/p/google-perftools/source/browse/trunk/src/base/atomicops-internals-x86.h
bool has_amd_lock_mb_bug; // Processor has AMD memory-barrier bug; do lfence
// after acquire compare-and-swap.
...
inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
Atomic32 prev;
__asm__ __volatile__("lock; cmpxchgl %1,%2"
: "=a" (prev)
: "q" (new_value), "m" (*ptr), "0" (old_value)
: "memory");
return prev;
}
inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
Atomic32 x = NoBarrier_CompareAndSwap(ptr, old_value, new_value);
if (AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug) {
__asm__ __volatile__("lfence" : : : "memory");
}
return x;
}
inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
}
This bug can also affect lock+xadd combinations.
--
Summary: AMD Opteron E needs workaround for lock erratum
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Keywords: openmp
Severity: normal
Priority: P3
Component: middle-end
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: bonzini at gnu dot org
GCC target triplet: i386-*-*, x86_64-*-*
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39677
