Matt Turner wrote:
Hi,
Going on Richard's advice, I've tried to write an alpha futex
implementation based on the powerpc futex.h.
I've gotten this far.. :\
#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
__asm__ __volatile( \
__ASM_MB \
"1: ldl_l %0,0(%3)\n" \
insn \
"2: stl_c %1,0(%3)\n" \
" beq %1,4f\n" \
" mov $31,%1\n" \
"3: .subsection 2\n" \
"4: br 1b\n" \
" .previous\n" \
".section __ex_table,\"a\"\n" \
" .long 1b-.\n" \
" lda %0,3b-1b(%2)\n" \
" .long 2b-.\n" \
" lda %0,3b-2b(%2)\n" \
" .previous\n" \
: "=&r" (oldval), "=&r"(ret) \
: "r" (uaddr), "r"(oparg) \
: "memory")
switch (op) {
case FUTEX_OP_SET:
__futex_atomic_op("mov %0,%1", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_ADD:
__futex_atomic_op("addl %0,%4,%1\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_OR:
__futex_atomic_op("or %0,%4,%1\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_ANDN:
__futex_atomic_op("andnot %0,%4,%1\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_XOR:
__futex_atomic_op("xor %0,%4,%1\n", ret, oldval, uaddr, oparg);
break;
default:
ret = -ENOSYS;
}
Also, there's a bug in the powerpc implementation. It appears that
oparg is clobbered, and if stwcx fails the operation will be repeated
with incorrect inputs.
r~
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