ref: cdcc2bf6944fa9f0765a5c3c990eb6b0b12b605d
dir: /posix-power/tas.c/
#include "u.h" #include "libc.h" /* * first argument (l) is in r3 at entry. * r3 contains return value upon return. */ int tas(long *x) { int v; /* * this __asm__ works with gcc 2.95.2 (mac os x 10.1). * this assembly language destroys r0 (0), some other register (v), * r4 (x) and r5 (temp). */ __asm__("\n sync\n" " li r0,0\n" " mr r4,%1 /* &l->val */\n" " lis r5,0xdead /* assemble constant 0xdeaddead */\n" " ori r5,r5,0xdead /* \" */\n" "tas1:\n" " dcbf r4,r0 /* cache flush; \"fix for 603x bug\" */\n" " lwarx %0,r4,r0 /* v = l->val with reservation */\n" " cmp cr0,0,%0,r0 /* v == 0 */\n" " bne tas0\n" " stwcx. r5,r4,r0 /* if (l->val same) l->val = 0xdeaddead */\n" " bne tas1\n" "tas0:\n" " sync\n" " isync\n" : "=r" (v) : "r" (x) : "cc", "memory", "r0", "r4", "r5" ); switch(v) { case 0: return 0; case 0xdeaddead: return 1; default: print("tas: corrupted 0x%lux\n", v); } return 0; }