diff options
Diffstat (limited to 'tools/arch/sparc/include/asm/barrier_64.h')
| -rw-r--r-- | tools/arch/sparc/include/asm/barrier_64.h | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/tools/arch/sparc/include/asm/barrier_64.h b/tools/arch/sparc/include/asm/barrier_64.h new file mode 100644 index 000000000000..9a7d7322c3f7 --- /dev/null +++ b/tools/arch/sparc/include/asm/barrier_64.h @@ -0,0 +1,42 @@ +#ifndef __TOOLS_LINUX_SPARC64_BARRIER_H +#define __TOOLS_LINUX_SPARC64_BARRIER_H + +/* Copied from the kernel sources to tools/: + * + * These are here in an effort to more fully work around Spitfire Errata + * #51. Essentially, if a memory barrier occurs soon after a mispredicted + * branch, the chip can stop executing instructions until a trap occurs. + * Therefore, if interrupts are disabled, the chip can hang forever. + * + * It used to be believed that the memory barrier had to be right in the + * delay slot, but a case has been traced recently wherein the memory barrier + * was one instruction after the branch delay slot and the chip still hung. + * The offending sequence was the following in sym_wakeup_done() of the + * sym53c8xx_2 driver: + * + * call sym_ccb_from_dsa, 0 + * movge %icc, 0, %l0 + * brz,pn %o0, .LL1303 + * mov %o0, %l2 + * membar #LoadLoad + * + * The branch has to be mispredicted for the bug to occur. Therefore, we put + * the memory barrier explicitly into a "branch always, predicted taken" + * delay slot to avoid the problem case. + */ +#define membar_safe(type) \ +do { __asm__ __volatile__("ba,pt %%xcc, 1f\n\t" \ + " membar " type "\n" \ + "1:\n" \ + : : : "memory"); \ +} while (0) + +/* The kernel always executes in TSO memory model these days, + * and furthermore most sparc64 chips implement more stringent + * memory ordering than required by the specifications. + */ +#define mb() membar_safe("#StoreLoad") +#define rmb() __asm__ __volatile__("":::"memory") +#define wmb() __asm__ __volatile__("":::"memory") + +#endif /* !(__TOOLS_LINUX_SPARC64_BARRIER_H) */ |