diff options
| author | David S. Miller <davem@davemloft.net> | 2012-10-28 13:04:47 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-10-28 13:04:47 -0700 |
| commit | 187818cd6a5ab6343eac47e52da2f3e40c544b98 (patch) | |
| tree | 09b55dad78359ae7e047f3eb533844adaa4094c6 /arch/sparc/include/asm/processor_64.h | |
| parent | e9b9eb59ffcdee09ec96b040f85c919618f4043e (diff) | |
sparc64: Improvde documentation and readability of atomic backoff code.
Document what's going on in asm/backoff.h with a large and descriptive
comment. Refer to it above the cpu_relax() definition in
asm/processor_64.h
Rename the pause patching section to have "3insn" in it's name like
the other patching sections do.
Based upon feedback from Sam Ravnborg.
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/sparc/include/asm/processor_64.h')
| -rw-r--r-- | arch/sparc/include/asm/processor_64.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/sparc/include/asm/processor_64.h b/arch/sparc/include/asm/processor_64.h index 9cdf52eec48..721e25f0e2e 100644 --- a/arch/sparc/include/asm/processor_64.h +++ b/arch/sparc/include/asm/processor_64.h @@ -196,11 +196,16 @@ extern unsigned long get_wchan(struct task_struct *task); #define KSTK_EIP(tsk) (task_pt_regs(tsk)->tpc) #define KSTK_ESP(tsk) (task_pt_regs(tsk)->u_regs[UREG_FP]) +/* Please see the commentary in asm/backoff.h for a description of + * what these instructions are doing and how they have been choosen. + * To make a long story short, we are trying to yield the current cpu + * strand during busy loops. + */ #define cpu_relax() asm volatile("\n99:\n\t" \ "rd %%ccr, %%g0\n\t" \ "rd %%ccr, %%g0\n\t" \ "rd %%ccr, %%g0\n\t" \ - ".section .pause_patch,\"ax\"\n\t"\ + ".section .pause_3insn_patch,\"ax\"\n\t"\ ".word 99b\n\t" \ "wr %%g0, 128, %%asr27\n\t" \ "nop\n\t" \ |