Re: [CFT][RFC] HT scheduler

Nick Piggin
2003-12-11T16:37:29Z

William Lee Irwin III wrote:

>William Lee Irwin III wrote:
>
>>>There is a spinloop in __up_read(), which is probably it.
>>>
>
>On Fri, Dec 12, 2003 at 02:51:32AM +1100, Nick Piggin wrote:
>
>>Oh I see - in rwsem_wake?
>>
>
>Even before that:
>
>static inline void __up_read(struct rw_semaphore *sem)
>{
> __s32 tmp = -RWSEM_ACTIVE_READ_BIAS;
> __asm__ __volatile__(
> "# beginning __up_read\n\t"
>LOCK_PREFIX " xadd %%edx,(%%eax)\n\t" /* subtracts 1, returns the old value */
> " js 2f\n\t" /* jump if the lock is being waited upon */
> "1:\n\t"
> LOCK_SECTION_START("")
> "2:\n\t"
> " decw %%dx\n\t" /* do nothing if still outstanding active readers
> */
> " jnz 1b\n\t"
> " pushl %%ecx\n\t"
> " call rwsem_wake\n\t"
> " popl %%ecx\n\t"
> " jmp 1b\n"
> LOCK_SECTION_END
>

I think there shouldn't be a loop - remember the lock section.