Re: [CFT][RFC] HT scheduler

[Nick Piggin]

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.


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