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    SubjectRe: [CFT][RFC] HT scheduler


    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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