Re: [patch] cpufreq: mark cpufreq_tsc() as core_initcall_sync

From: Oleg Nesterov
Date: Mon Nov 27 2006 - 11:57:30 EST


On 11/27, Oleg Nesterov wrote:
>
> so synchronize_xxx() should be
>
> void synchronize_xxx(struct xxx_struct *sp)
> {
> int idx;
>
> smp_mb();
> mutex_lock(&sp->mutex);
>
> idx = sp->completed & 0x1;
> if (atomic_read(sp->ctr + idx) == 1)
> goto out;
>
> atomic_inc(sp->ctr + (idx ^ 0x1));
> sp->completed++;
>
> atomic_dec(sp->ctr + idx);
> wait_event(sp->wq, !atomic_read(sp->ctr + idx));
> out:
> mutex_unlock(&sp->mutex);
> }
>
> Yes, Alan was right, spinlock_t makes the code simpler.

Damn, it needs another mb() at the end,

void synchronize_xxx(struct xxx_struct *sp)
{
int idx;

smp_mb();
mutex_lock(&sp->mutex);

idx = sp->completed & 0x1;
if (atomic_read(sp->ctr + idx) == 1)
goto out;

atomic_inc(sp->ctr + (idx ^ 0x1));
sp->completed++;

atomic_dec(sp->ctr + idx);
wait_event(sp->wq, !atomic_read(sp->ctr + idx));
out:
mutex_unlock(&sp->mutex);
smp_mb();
}

Oleg.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/