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.
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