Le jeudi 28 avril 2011 Ã 11:17 -0500, Christoph Lameter a Ãcrit :
> On Thu, 28 Apr 2011, Eric Dumazet wrote:
>
> > > If _sum() notices seqcount was changed too much, restart the loop.
>
> This does not address the issue of cpus adding batch -1 while the
> loop is going on.
Yes, it does, I left the needed changes to write side as an exercice ;)
For example, based on current linux-2.6 code
void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
{
s64 count;
preempt_disable();
count = __this_cpu_read(*fbc->counters) + amount;
if (count >= batch || count <= -batch) {
spin_lock(&fbc->lock);
fbc->seqcount++;
fbc->count += count;
__this_cpu_write(*fbc->counters, 0);
spin_unlock(&fbc->lock);
} else {
__this_cpu_write(*fbc->counters, count);
}
preempt_enable();
}
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