On Tue, May 12, 2015 at 08:32:32PM +0800, Lai Jiangshan wrote:
> If the cpuamsk is changed, it is possible that only a part of the per-node
cpumask
> pwq is affected. This can happen when the user changes the cpumask of
> a workqueue or the low level cpumask.
>
> So we try to reuse the current per-node pwq when its attrs unchanged.
are unchanged.
> @@ -3592,9 +3593,14 @@ apply_wqattrs_prepare(struct workqueue_struct *wq,
>
> for_each_node(node) {
> if (wq_calc_node_cpumask(new_attrs, node, -1,
> tmp_attrs->cpumask)) {
> - ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
> - if (!ctx->pwq_tbl[node])
> + pwq = unbound_pwq_by_node(wq, node);
> + if (pwq && wqattrs_equal(tmp_attrs, pwq->pool->attrs))
> + pwq = get_pwq_unlocked(pwq);
Ah, okay, the function gets used here again. BTW, why does this
function return anything? Can this function ever return something
which isn't the pwq it was called with?
> + else
> + pwq = alloc_unbound_pwq(wq, tmp_attrs);
> + if (!pwq)
> goto out_free;
If get_pwq_unlocked() can't fail, why are we testing for NULL pwq
here? This code is kinda misleading.
> + ctx->pwq_tbl[node] = pwq;
> } else {
> ctx->dfl_pwq->refcnt++;
> ctx->pwq_tbl[node] = ctx->dfl_pwq;
> @@ -3739,7 +3745,6 @@ static void wq_update_unbound_numa(struct
> workqueue_struct *wq, int cpu,
> cpumask = target_attrs->cpumask;
>
> copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
> - pwq = unbound_pwq_by_node(wq, node);
>
> /*
> * Let's determine what needs to be done. If the target cpumask is
> @@ -3748,6 +3753,7 @@ static void wq_update_unbound_numa(struct
> workqueue_struct *wq, int cpu,
> * equals the default pwq's, the default pwq should be used.
> */
> if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off,
> cpumask)) {
> + pwq = unbound_pwq_by_node(wq, node);
It'd be nice to note this change in the patch description.
Thanks.
--
tejun
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