Re: [PATCH V6 2/2] genirq/affinity: Spread vectors on node according to nr_cpu ratio

[Thomas Gleixner]

On Mon, 19 Aug 2019, Ming Lei wrote:
> On Mon, Aug 19, 2019 at 03:13:58PM +0200, Thomas Gleixner wrote:
> > On Mon, 19 Aug 2019, Ming Lei wrote:
> > 
> > > Cc: Jon Derrick <jonathan.derrick@xxxxxxxxx>
> > > Cc: Jens Axboe <axboe@xxxxxxxxx>
> > > Reported-by: Jon Derrick <jonathan.derrick@xxxxxxxxx>
> > > Reviewed-by: Jon Derrick <jonathan.derrick@xxxxxxxxx>
> > > Reviewed-by: Keith Busch <kbusch@xxxxxxxxxx>
> > 
> > This version is sufficiently different from the previous one, so I do not
> > consider the reviewed-by tags still being valid and meaningful. Don't
> > include them unless you just do cosmetic changes.
> 
> Fine.
> 
> However, the V6 only change isn't big, just for addressing the un-initialized
> warning, and the change is only done on function of irq_build_affinity_masks().

They are not trivial either:

 affinity.c |   28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

--- a/kernel/irq/affinity.c
+++ b/kernel/irq/affinity.c
@@ -339,7 +339,7 @@ static int irq_build_affinity_masks(unsi
 				    unsigned int firstvec,
 				    struct irq_affinity_desc *masks)
 {
-	unsigned int curvec = startvec, nr_present, nr_others;
+	unsigned int curvec = startvec, nr_present = 0, nr_others = 0;
 	cpumask_var_t *node_to_cpumask;
 	cpumask_var_t nmsk, npresmsk;
 	int ret = -ENOMEM;
@@ -354,19 +354,17 @@ static int irq_build_affinity_masks(unsi
 	if (!node_to_cpumask)
 		goto fail_npresmsk;
 
-	ret = 0;
 	/* Stabilize the cpumasks */
 	get_online_cpus();
 	build_node_to_cpumask(node_to_cpumask);
 
 	/* Spread on present CPUs starting from affd->pre_vectors */
-	nr_present = __irq_build_affinity_masks(curvec, numvecs,
-						firstvec, node_to_cpumask,
-						cpu_present_mask, nmsk, masks);
-	if (nr_present < 0) {
-		ret = nr_present;
+	ret = __irq_build_affinity_masks(curvec, numvecs, firstvec,
+					 node_to_cpumask, cpu_present_mask,
+					 nmsk, masks);
+	if (ret < 0)
 		goto fail_build_affinity;
-	}
+	nr_present = ret;
 
 	/*
 	 * Spread on non present CPUs starting from the next vector to be
@@ -379,16 +377,16 @@ static int irq_build_affinity_masks(unsi
 	else
 		curvec = firstvec + nr_present;
 	cpumask_andnot(npresmsk, cpu_possible_mask, cpu_present_mask);
-	nr_others = __irq_build_affinity_masks(curvec, numvecs,
-					       firstvec, node_to_cpumask,
-					       npresmsk, nmsk, masks);
-	if (nr_others < 0)
-		ret = nr_others;
+	ret = __irq_build_affinity_masks(curvec, numvecs, firstvec,
+					 node_to_cpumask, npresmsk, nmsk,
+					 masks);
+	if (ret >= 0)
+		nr_others = ret;
 
  fail_build_affinity:
 	put_online_cpus();
 
-	if (min(nr_present, nr_others) >= 0)
+	if (ret >= 0)
 		WARN_ON(nr_present + nr_others < numvecs);
 
 	free_node_to_cpumask(node_to_cpumask);
@@ -398,7 +396,7 @@ static int irq_build_affinity_masks(unsi
 
  fail_nmsk:
 	free_cpumask_var(nmsk);
-	return ret;
+	return ret < 0 ? ret : 0;
 }
 
 static void default_calc_sets(struct irq_affinity *affd, unsigned int affvecs)