In general it's preferable to avoid placing cpumasks on the stack, as
for large values of NR_CPUS these can consume significant amounts of
stack space and make stack overflows more likely.

Use cpumask_first_and_and() to avoid the need for a temporary cpumask on
the stack.

Signed-off-by: Dawei Li <dawei.li@shingroup.cn>
---
 drivers/irqchip/irq-loongson-eiointc.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/irqchip/irq-loongson-eiointc.c b/drivers/irqchip/irq-loongson-eiointc.c
index 4f5e6d21d77d..c7ddebf312ad 100644
--- a/drivers/irqchip/irq-loongson-eiointc.c
+++ b/drivers/irqchip/irq-loongson-eiointc.c
@@ -93,19 +93,15 @@ static int eiointc_set_irq_affinity(struct irq_data *d, const struct cpumask *af
 	unsigned int cpu;
 	unsigned long flags;
 	uint32_t vector, regaddr;
-	struct cpumask intersect_affinity;
 	struct eiointc_priv *priv = d->domain->host_data;
 
 	raw_spin_lock_irqsave(&affinity_lock, flags);
 
-	cpumask_and(&intersect_affinity, affinity, cpu_online_mask);
-	cpumask_and(&intersect_affinity, &intersect_affinity, &priv->cpuspan_map);
-
-	if (cpumask_empty(&intersect_affinity)) {
+	cpu = cpumask_first_and_and(&priv->cpuspan_map, affinity, cpu_online_mask);
+	if (cpu >= nr_cpu_ids) {
 		raw_spin_unlock_irqrestore(&affinity_lock, flags);
 		return -EINVAL;
 	}
-	cpu = cpumask_first(&intersect_affinity);
 
 	vector = d->hwirq;
 	regaddr = EIOINTC_REG_ENABLE + ((vector >> 5) << 2);
-- 
2.27.0

On Tue, Apr 16, 2024 at 04:54:51PM +0800, Dawei Li wrote:
> In general it's preferable to avoid placing cpumasks on the stack, as
> for large values of NR_CPUS these can consume significant amounts of
> stack space and make stack overflows more likely.
> 
> Use cpumask_first_and_and() to avoid the need for a temporary cpumask on
> the stack.
> 
> Signed-off-by: Dawei Li <dawei.li@shingroup.cn>
> ---
>  drivers/irqchip/irq-loongson-eiointc.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-loongson-eiointc.c b/drivers/irqchip/irq-loongson-eiointc.c
> index 4f5e6d21d77d..c7ddebf312ad 100644
> --- a/drivers/irqchip/irq-loongson-eiointc.c
> +++ b/drivers/irqchip/irq-loongson-eiointc.c
> @@ -93,19 +93,15 @@ static int eiointc_set_irq_affinity(struct irq_data *d, const struct cpumask *af
>  	unsigned int cpu;
>  	unsigned long flags;
>  	uint32_t vector, regaddr;
> -	struct cpumask intersect_affinity;
>  	struct eiointc_priv *priv = d->domain->host_data;
>  
>  	raw_spin_lock_irqsave(&affinity_lock, flags);
>  
> -	cpumask_and(&intersect_affinity, affinity, cpu_online_mask);
> -	cpumask_and(&intersect_affinity, &intersect_affinity, &priv->cpuspan_map);
> -
> -	if (cpumask_empty(&intersect_affinity)) {

This was unneeded because cpumask_and() returns true if there are set
bits.

For the series:

Reviewed-by: Yury Norov <yury.norov@gmail.com>

> +	cpu = cpumask_first_and_and(&priv->cpuspan_map, affinity, cpu_online_mask);
> +	if (cpu >= nr_cpu_ids) {
>  		raw_spin_unlock_irqrestore(&affinity_lock, flags);
>  		return -EINVAL;
>  	}
> -	cpu = cpumask_first(&intersect_affinity);
>  
>  	vector = d->hwirq;
>  	regaddr = EIOINTC_REG_ENABLE + ((vector >> 5) << 2);
> -- 
> 2.27.0

The following commit has been merged into the irq/core branch of tip:

Commit-ID:     2bc32db5a262cc34753cb4208b2d3043d1cd81ae
Gitweb:        https://git.kernel.org/tip/2bc32db5a262cc34753cb4208b2d3043d1cd81ae
Author:        Dawei Li <dawei.li@shingroup.cn>
AuthorDate:    Tue, 16 Apr 2024 16:54:51 +08:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Wed, 24 Apr 2024 21:23:49 +02:00

irqchip/loongson-eiointc: Avoid explicit cpumask allocation on stack

In general it's preferable to avoid placing cpumasks on the stack, as
for large values of NR_CPUS these can consume significant amounts of
stack space and make stack overflows more likely.

Use cpumask_first_and_and() to avoid the need for a temporary cpumask on
the stack.

Signed-off-by: Dawei Li <dawei.li@shingroup.cn>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Link: https://lore.kernel.org/r/20240416085454.3547175-5-dawei.li@shingroup.cn

---
 drivers/irqchip/irq-loongson-eiointc.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/irqchip/irq-loongson-eiointc.c b/drivers/irqchip/irq-loongson-eiointc.c
index 4f5e6d2..c7ddebf 100644
--- a/drivers/irqchip/irq-loongson-eiointc.c
+++ b/drivers/irqchip/irq-loongson-eiointc.c
@@ -93,19 +93,15 @@ static int eiointc_set_irq_affinity(struct irq_data *d, const struct cpumask *af
 	unsigned int cpu;
 	unsigned long flags;
 	uint32_t vector, regaddr;
-	struct cpumask intersect_affinity;
 	struct eiointc_priv *priv = d->domain->host_data;
 
 	raw_spin_lock_irqsave(&affinity_lock, flags);
 
-	cpumask_and(&intersect_affinity, affinity, cpu_online_mask);
-	cpumask_and(&intersect_affinity, &intersect_affinity, &priv->cpuspan_map);
-
-	if (cpumask_empty(&intersect_affinity)) {
+	cpu = cpumask_first_and_and(&priv->cpuspan_map, affinity, cpu_online_mask);
+	if (cpu >= nr_cpu_ids) {
 		raw_spin_unlock_irqrestore(&affinity_lock, flags);
 		return -EINVAL;
 	}
-	cpu = cpumask_first(&intersect_affinity);
 
 	vector = d->hwirq;
 	regaddr = EIOINTC_REG_ENABLE + ((vector >> 5) << 2);