[PATCH] irqchip/gic: add WARN_ON() to facilitate backtracking

[PATCH] irqchip/gic: add WARN_ON() to facilitate backtracking

[Yejune Deng]

There is two function gic_of_init() and gic_of_init_child() called
gic_of_setup(),so add WARN_ON() to facilitate backtracking.

Signed-off-by: Yejune Deng <yejune.deng@gmail.com>
---
 drivers/irqchip/irq-gic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
index b1d9c22..7c11705 100644
--- a/drivers/irqchip/irq-gic.c
+++ b/drivers/irqchip/irq-gic.c
@@ -1380,7 +1380,7 @@ static bool gic_check_eoimode(struct device_node *node, void __iomem **base)
 
 static int gic_of_setup(struct gic_chip_data *gic, struct device_node *node)
 {
-	if (!gic || !node)
+	if (WARN_ON(!gic || !node))
 		return -EINVAL;
 
 	gic->raw_dist_base = of_iomap(node, 0);
-- 
1.9.1

Re: [PATCH] irqchip/gic: add WARN_ON() to facilitate backtracking

[Marc Zyngier]

Yejune,

On 2020-12-29 07:15, Yejune Deng wrote:
> There is two function gic_of_init() and gic_of_init_child() called
> gic_of_setup(),so add WARN_ON() to facilitate backtracking.
> 
> Signed-off-by: Yejune Deng <yejune.deng@gmail.com>
> ---
>  drivers/irqchip/irq-gic.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
> index b1d9c22..7c11705 100644
> --- a/drivers/irqchip/irq-gic.c
> +++ b/drivers/irqchip/irq-gic.c
> @@ -1380,7 +1380,7 @@ static bool gic_check_eoimode(struct device_node
> *node, void __iomem **base)
> 
>  static int gic_of_setup(struct gic_chip_data *gic, struct device_node 
> *node)
>  {
> -	if (!gic || !node)
> +	if (WARN_ON(!gic || !node))
>  		return -EINVAL;
> 
>  	gic->raw_dist_base = of_iomap(node, 0);

I don't immediately see what you gain with this. If you end-up here
with NULL pointers, that either because:

- you have failed to allocate the GIC private data structure:
   but as it turns out, these allocations either cannot fail (gic_data[]
   is static), or the dynamic allocation in gic_of_init_child() is 
already
   checked.

- node is NULL: both paths already check for a NULL node, so that cannot
   fail either.

My conclusion is that these checks can never trigger, and we should be
able to *remove* them altogether.

Am I missing something?

         M.
-- 
Jazz is not dead. It just smells funny...

Re: [PATCH] irqchip/gic: add WARN_ON() to facilitate backtracking

[Yejune Deng]

OK，I will adopt it and resubmit.

On Tue, Dec 29, 2020 at 5:27 PM Marc Zyngier <maz@kernel.org> wrote:
>
> Yejune,
>
> On 2020-12-29 07:15, Yejune Deng wrote:
> > There is two function gic_of_init() and gic_of_init_child() called
> > gic_of_setup(),so add WARN_ON() to facilitate backtracking.
> >
> > Signed-off-by: Yejune Deng <yejune.deng@gmail.com>
> > ---
> >  drivers/irqchip/irq-gic.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
> > index b1d9c22..7c11705 100644
> > --- a/drivers/irqchip/irq-gic.c
> > +++ b/drivers/irqchip/irq-gic.c
> > @@ -1380,7 +1380,7 @@ static bool gic_check_eoimode(struct device_node
> > *node, void __iomem **base)
> >
> >  static int gic_of_setup(struct gic_chip_data *gic, struct device_node
> > *node)
> >  {
> > -     if (!gic || !node)
> > +     if (WARN_ON(!gic || !node))
> >               return -EINVAL;
> >
> >       gic->raw_dist_base = of_iomap(node, 0);
>
> I don't immediately see what you gain with this. If you end-up here
> with NULL pointers, that either because:
>
> - you have failed to allocate the GIC private data structure:
>    but as it turns out, these allocations either cannot fail (gic_data[]
>    is static), or the dynamic allocation in gic_of_init_child() is
> already
>    checked.
>
> - node is NULL: both paths already check for a NULL node, so that cannot
>    fail either.
>
> My conclusion is that these checks can never trigger, and we should be
> able to *remove* them altogether.
>
> Am I missing something?
>
>          M.
> --
> Jazz is not dead. It just smells funny...