2020-08-07 08:37:53

by Daniel Almeida

Subject: [PATCH 08/20] media: pci: saa7164.c: Replace if(cond) BUG with BUG_ON

From: "Daniel W. S. Almeida" <[email protected]>

Fix the following coccinelle reports:

drivers/media/pci/saa7164/saa7164-buffer.c:254:3-6: WARNING: Use BUG_ON
instead of if condition followed by BUG.

drivers/media/pci/saa7164/saa7164-buffer.c:261:3-6: WARNING: Use BUG_ON
instead of if condition followed by BUG.

Found using - Coccinelle (http://coccinelle.lip6.fr)

Signed-off-by: Daniel W. S. Almeida <[email protected]>
---
drivers/media/pci/saa7164/saa7164-buffer.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/media/pci/saa7164/saa7164-buffer.c b/drivers/media/pci/saa7164/saa7164-buffer.c
index 289cb901985b..245d9db280aa 100644
--- a/drivers/media/pci/saa7164/saa7164-buffer.c
+++ b/drivers/media/pci/saa7164/saa7164-buffer.c
@@ -250,15 +250,14 @@ int saa7164_buffer_cfg_port(struct saa7164_port *port)
list_for_each_safe(c, n, &port->dmaqueue.list) {
buf = list_entry(c, struct saa7164_buffer, list);

- if (buf->flags != SAA7164_BUFFER_FREE)
- BUG();
+ BUG_ON(buf->flags != SAA7164_BUFFER_FREE);

/* Place the buffer in the h/w queue */
saa7164_buffer_activate(buf, i);

/* Don't exceed the device maximum # bufs */
- if (i++ > port->hwcfg.buffercount)
- BUG();
+ BUG_ON(i > port->hwcfg.buffercount);
+ i++;

}
mutex_unlock(&port->dmaqueue_lock);
@@ -302,4 +301,3 @@ void saa7164_buffer_dealloc_user(struct saa7164_user_buffer *buf)

kfree(buf);
}
-
--
2.28.0

2020-08-29 06:45:44

by Mauro Carvalho Chehab

Subject: Re: [PATCH 08/20] media: pci: saa7164.c: Replace if(cond) BUG with BUG_ON

Hi Daniel,

Em Fri, 7 Aug 2020 05:35:35 -0300
"Daniel W. S. Almeida" <[email protected]> escreveu:

> From: "Daniel W. S. Almeida" <[email protected]>
>
> Fix the following coccinelle reports:
>
> drivers/media/pci/saa7164/saa7164-buffer.c:254:3-6: WARNING: Use BUG_ON
> instead of if condition followed by BUG.
>
> drivers/media/pci/saa7164/saa7164-buffer.c:261:3-6: WARNING: Use BUG_ON
> instead of if condition followed by BUG.
>
> Found using - Coccinelle (http://coccinelle.lip6.fr)

I ended accepting those patches, but IMO, this doesn't make
the code any better.

The thing is that very few parts of the Kernel should panic if
things go sideways. I don't think that any media driver would
apply on such cases.

As pointed at:

https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

The real fix is to use WARN_ON(), probably with something like:

if (WARN_ON(something))
return;

as probably the code after BUG() would be assuming that the
condition was asserted.

Regards,
Mauro

>
> Signed-off-by: Daniel W. S. Almeida <[email protected]>
> ---
> drivers/media/pci/saa7164/saa7164-buffer.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/media/pci/saa7164/saa7164-buffer.c b/drivers/media/pci/saa7164/saa7164-buffer.c
> index 289cb901985b..245d9db280aa 100644
> --- a/drivers/media/pci/saa7164/saa7164-buffer.c
> +++ b/drivers/media/pci/saa7164/saa7164-buffer.c
> @@ -250,15 +250,14 @@ int saa7164_buffer_cfg_port(struct saa7164_port *port)
> list_for_each_safe(c, n, &port->dmaqueue.list) {
> buf = list_entry(c, struct saa7164_buffer, list);
>
> - if (buf->flags != SAA7164_BUFFER_FREE)
> - BUG();
> + BUG_ON(buf->flags != SAA7164_BUFFER_FREE);
>
> /* Place the buffer in the h/w queue */
> saa7164_buffer_activate(buf, i);
>
> /* Don't exceed the device maximum # bufs */
> - if (i++ > port->hwcfg.buffercount)
> - BUG();
> + BUG_ON(i > port->hwcfg.buffercount);
> + i++;
>
> }
> mutex_unlock(&port->dmaqueue_lock);
> @@ -302,4 +301,3 @@ void saa7164_buffer_dealloc_user(struct saa7164_user_buffer *buf)
>
> kfree(buf);
> }
> -



Thanks,
Mauro