Re: [PATCH 2/8] dynamic debug - core infrastructure

Joe Perches
2008-06-13T22:31:51Z

On Fri, 2008-06-13 at 15:00 -0400, Jason Baron wrote:
> This is the core patch that implements a new dynamic debug
> infrastructure.

Some general and specific comments.

> +int dynamic_printk_enabled[NR_CPUS];

I don't understand why you use NR_CPUS.

Also, I think the major use cases are 1 or 2 modules enabled,
no modules enabled, or all modules enabled, so the hashing of
module names is particularly not useful.

Any pr_debug or dev_dbg is in a slow path.

I think a list and a direct comparison to KBUILD_MODNAME
would be simpler and as fast as necessary.

> + To set the level or flag value for type 'level' or 'flag':
> +
> + $echo "set level=<#> <module_name>" > dynamic_printk/modules
> +

I think that set level=<#> should also work for "all"

Perhaps a simpler interface would be to use
enable <module> <level>
where <level> not specified is 0.

> +int unregister_debug_module(char *mod_name)
> +{
> + struct debug_name *element;
> + struct debug_name *parent = NULL;
> + int ret = 0;
> + int i;
> +
> + down(&debug_list_mutex);
> + element = find_debug_module(mod_name);
> + if (!element) {
> + ret = -EINVAL;
> + goto out;
> + }

[]

> +out:
> + up(&debug_list_mutex);
> + return 0;
> +}

Because the return values aren't used,
the functions might as well be declared void

You should probably add a sprinkling of "const"
to the argument lists.

+extern void dynamic_printk(char *, char *, ...);

+ dynamic_printk(KBUILD_MODNAME, \
+ KERN_DEBUG KBUILD_MODNAME ": " fmt,\

Instead of prefixing every fmt with KBUILD_MODNAME ": ",
why not change this to something like:

extern void dynamic_printk(const char *level, const char *module,
const char *fmt, ...);

and just do the printk in 2 parts?

if (module_enabled) {
printk("%s%s: ", level, module);
vprintk(fmt, args);
}

If not that, why should dynamic_printk prefix a KBUILD_MODNAME
at all? Why not just check if the module is enabled, then
output what the code specifies?

trivial: The dynamic versions of the dev_dbg and pr_debug macros
don't return the number of chars output, but always return 0.