linux-kernel - Re: [PATCH v1 1/1] panic: Fix compilation error (`make W=1`)

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Message-ID: <aHCpbB7cfwfdFBzl@smile.fi.intel.com>
Date: Fri, 11 Jul 2025 09:04:28 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Feng Tang <feng.tang@...ux.alibaba.com>
Cc: Nathan Chancellor <nathan@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Petr Mladek <pmladek@...e.com>
Subject: Re: [PATCH v1 1/1] panic: Fix compilation error (`make W=1`)

On Fri, Jul 11, 2025 at 10:48:29AM +0800, Feng Tang wrote:
> On Thu, Jul 10, 2025 at 06:49:47PM -0700, Nathan Chancellor wrote:
> > On Fri, Jul 11, 2025 at 08:54:25AM +0800, Feng Tang wrote:
> > > On Thu, Jul 10, 2025 at 03:01:33PM -0700, Andrew Morton wrote:
> > > > On Thu, 10 Jul 2025 12:48:16 +0300 Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

...

> > > sys_info_avail[] has another purpose for being a counterpart of si_names[],
> > > which could be extended in future, so we make it obviously stand-alone. As
> > > for definition of si_names[], we explicitly added comment:  
> > > 
> > > 	/*
> > > 	 * When 'si_names' gets updated,  please make sure the 'sys_info_avail'
> > > 	 * below is updated accordingly.
> > > 	 */
> > > 	static const struct sys_info_name  si_names[] = {
> > > 		{ SYS_INFO_TASKS,		"tasks" },
> > > 		{ SYS_INFO_MEM,			"mem" },
> > > 		
> > > which has also been discussed in another thread:
> > > https://lore.kernel.org/lkml/aG3o2RFHc5iXnJef@U-2FWC9VHC-2323.local/
> > > 
> > > And I suggest to keep sys_info_avail[], and either Nathan or Sergey's patch
> > > works for me.
> > 
> > We could do something like this to keep the sizeof() obvious and
> > separate, while still eliminating the variable? Happy to bike shed
> > aspects of it like the macro name and such.

...

> > +#define SYS_INFO_MAX_LEN (sizeof("tasks,mem,timers,locks,ftrace,all_bt,blocked_tasks") + 1)

The ' + 1' is batter to leave for the names below.
Or at bare minimum it needs a semantic explanation.
If it's for NUL, definitely shouldn't be part of the
definition.

> >  int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
> >  					  void *buffer, size_t *lenp,
> >  					  loff_t *ppos)
> >  {
> > -	char names[sizeof(sys_info_avail) + 1];
> > +	char names[SYS_INFO_MAX_LEN];
> >  	struct ctl_table table;
> >  	unsigned long *si_bits_global;
>   
> Looks great to me, thanks!
> 
> We can even move the SYS_INFO_MAX_LEN definition close to si_names[],

Agree.

> initially sys_info_avail[] was next to si_names[], and was moved inside 
> "#ifdef CONFIG_SYSCTL" region for compiling CONFIG_SYSCTL=n case.

But let me think a bit, perhaps we can come up with something even better.

-- 
With Best Regards,
Andy Shevchenko