Re: [PATCH] sysctl: Add a group of macro functions to initcall the sysctl table of each feature

[Xiaoming Ni]

On 2021/12/7 9:50, Joe Perches wrote:
> On Mon, 2021-12-06 at 17:38 -0800, Andrew Morton wrote:
> > On Tue, 7 Dec 2021 09:13:20 +0800 Xiaoming Ni <nixiaoming@xxxxxxxxxx> wrote:
> >
> > > To avoid duplicated code, add a set of macro functions to initialize the
> > > sysctl table for each feature.
> > >
> > > The system initialization process is as follows:
> > >
> > > 	start_kernel () {
> > > 		...
> > > 		/* init proc and sysctl base,
> > > 		 * proc_root_init()-->proc_sys_init()-->sysctl_init_bases()
> > > 		 */
> > > 		proc_root_init(); /* init proc and sysctl base */
> > > 		...
> > > 		arch_call_rest_init();
> > > 	}
> > >
> > > 	arch_call_rest_init()-->rest_init()-->kernel_init()
> > > 	kernel_init() {
> > > 		...
> > > 		kernel_init_freeable(); /* do all initcalls */
> > > 		...
> > > 		do_sysctl_args(); /* Process the sysctl parameter: sysctl.*= */
> > > 	}
> > >
> > > 	kernel_init_freeable()--->do_basic_setup()-->do_initcalls()
> > > 	do_initcalls() {
> > > 		for (level = 0; level < ARRAY_SIZE(initcall_levels) - 1; level++) {
> > > 			do_initcall_level
> > > 	}
> > >
> > > The sysctl interface of each subfeature should be registered after
> > > sysctl_init_bases() and before do_sysctl_args(). It seems that the sysctl
> > > interface does not depend on initcall_levels. To prevent the sysctl
> > > interface from being initialized before the feature itself. The
> > > lowest-level late_initcall() is used as the common sysctl interface
> > > registration level.
> >
> > I'm not normally a fan of wrapping commonly-used code sequences into
> > magical macros, but this one does seem to make sense.
> >
> > I wonder if it is possible to cook up a checkpatch rule to tell people
> > to henceforth use the magic macros rather than to open-code things in
> > the old way.  Sounds hard.
>
> Almost impossible for checkpatch.
> Likely easier in coccinelle.

Maybe we can add a rudimentary check to the checkpatch.

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index b01c36a15d9d..26e953ae4cc5 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -7212,6 +7212,12 @@ sub process {
                             "Deprecated use of '$deprecated_api', 
prefer '$new_api' instead\n" . $herecurr);
                }

+# check register_sysctl_init
+               if ($prevline =~ /{/ && $rawline =~ 
/\sregister_sysctl_init\(\"(kernel|fs|vm|debug|dev)\",\s+(.*)\)\;/) {
+                       WARN("DEPRECATED_API",
+                            "Deprecated use of 
'register_sysctl_init(\"$1\", $2);', prefer '$1_sysctl_initcall($2);' 
instead\n".$herecurr);
+               }
+
 # check for various structs that are normally const (ops, kgdb, 
device_tree)
 # and avoid what seem like struct definitions 'struct foo {'
                if (defined($const_structs) &&



Thanks
Xiaoming Ni