Messages in this thread | | | Subject | Re: [PATCH] sysctl: Add a group of macro functions to initcall the sysctl table of each feature | From | Xiaoming Ni <> | Date | Tue, 7 Dec 2021 11:09:47 +0800 |
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On 2021/12/7 9:38, Andrew Morton wrote: > On Tue, 7 Dec 2021 09:13:20 +0800 Xiaoming Ni <nixiaoming@huawei.com> 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. > >> --- a/fs/coredump.c >> +++ b/fs/coredump.c >> @@ -943,12 +943,7 @@ static struct ctl_table coredump_sysctls[] = { >> { } >> }; >> >> -static int __init init_fs_coredump_sysctls(void) >> -{ >> - register_sysctl_init("kernel", coredump_sysctls); >> - return 0; >> -} >> -fs_initcall(init_fs_coredump_sysctls); >> +kernel_sysctl_initcall(coredump_sysctls); > > But this and several like it are functional changes. > >> #endif /* CONFIG_SYSCTL */ >> >> ... >> >> --- a/fs/inode.c >> +++ b/fs/inode.c >> @@ -132,12 +132,7 @@ static struct ctl_table inodes_sysctls[] = { >> { } >> }; >> >> -static int __init init_fs_inode_sysctls(void) >> -{ >> - register_sysctl_init("fs", inodes_sysctls); >> - return 0; >> -} >> -early_initcall(init_fs_inode_sysctls); >> +fs_sysctl_initcall(inodes_sysctls); >> #endif > > Here's another, of many. > > Someone made the decision to use early_initcall() here (why?) and this > patch switches it to late_initcall()! Worrisome. Each such stealth > conversion should be explained and justified, shouldn't it? >
static noinline void __init kernel_init_freeable(void) { ... do_pre_smp_initcalls(); /* do early_initcall */ lockup_detector_init();
smp_init(); sched_init_smp();
padata_init(); page_alloc_init_late(); /* Initialize page ext after all struct pages are initialized. */ page_ext_init();
do_basic_setup(); /* do other initcall */ ... }
Between do_pre_smp_initcalls() and do_basic_setup(), no sysctl interface window is configured. In addition, all sysctl data has initial values. Delayed configuration does not affect the behavior after startup. So I think we can change it to late_initcall().
Thanks Xiaoming Ni
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