Better interface for hooking early initcalls

Added early initcall (pre-SMP) support, using an identical interface to
that of regular initcalls.  Functions called from do_pre_smp_initcalls()
could be converted to use this cleaner interface.

This is required by CPU hotplug, because early users have to register
notifiers before going SMP.  One such CPU hotplug user is the relay
interface with buffer-only channels, which needs to register such a
notifier, to be usable in early code.  This in turn is used by kmemtrace.

Signed-off-by: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Cc: Tom Zanussi <tzanussi@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 729f6b0a60e9d1655cfa5005236c5bf11fb83d5c..9cd44b162ba1809af8d28093da19b353f7be7cd0 100644 (file)
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -359,6 +359,8 @@
        }
 
 #define INITCALLS                                                      \
+       *(.initcallearly.init)                                          \
+       __early_initcall_end = .;                                       \
        *(.initcall0.init)                                              \
        *(.initcall0s.init)                                             \
        *(.initcall1.init)                                              \

diff --git a/include/linux/init.h b/include/linux/init.h
index 42ae95411a93510433c25c31b03b0b28f095869c..11b84e1060532ecf62f73e3151b9f6eaed043c8b 100644 (file)
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -169,6 +169,13 @@ extern void (*late_time_init)(void);
        static initcall_t __initcall_##fn##id __used \
        __attribute__((__section__(".initcall" level ".init"))) = fn
 
+/*
+ * Early initcalls run before initializing SMP.
+ *
+ * Only for built-in code, not modules.
+ */
+#define early_initcall(fn)             __define_initcall("early",fn,early)
+
 /*
  * A "pure" initcall has no dependencies on anything else, and purely
  * initializes variables that couldn't be statically initialized.

diff --git a/init/main.c b/init/main.c
index 0604cbcaf1e4e2030f487e663966cba66517101b..b6fec08dbbef65236edd042b7834be771de6faf0 100644 (file)
--- a/init/main.c
+++ b/init/main.c
@@ -743,13 +743,13 @@ static void __init do_one_initcall(initcall_t fn)
 }
 
 
-extern initcall_t __initcall_start[], __initcall_end[];
+extern initcall_t __initcall_start[], __initcall_end[], __early_initcall_end[];
 
 static void __init do_initcalls(void)
 {
        initcall_t *call;
 
-       for (call = __initcall_start; call < __initcall_end; call++)
+       for (call = __early_initcall_end; call < __initcall_end; call++)
                do_one_initcall(*call);
 
        /* Make sure there is no pending stuff from the initcall sequence */
@@ -783,6 +783,14 @@ static int __init nosoftlockup_setup(char *str)
 }
 __setup("nosoftlockup", nosoftlockup_setup);
 
+static void __init __do_pre_smp_initcalls(void)
+{
+       initcall_t *call;
+
+       for (call = __initcall_start; call < __early_initcall_end; call++)
+               do_one_initcall(*call);
+}
+
 static void __init do_pre_smp_initcalls(void)
 {
        extern int spawn_ksoftirqd(void);
@@ -865,6 +873,7 @@ static int __init kernel_init(void * unused)
 
        smp_prepare_cpus(setup_max_cpus);
 
+       __do_pre_smp_initcalls();
        do_pre_smp_initcalls();
 
        smp_init();