linux-kernel - [PATCH 2/2] Better interface for hooking early initcalls.

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Date:	Sun, 15 Jun 2008 09:34:50 +0300
From:	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
To:	linux-kernel@...r.kernel.org
Cc:	penberg@...helsinki.fi, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org
Subject: [PATCH 2/2] Better interface for hooking early initcalls.

Added early initcall (pre-SMP) support, using an identical interface to
that of regular initcalls. This is required by CPU hotplug, because early
users have to register notifiers before going SMP. Functions called from
do_pre_smp_initcalls() could be converted to use this cleaner interface.

Signed-off-by: Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
---
 include/asm-generic/vmlinux.lds.h |    2 ++
 include/linux/init.h              |    7 +++++++
 init/main.c                       |   13 +++++++++++--
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index f054778..4a318e5 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -326,6 +326,8 @@
 	}
 
 #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 21d658c..bd12a4c 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -170,6 +170,13 @@ extern void (*late_time_init)(void);
 	__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 5bc79e5..fbae22f 100644
--- a/init/main.c
+++ b/init/main.c
@@ -738,13 +738,13 @@ 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 */
@@ -777,6 +777,14 @@ 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++)
+		(*call)();
+}
+
 static void __init do_pre_smp_initcalls(void)
 {
 	extern int spawn_ksoftirqd(void);
@@ -858,6 +866,7 @@ static int __init kernel_init(void * unused)
 
 	smp_prepare_cpus(setup_max_cpus);
 
+	__do_pre_smp_initcalls();
 	do_pre_smp_initcalls();
 
 	smp_init();
-- 
1.5.5.4
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