mm/init: cpu_hotplug_init() must be initialized before SLAB

SLAB uses get/put_online_cpus() which use a mutex which is itself only initialized when cpu_hotplug_init() is called. Currently we hang suring boot in SLAB due to doing that too late. Reported by James Bottomley and Sachin Sant (and possibly others). Debugged by Benjamin Herrenschmidt. This just removes the dynamic initialization of the data structures, and replaces it with a static one, avoiding this dependency entirely, and removing one unnecessary special initcall. Tested-by: Sachin Sant <[email protected]> Tested-by: James Bottomley <[email protected]> Tested-by: Benjamin Herrenschmidt <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
yshchan · Jun 23, 2009 · 31950eb · 31950eb
1 parent ac1b7c3
commit 31950eb
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Showing 3 changed files with 5 additions and 14 deletions.
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
@@ -69,7 +69,6 @@ static inline void unregister_cpu_notifier(struct notifier_block *nb)
 
 int cpu_up(unsigned int cpu);
 void notify_cpu_starting(unsigned int cpu);
-extern void cpu_hotplug_init(void);
 extern void cpu_maps_update_begin(void);
 extern void cpu_maps_update_done(void);
 
@@ -84,10 +83,6 @@ static inline void unregister_cpu_notifier(struct notifier_block *nb)
 {
 }
 
-static inline void cpu_hotplug_init(void)
-{
-}
-
 static inline void cpu_maps_update_begin(void)
 {
 }

diff --git a/init/main.c b/init/main.c
@@ -678,7 +678,6 @@ asmlinkage void __init start_kernel(void)
 #endif
 	page_cgroup_init();
 	enable_debug_pagealloc();
-	cpu_hotplug_init();
 	kmemtrace_init();
 	kmemleak_init();
 	debug_objects_mem_init();

diff --git a/kernel/cpu.c b/kernel/cpu.c
@@ -34,14 +34,11 @@ static struct {
 	 * an ongoing cpu hotplug operation.
 	 */
 	int refcount;
-} cpu_hotplug;
-
-void __init cpu_hotplug_init(void)
-{
-	cpu_hotplug.active_writer = NULL;
-	mutex_init(&cpu_hotplug.lock);
-	cpu_hotplug.refcount = 0;
-}
+} cpu_hotplug = {
+	.active_writer = NULL,
+	.lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
+	.refcount = 0,
+};
 
 #ifdef CONFIG_HOTPLUG_CPU