[PATCH] check return value of cpu_callback

Spawing ksoftirqd, migration, or watchdog, and calling init_timers_cpu()
may fail with small memory.  If it happens in initcalls, kernel NULL
pointer dereference happens later.  This patch makes crash happen
immediately in such cases.  It seems a bit better than getting kernel NULL
pointer dereference later.

Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 11 insertions, 4 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 5c848fd4e461..b946209d9c15 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5272,9 +5272,11 @@ static struct notifier_block __cpuinitdata migration_notifier = {
 int __init migration_init(void)
 {
         void *cpu = (void *)(long)smp_processor_id();
+        int err;
 
         /* Start one for the boot CPU: */
-        migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
+        err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
+        BUG_ON(err == NOTIFY_BAD);
         migration_call(&migration_notifier, CPU_ONLINE, cpu);
         register_cpu_notifier(&migration_notifier);
 
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 3789ca98197c..bf25015dce16 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -612,7 +612,9 @@ static struct notifier_block __cpuinitdata cpu_nfb = {
 __init int spawn_ksoftirqd(void)
 {
         void *cpu = (void *)(long)smp_processor_id();
-        cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
+        int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
+
+        BUG_ON(err == NOTIFY_BAD);
         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
         register_cpu_notifier(&cpu_nfb);
         return 0;
diff --git a/kernel/softlockup.c b/kernel/softlockup.c
index 03e6a2b0b787..50afeb813305 100644
--- a/kernel/softlockup.c
+++ b/kernel/softlockup.c
@@ -149,8 +149,9 @@ static struct notifier_block __cpuinitdata cpu_nfb = {
 __init void spawn_softlockup_task(void)
 {
         void *cpu = (void *)(long)smp_processor_id();
+        int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
 
-        cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
+        BUG_ON(err == NOTIFY_BAD);
         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
         register_cpu_notifier(&cpu_nfb);
 
diff --git a/kernel/timer.c b/kernel/timer.c
index d644f4e9ca0c..a2cb1ecb1b28 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1694,8 +1694,10 @@ static struct notifier_block __cpuinitdata timers_nb = {
 
 void __init init_timers(void)
 {
-        timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
+        int err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
                                 (void *)(long)smp_processor_id());
+
+        BUG_ON(err == NOTIFY_BAD);
         register_cpu_notifier(&timers_nb);
         open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL);
 }