[S390] smp: __smp_call_function_map vs cpu_online_map fix.

Both smp_call_function() and __smp_call_function_map() access
cpu_online_map. Both functions run with preemption disabled which
protects for cpus going offline. However new cpus can be added and
therefore the cpu_online_map can change unexpectedly.
So use the call_lock to protect against changes to the cpu_online_map
in start_secondary() and all smp_call_* functions.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 0aeb290..1f42289 100644 (file)
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -139,7 +139,6 @@ static void __smp_call_function_map(void (*func) (void *info), void *info,
        if (wait)
                data.finished = CPU_MASK_NONE;
 
-       spin_lock(&call_lock);
        call_data = &data;
 
        for_each_cpu_mask(cpu, map)
@@ -151,7 +150,6 @@ static void __smp_call_function_map(void (*func) (void *info), void *info,
        if (wait)
                while (!cpus_equal(map, data.finished))
                        cpu_relax();
-       spin_unlock(&call_lock);
 out:
        if (local) {
                local_irq_disable();
@@ -177,11 +175,11 @@ int smp_call_function(void (*func) (void *info), void *info, int nonatomic,
 {
        cpumask_t map;
 
-       preempt_disable();
+       spin_lock(&call_lock);
        map = cpu_online_map;
        cpu_clear(smp_processor_id(), map);
        __smp_call_function_map(func, info, nonatomic, wait, map);
-       preempt_enable();
+       spin_unlock(&call_lock);
        return 0;
 }
 EXPORT_SYMBOL(smp_call_function);
@@ -202,10 +200,10 @@ EXPORT_SYMBOL(smp_call_function);
 int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
                             int nonatomic, int wait)
 {
-       preempt_disable();
+       spin_lock(&call_lock);
        __smp_call_function_map(func, info, nonatomic, wait,
                                cpumask_of_cpu(cpu));
-       preempt_enable();
+       spin_unlock(&call_lock);
        return 0;
 }
 EXPORT_SYMBOL(smp_call_function_single);
@@ -228,10 +226,10 @@ EXPORT_SYMBOL(smp_call_function_single);
 int smp_call_function_mask(cpumask_t mask, void (*func)(void *), void *info,
                           int wait)
 {
-       preempt_disable();
+       spin_lock(&call_lock);
        cpu_clear(smp_processor_id(), mask);
        __smp_call_function_map(func, info, 0, wait, mask);
-       preempt_enable();
+       spin_unlock(&call_lock);
        return 0;
 }
 EXPORT_SYMBOL(smp_call_function_mask);
@@ -592,7 +590,9 @@ int __cpuinit start_secondary(void *cpuvoid)
        pfault_init();
 
        /* Mark this cpu as online */
+       spin_lock(&call_lock);
        cpu_set(smp_processor_id(), cpu_online_map);
+       spin_unlock(&call_lock);
        /* Switch on interrupts */
        local_irq_enable();
        /* Print info about this processor */