locking/csd_lock: Prepare more CSD lock debugging

In order to be able to easily add more CSD lock debugging data to
struct call_function_data->csd move the call_single_data_t element
into a sub-structure.
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210301101336.7797-3-jgross@suse.com

kernel/smp.c

@@ -31,8 +31,12 @@
 
 #define CSD_TYPE(_csd)	((_csd)->node.u_flags & CSD_FLAG_TYPE_MASK)
 
+struct cfd_percpu {
+	call_single_data_t	csd;
+};
+
 struct call_function_data {
-	call_single_data_t	__percpu *csd;
+	struct cfd_percpu	__percpu *pcpu;
 	cpumask_var_t		cpumask;
 	cpumask_var_t		cpumask_ipi;
 };
@@ -55,8 +59,8 @@ int smpcfd_prepare_cpu(unsigned int cpu)
 		free_cpumask_var(cfd->cpumask);
 		return -ENOMEM;
 	}
-	cfd->csd = alloc_percpu(call_single_data_t);
-	if (!cfd->csd) {
+	cfd->pcpu = alloc_percpu(struct cfd_percpu);
+	if (!cfd->pcpu) {
 		free_cpumask_var(cfd->cpumask);
 		free_cpumask_var(cfd->cpumask_ipi);
 		return -ENOMEM;
@@ -71,7 +75,7 @@ int smpcfd_dead_cpu(unsigned int cpu)
 
 	free_cpumask_var(cfd->cpumask);
 	free_cpumask_var(cfd->cpumask_ipi);
-	free_percpu(cfd->csd);
+	free_percpu(cfd->pcpu);
 	return 0;
 }
 
@@ -694,7 +698,7 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
 
 	cpumask_clear(cfd->cpumask_ipi);
 	for_each_cpu(cpu, cfd->cpumask) {
-		call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu);
+		call_single_data_t *csd = &per_cpu_ptr(cfd->pcpu, cpu)->csd;
 
 		if (cond_func && !cond_func(cpu, info))
 			continue;
@@ -719,7 +723,7 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
 		for_each_cpu(cpu, cfd->cpumask) {
 			call_single_data_t *csd;
 
-			csd = per_cpu_ptr(cfd->csd, cpu);
+			csd = &per_cpu_ptr(cfd->pcpu, cpu)->csd;
 			csd_lock_wait(csd);
 		}
 	}