Subject: revert stop_machine: Provide stop_machine_cpuslocked()
From: Mike Galbraith <mgalbraith@suse.de>
Date: Wed Aug 22 07:33:59 CEST 2018
Patch-mainline: Never, -rt specific
References: SLE Realtime Extension

Part of massive/complex/validated RT all-in-one hotplug update.

Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
---
 include/linux/stop_machine.h | 26 +++-----------------------
 kernel/stop_machine.c        | 11 ++++-------
 2 files changed, 7 insertions(+), 30 deletions(-)

--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -116,29 +116,15 @@ static inline int try_stop_cpus(const st
  * @fn() runs.
  *
  * This can be thought of as a very heavy write lock, equivalent to
- * grabbing every spinlock in the kernel.
- *
- * Protects against CPU hotplug.
- */
+ * grabbing every spinlock in the kernel. */
 int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
 
-/**
- * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
- * @fn: the function to run
- * @data: the data ptr for the @fn()
- * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
- *
- * Same as above. Must be called from with in a cpus_read_lock() protected
- * region. Avoids nested calls to cpus_read_lock().
- */
-int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
-
 int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 				   const struct cpumask *cpus);
 #else	/* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
 
-static __always_inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
-					  const struct cpumask *cpus)
+static __always_inline int stop_machine(cpu_stop_fn_t fn, void *data,
+					const struct cpumask *cpus)
 {
 	unsigned long flags;
 	int ret;
@@ -149,12 +135,6 @@ static __always_inline int stop_machine_
 }
 
 static __always_inline int
-stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
-{
-	return stop_machine_cpuslocked(fn, data, cpus);
-}
-
-static __always_inline int
 stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 			       const struct cpumask *cpus)
 {
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -575,8 +575,7 @@ static int __init cpu_stop_init(void)
 }
 early_initcall(cpu_stop_init);
 
-int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
-			    const struct cpumask *cpus)
+static int __stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
 {
 	struct multi_stop_data msdata = {
 		.fn = fn,
@@ -585,8 +584,6 @@ int stop_machine_cpuslocked(cpu_stop_fn_
 		.active_cpus = cpus,
 	};
 
-	lockdep_assert_cpus_held();
-
 	if (!stop_machine_initialized) {
 		/*
 		 * Handle the case where stop_machine() is called
@@ -616,9 +613,9 @@ int stop_machine(cpu_stop_fn_t fn, void
 	int ret;
 
 	/* No CPUs can come up or down during this. */
-	cpus_read_lock();
-	ret = stop_machine_cpuslocked(fn, data, cpus);
-	cpus_read_unlock();
+	get_online_cpus();
+	ret = __stop_machine(fn, data, cpus);
+	put_online_cpus();
 	return ret;
 }
 EXPORT_SYMBOL_GPL(stop_machine);