1 files changed, 73 insertions, 5 deletions

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index e3516b29076c..c1124752e1d3 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -136,10 +136,11 @@ void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
 static DEFINE_MUTEX(stop_cpus_mutex);
 static DEFINE_PER_CPU(struct cpu_stop_work, stop_cpus_work);
 
-int __stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
+static void queue_stop_cpus_work(const struct cpumask *cpumask,
+				 cpu_stop_fn_t fn, void *arg,
+				 struct cpu_stop_done *done)
 {
 	struct cpu_stop_work *work;
-	struct cpu_stop_done done;
 	unsigned int cpu;
 
 	/* initialize works and done */
@@ -147,9 +148,8 @@ int __stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
 		work = &per_cpu(stop_cpus_work, cpu);
 		work->fn = fn;
 		work->arg = arg;
-		work->done = &done;
+		work->done = done;
 	}
-	cpu_stop_init_done(&done, cpumask_weight(cpumask));
 
 	/*
 	 * Disable preemption while queueing to avoid getting
@@ -161,7 +161,15 @@ int __stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
 		cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu),
 				    &per_cpu(stop_cpus_work, cpu));
 	preempt_enable();
+}
 
+static int __stop_cpus(const struct cpumask *cpumask,
+		       cpu_stop_fn_t fn, void *arg)
+{
+	struct cpu_stop_done done;
+
+	cpu_stop_init_done(&done, cpumask_weight(cpumask));
+	queue_stop_cpus_work(cpumask, fn, arg, &done);
 	wait_for_completion(&done.completion);
 	return done.executed ? done.ret : -ENOENT;
 }
@@ -431,8 +439,15 @@ static int stop_machine_cpu_stop(void *data)
 	struct stop_machine_data *smdata = data;
 	enum stopmachine_state curstate = STOPMACHINE_NONE;
 	int cpu = smp_processor_id(), err = 0;
+	unsigned long flags;
 	bool is_active;
 
+	/*
+	 * When called from stop_machine_from_inactive_cpu(), irq might
+	 * already be disabled.  Save the state and restore it on exit.
+	 */
+	local_save_flags(flags);
+
 	if (!smdata->active_cpus)
 		is_active = cpu == cpumask_first(cpu_online_mask);
 	else
@@ -460,7 +475,7 @@ static int stop_machine_cpu_stop(void *data)
 		}
 	} while (curstate != STOPMACHINE_EXIT);
 
-	local_irq_enable();
+	local_irq_restore(flags);
 	return err;
 }
 
@@ -487,4 +502,57 @@ int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
 }
 EXPORT_SYMBOL_GPL(stop_machine);
 
+/**
+ * stop_machine_from_inactive_cpu - stop_machine() from inactive CPU
+ * @fn: the function to run
+ * @data: the data ptr for the @fn()
+ * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
+ *
+ * This is identical to stop_machine() but can be called from a CPU which
+ * is not active.  The local CPU is in the process of hotplug (so no other
+ * CPU hotplug can start) and not marked active and doesn't have enough
+ * context to sleep.
+ *
+ * This function provides stop_machine() functionality for such state by
+ * using busy-wait for synchronization and executing @fn directly for local
+ * CPU.
+ *
+ * CONTEXT:
+ * Local CPU is inactive.  Temporarily stops all active CPUs.
+ *
+ * RETURNS:
+ * 0 if all executions of @fn returned 0, any non zero return value if any
+ * returned non zero.
+ */
+int stop_machine_from_inactive_cpu(int (*fn)(void *), void *data,
+				  const struct cpumask *cpus)
+{
+	struct stop_machine_data smdata = { .fn = fn, .data = data,
+					    .active_cpus = cpus };
+	struct cpu_stop_done done;
+	int ret;
+
+	/* Local CPU must be inactive and CPU hotplug in progress. */
+	BUG_ON(cpu_active(raw_smp_processor_id()));
+	smdata.num_threads = num_active_cpus() + 1;	/* +1 for local */
+
+	/* No proper task established and can't sleep - busy wait for lock. */
+	while (!mutex_trylock(&stop_cpus_mutex))
+		cpu_relax();
+
+	/* Schedule work on other CPUs and execute directly for local CPU */
+	set_state(&smdata, STOPMACHINE_PREPARE);
+	cpu_stop_init_done(&done, num_active_cpus());
+	queue_stop_cpus_work(cpu_active_mask, stop_machine_cpu_stop, &smdata,
+			     &done);
+	ret = stop_machine_cpu_stop(&smdata);
+
+	/* Busy wait for completion. */
+	while (!completion_done(&done.completion))
+		cpu_relax();
+
+	mutex_unlock(&stop_cpus_mutex);
+	return ret ?: done.ret;
+}
+
 #endif	/* CONFIG_STOP_MACHINE */