ANDROID: stop_machine: stop_one_cpu_async

This new interface allows to trigger a stopper on a given CPU and wait
for the end of the work in a separated function cpu_stop_work_wait().

This differs from stop_one_cpu_nowait() by allowing the usage of the
cpu_stop completion mechanism.

Bug: 161210528
Change-Id: Ida51371e32897d008ece0639190fc21feabb0f28
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>

include/linux/stop_machine.h

@@ -28,6 +28,16 @@ struct cpu_stop_work {
 	struct cpu_stop_done	*done;
 };
 
+/*
+ * Structure to determine completion condition and record errors.  May
+ * be shared by works on different cpus.
+ */
+struct cpu_stop_done {
+	atomic_t		nr_todo;	/* nr left to execute */
+	int			ret;		/* collected return value */
+	struct completion	completion;	/* fired if nr_todo reaches 0 */
+};
+
 int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
 int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
 bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
@@ -35,6 +45,10 @@ bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
 void stop_machine_park(int cpu);
 void stop_machine_unpark(int cpu);
 void stop_machine_yield(const struct cpumask *cpumask);
+int stop_one_cpu_async(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
+		       struct cpu_stop_work *work_buf,
+		       struct cpu_stop_done *done);
+void cpu_stop_work_wait(struct cpu_stop_work *work_buf);
 
 #else	/* CONFIG_SMP */
 

kernel/stop_machine.c

@@ -22,16 +22,7 @@
 #include <linux/atomic.h>
 #include <linux/nmi.h>
 #include <linux/sched/wake_q.h>
-
+#include <linux/slab.h>
-/*
- * Structure to determine completion condition and record errors.  May
- * be shared by works on different cpus.
- */
-struct cpu_stop_done {
-	atomic_t		nr_todo;	/* nr left to execute */
-	int			ret;		/* collected return value */
-	struct completion	completion;	/* fired if nr_todo reaches 0 */
-};
 
 /* the actual stopper, one per every possible cpu, enabled on online cpus */
 struct cpu_stopper {
@@ -372,6 +363,54 @@ bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
 }
 EXPORT_SYMBOL_GPL(stop_one_cpu_nowait);
 
+/**
+ * stop_one_cpu_async - stop a cpu and wait for completion in a separated
+ *			function: stop_wait_work()
+ * @cpu: cpu to stop
+ * @fn: function to execute
+ * @arg: argument to @fn
+ * @work_buf: pointer to cpu_stop_work structure
+ *
+ * CONTEXT:
+ * Might sleep.
+ *
+ * RETURNS:
+ * 0 if cpu_stop_work was queued successfully and @fn will be called.
+ * ENOENT if @fn(@arg) was not executed because @cpu was offline.
+ */
+int stop_one_cpu_async(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
+		       struct cpu_stop_work *work_buf,
+		       struct cpu_stop_done *done)
+{
+	cpu_stop_init_done(done, 1);
+
+	work_buf->done = done;
+	work_buf->fn = fn;
+	work_buf->arg = arg;
+
+	if (cpu_stop_queue_work(cpu, work_buf))
+		return 0;
+
+	work_buf->done = NULL;
+
+	return -ENOENT;
+}
+
+/**
+ * cpu_stop_work_wait - wait for a stop initiated by stop_one_cpu_async().
+ * @work_buf: pointer to cpu_stop_work structure
+ *
+ * CONTEXT:
+ * Might sleep.
+ */
+void cpu_stop_work_wait(struct cpu_stop_work *work_buf)
+{
+	struct cpu_stop_done *done = work_buf->done;
+
+	wait_for_completion(&done->completion);
+	work_buf->done = NULL;
+}
+
 static bool queue_stop_cpus_work(const struct cpumask *cpumask,
 				 cpu_stop_fn_t fn, void *arg,
 				 struct cpu_stop_done *done)