[PATCH rcu 1/2] torture: Add a kthread-creation callback to _torture_create_kthread()

["Paul E. McKenney" <paulmck@xxxxxxxxxx>]

This commit adds a kthread-creation callback to the
_torture_create_kthread() function, which allows callers of a new
torture_create_kthread_cb() macro to specify a function to be invoked
after the kthread is created but before it is awakened for the first time.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: John Stultz <jstultz@xxxxxxxxxx>
Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: kernel-team@xxxxxxxxxxx
---
 include/linux/torture.h | 7 +++++--
 kernel/torture.c        | 6 +++++-
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/include/linux/torture.h b/include/linux/torture.h
index 7038104463e4..bb466eec01e4 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -108,12 +108,15 @@ bool torture_must_stop(void);
 bool torture_must_stop_irq(void);
 void torture_kthread_stopping(char *title);
 int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
-			     char *f, struct task_struct **tp);
+			     char *f, struct task_struct **tp, void (*cbf)(struct task_struct *tp));
 void _torture_stop_kthread(char *m, struct task_struct **tp);
 
 #define torture_create_kthread(n, arg, tp) \
 	_torture_create_kthread(n, (arg), #n, "Creating " #n " task", \
-				"Failed to create " #n, &(tp))
+				"Failed to create " #n, &(tp), NULL)
+#define torture_create_kthread_cb(n, arg, tp, cbf) \
+	_torture_create_kthread(n, (arg), #n, "Creating " #n " task", \
+				"Failed to create " #n, &(tp), cbf)
 #define torture_stop_kthread(n, tp) \
 	_torture_stop_kthread("Stopping " #n " task", &(tp))
 
diff --git a/kernel/torture.c b/kernel/torture.c
index 8be83fdc6be1..b88a1a86d9da 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -932,7 +932,7 @@ EXPORT_SYMBOL_GPL(torture_kthread_stopping);
  * it starts, you will need to open-code your own.
  */
 int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
-			    char *f, struct task_struct **tp)
+			    char *f, struct task_struct **tp, void (*cbf)(struct task_struct *tp))
 {
 	int ret = 0;
 
@@ -944,6 +944,10 @@ int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
 		*tp = NULL;
 		return ret;
 	}
+
+	if (cbf)
+		cbf(*tp);
+
 	wake_up_process(*tp);  // Process is sleeping, so ordering provided.
 	torture_shuffle_task_register(*tp);
 	return ret;
-- 
2.40.1