[PATCH] rcu-tasks: Dump rcu tasks status when the boot-test failed

[Zqiang]

This commit adds a dump RCU task status function to rcu tasks tests,
used to obtain more information to help debug when the RCU tasks
boot-time tests failed.

Signed-off-by: Zqiang <qiang.zhang@xxxxxxxxx>
---

 syzbot reported the RCU tasks boot-time test failed:
 https://syzkaller.appspot.com/bug?extid=251e9abcdac140e7ec74

 kernel/rcu/tasks.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 7f7d1e636217..d9e1e53f4ccf 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1453,6 +1453,7 @@ struct rcu_tasks_test_desc {
 	const char *name;
 	bool notrun;
 	unsigned long runstart;
+	void (*gp_dbg)(void);
 };
 
 static struct rcu_tasks_test_desc tests[] = {
@@ -1460,6 +1461,8 @@ static struct rcu_tasks_test_desc tests[] = {
 		.name = "call_rcu_tasks()",
 		/* If not defined, the test is skipped. */
 		.notrun = IS_ENABLED(CONFIG_TASKS_RCU),
+		/* Dump rcu tasks status, if test failed. */
+		.gp_dbg = show_rcu_tasks_classic_gp_kthread
 	},
 	{
 		.name = "call_rcu_tasks_trace()",
@@ -1519,6 +1522,8 @@ static int rcu_tasks_verify_self_tests(void)
 		while (tests[i].notrun) {		// still hanging.
 			if (time_after(jiffies, tests[i].runstart + bst)) {
 				pr_err("%s has failed boot-time tests.\n", tests[i].name);
+				if (tests[i].gp_dbg)
+					tests[i].gp_dbg();
 				ret = -1;
 				break;
 			}
-- 
2.17.1