Sometimes, the kernel will boot too fast for rcu_tasks_verify_self_tests
to have all required grace periods.
Wait extra jiffies for rcu_tasks_verify_self_tests so as not to punish
people who make Linux boot faster.
Although 'wait extra jiffies' approach may slow down the Linux boot, but
the CONFIG_PROVE_RCU option is only enabled for experts and for test only.
I also considered temporarily reduce the gp_sleep and init_fract before
rcu_tasks_verify_self_tests, but we can only guess those values
from experience.
Reported-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Suggested-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Tested-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
Signed-off-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
---
kernel/rcu/tasks.h | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index bd9f2e24f5c7..b1be85da29ec 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1766,7 +1766,38 @@ static int rcu_tasks_verify_self_tests(void)
{
int ret = 0;
int i;
+ int delay = 0;
+
+ for (i = 0; i < ARRAY_SIZE(tests); i++) {
+ if (!tests[i].notrun) { // still hanging.
+ ret = -1;
+ }
+ }
+
+ if (!ret)
+ return ret;
+
+#ifdef CONFIG_TASKS_RCU
+ delay = rcu_tasks.gp_sleep;
+ if (delay < rcu_tasks.init_fract)
+ delay = rcu_tasks.init_fract;
+#endif
+
+#ifdef CONFIG_TASKS_RUDE_RCU
+ if (delay < rcu_tasks_rude.gp_sleep)
+ delay = rcu_tasks_rude.gp_sleep;
+#endif
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+ if (delay < rcu_tasks_trace.gp_sleep)
+ delay = rcu_tasks_trace.gp_sleep;
+ if (delay < rcu_tasks_trace.init_fract)
+ delay = rcu_tasks_trace.init_fract;
+#endif
+ pr_info("wait extra %d jiffies for rcu tasks self tests\n", 2*delay);
+ schedule_timeout_uninterruptible(2*delay);
+
+ ret = 0;
for (i = 0; i < ARRAY_SIZE(tests); i++) {
if (!tests[i].notrun) { // still hanging.
--
2.25.1
