rcu: Move RCU CPU stall-warning code out of update.c

The RCU CPU stall-warning code for normal grace periods is currently
scattered across three files, due to earlier Tiny RCU support for RCU
CPU stall warnings and for old Kconfig options that have long since
been retired.  Given that it is hard for the lead RCU maintainer to
find relevant stall-warning code, it would be good to consolidate it.
This commit starts this process by moving stall-warning code from
kernel/rcu/update.c to a new kernel/rcu/tree_stall.h file.

Note that the definitions of rcu_cpu_stall_suppress and
rcu_cpu_stall_timeout must remain in kernel/rcu/update.h to provide
compatibility for kernel boot parameter lists.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index acee72c0b24b59945000cf1617e37895181c4036..4b58c907b4b7f416c76c8f6ac718c406d978570d 100644 (file)
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -233,6 +233,7 @@ static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
 #ifdef CONFIG_RCU_STALL_COMMON
 
 extern int rcu_cpu_stall_suppress;
+extern int rcu_cpu_stall_timeout;
 int rcu_jiffies_till_stall_check(void);
 
 #define rcu_ftrace_dump_stall_suppress() \

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index acd6ccf56faf9ff090b43ea08458b3380f22cc3d..424d50ccf9e62bb21c1a6566804bc5376b3789cd 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3858,5 +3858,6 @@ void __init rcu_init(void)
        srcu_init();
 }
 
+#include "tree_stall.h"
 #include "tree_exp.h"
 #include "tree_plugin.h"

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
new file mode 100644 (file)
index 0000000..682189f
--- /dev/null
+++ b/kernel/rcu/tree_stall.h
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * RCU CPU stall warnings for normal RCU grace periods
+ *
+ * Copyright IBM Corporation, 2019
+ *
+ * Author: Paul E. McKenney <paulmck@linux.ibm.com>
+ */
+
+
+#ifdef CONFIG_PROVE_RCU
+#define RCU_STALL_DELAY_DELTA         (5 * HZ)
+#else
+#define RCU_STALL_DELAY_DELTA         0
+#endif
+
+int rcu_jiffies_till_stall_check(void)
+{
+       int till_stall_check = READ_ONCE(rcu_cpu_stall_timeout);
+
+       /*
+        * Limit check must be consistent with the Kconfig limits
+        * for CONFIG_RCU_CPU_STALL_TIMEOUT.
+        */
+       if (till_stall_check < 3) {
+               WRITE_ONCE(rcu_cpu_stall_timeout, 3);
+               till_stall_check = 3;
+       } else if (till_stall_check > 300) {
+               WRITE_ONCE(rcu_cpu_stall_timeout, 300);
+               till_stall_check = 300;
+       }
+       return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
+}
+EXPORT_SYMBOL_GPL(rcu_jiffies_till_stall_check);
+
+void rcu_sysrq_start(void)
+{
+       if (!rcu_cpu_stall_suppress)
+               rcu_cpu_stall_suppress = 2;
+}
+
+void rcu_sysrq_end(void)
+{
+       if (rcu_cpu_stall_suppress == 2)
+               rcu_cpu_stall_suppress = 0;
+}
+
+static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
+{
+       rcu_cpu_stall_suppress = 1;
+       return NOTIFY_DONE;
+}
+
+static struct notifier_block rcu_panic_block = {
+       .notifier_call = rcu_panic,
+};
+
+static int __init check_cpu_stall_init(void)
+{
+       atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
+       return 0;
+}
+early_initcall(check_cpu_stall_init);

diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index cbaa976c594518653bc3ef985361e812187e1ff2..c3bf44ba42e5420117601047fc7d1bdd7d511bad 100644 (file)
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -424,68 +424,11 @@ EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
 #endif
 
 #ifdef CONFIG_RCU_STALL_COMMON
-
-#ifdef CONFIG_PROVE_RCU
-#define RCU_STALL_DELAY_DELTA         (5 * HZ)
-#else
-#define RCU_STALL_DELAY_DELTA         0
-#endif
-
 int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
 EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress);
-static int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
-
 module_param(rcu_cpu_stall_suppress, int, 0644);
+int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
 module_param(rcu_cpu_stall_timeout, int, 0644);
-
-int rcu_jiffies_till_stall_check(void)
-{
-       int till_stall_check = READ_ONCE(rcu_cpu_stall_timeout);
-
-       /*
-        * Limit check must be consistent with the Kconfig limits
-        * for CONFIG_RCU_CPU_STALL_TIMEOUT.
-        */
-       if (till_stall_check < 3) {
-               WRITE_ONCE(rcu_cpu_stall_timeout, 3);
-               till_stall_check = 3;
-       } else if (till_stall_check > 300) {
-               WRITE_ONCE(rcu_cpu_stall_timeout, 300);
-               till_stall_check = 300;
-       }
-       return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
-}
-EXPORT_SYMBOL_GPL(rcu_jiffies_till_stall_check);
-
-void rcu_sysrq_start(void)
-{
-       if (!rcu_cpu_stall_suppress)
-               rcu_cpu_stall_suppress = 2;
-}
-
-void rcu_sysrq_end(void)
-{
-       if (rcu_cpu_stall_suppress == 2)
-               rcu_cpu_stall_suppress = 0;
-}
-
-static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
-{
-       rcu_cpu_stall_suppress = 1;
-       return NOTIFY_DONE;
-}
-
-static struct notifier_block rcu_panic_block = {
-       .notifier_call = rcu_panic,
-};
-
-static int __init check_cpu_stall_init(void)
-{
-       atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
-       return 0;
-}
-early_initcall(check_cpu_stall_init);
-
 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
 
 #ifdef CONFIG_TASKS_RCU