Once srcu_init() is called, the SRCU core is free to queue delayed
workqueues, which rely on timers. However init_timers() is called
several steps after rcu_init(). Any call_srcu() in-between would finish
its course inside a dangerously uninitialized timer core.
Make sure we stay in early SRCU mode until everything is well settled.
Signed-off-by: Frederic Weisbecker <frede...@kernel.org>
Cc: Uladzislau Rezki <ure...@gmail.com>
Cc: Boqun Feng <boqun.f...@gmail.com>
Cc: Lai Jiangshan <jiangshan...@gmail.com>
Cc: Neeraj Upadhyay <neer...@codeaurora.org>
Cc: Josh Triplett <j...@joshtriplett.org>
Cc: Joel Fernandes <j...@joelfernandes.org>
---
include/linux/srcu.h | 6 ++++++
init/main.c | 2 ++
kernel/rcu/rcu.h | 6 ------
kernel/rcu/srcutree.c | 5 +++++
kernel/rcu/tiny.c | 1 -
kernel/rcu/tree.c | 1 -
6 files changed, 13 insertions(+), 8 deletions(-)
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index a0895bbf71ce..e6011a9975af 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -64,6 +64,12 @@ unsigned long get_state_synchronize_srcu(struct srcu_struct
*ssp);
unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp);
bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long
cookie);
+#ifdef CONFIG_SRCU
+void srcu_init(void);
+#else /* #ifdef CONFIG_SRCU */
+static inline void srcu_init(void) { }
+#endif /* #else #ifdef CONFIG_SRCU */
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
/**
diff --git a/init/main.c b/init/main.c
index 53b278845b88..1bc5cc9e52ef 100644
--- a/init/main.c
+++ b/init/main.c
@@ -42,6 +42,7 @@
#include <linux/profile.h>
#include <linux/kfence.h>
#include <linux/rcupdate.h>
+#include <linux/srcu.h>
#include <linux/moduleparam.h>
#include <linux/kallsyms.h>
#include <linux/writeback.h>
@@ -956,6 +957,7 @@ asmlinkage __visible void __init __no_sanitize_address
start_kernel(void)
tick_init();
rcu_init_nohz();
init_timers();
+ srcu_init();
hrtimers_init();
softirq_init();
timekeeping_init();
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index d64b842f4078..b3af34068051 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -422,12 +422,6 @@ do {
\
#endif /* #if defined(CONFIG_SRCU) || !defined(CONFIG_TINY_RCU) */
-#ifdef CONFIG_SRCU
-void srcu_init(void);
-#else /* #ifdef CONFIG_SRCU */
-static inline void srcu_init(void) { }
-#endif /* #else #ifdef CONFIG_SRCU */
-
#ifdef CONFIG_TINY_RCU
/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
static inline bool rcu_gp_is_normal(void) { return true; }
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 10e681ea7051..108f9ca06047 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1384,6 +1384,11 @@ void __init srcu_init(void)
{
struct srcu_struct *ssp;
+ /*
+ * Once that is set, call_srcu() can follow the normal path and
+ * queue delayed work. This must follow RCU workqueues creation
+ * and timers initialization.
+ */
srcu_init_done = true;
while (!list_empty(&srcu_boot_list)) {
ssp = list_first_entry(&srcu_boot_list, struct srcu_struct,
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index c8a029fbb114..340b3f8b090d 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -221,5 +221,4 @@ void __init rcu_init(void)
{
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
rcu_early_boot_tests();
- srcu_init();
}
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 5c214705c33f..740f5cd34459 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4714,7 +4714,6 @@ void __init rcu_init(void)
WARN_ON(!rcu_gp_wq);
rcu_par_gp_wq = alloc_workqueue("rcu_par_gp", WQ_MEM_RECLAIM, 0);
WARN_ON(!rcu_par_gp_wq);
- srcu_init();
/* Fill in default value for rcutree.qovld boot parameter. */
/* -After- the rcu_node ->lock fields are initialized! */
--
2.25.1
