srcu: Initialize SRCU after timers

Once srcu_init() is called, the SRCU core will make use of delayed
workqueues, which rely on timers.  However init_timers() is called
several steps after rcu_init().  This means that a call_srcu() after
rcu_init() but before init_timers() would find itself within a dangerously
uninitialized timer core.

This commit therefore creates a separate call to srcu_init() after
init_timer() completes, which ensures that we stay in early SRCU mode
until timers are safe(r).

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index a0895bbf71ce01b7ea7a202a99c365dc609428ac..e6011a9975af2dff846922464c4821a410ddb0ec 100644 (file)
--- 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 eb01e121d2f15ca12f691277d5040eccf5c24476..7b6f49c4d38831495bb4a5eacf66113e457a897c 100644 (file)
--- 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>
@@ -979,6 +980,7 @@ 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 bf0827d4b6593a3b3337125d82acba87cca1ad15..ca3f2af32bf8907603e26ccc21215570d691de3f 100644 (file)
--- 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 f4f0cbf7a02bbe073ef0ffcb35a520aa579c9ba4..9ec35c15874003998cf49c605e478e01f3a64cb8 100644 (file)
--- 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 c8a029fbb114342469cb2c8f1a8d7ae857e0fad6..340b3f8b090d41e8ff128960c2fb2a6deeca6b43 100644 (file)
--- 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 8e78b2430c168f29054be180424dc9ea573019f4..c35b15229cff952d95d241fc9c14a05db2ab8635 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4735,7 +4735,6 @@ 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! */