The following commit has been merged into the core/rcu branch of tip: Commit-ID: 8e9c01c717df7e05c5bd1ca86aaa3a74b31f37f1 Gitweb: https://git.kernel.org/tip/8e9c01c717df7e05c5bd1ca86aaa3a74b31f37f1 Author: Frederic Weisbecker <frederic@xxxxxxxxxx> AuthorDate: Fri, 09 Apr 2021 00:38:59 +02:00 Committer: Paul E. McKenney <paulmck@xxxxxxxxxx> CommitterDate: Mon, 10 May 2021 16:03:35 -07:00 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@xxxxxxxxxx> Cc: Uladzislau Rezki <urezki@xxxxxxxxx> Cc: Boqun Feng <boqun.feng@xxxxxxxxx> Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx> Cc: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx> Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx> Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> --- 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 a0895bb..e6011a9 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 eb01e12..7b6f49c 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> @@ -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 bf0827d..ca3f2af 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 f4f0cbf..9ec35c1 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 c8a029f..340b3f8 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 8e78b24..c35b152 100644 --- 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! */
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