diff mbox series

[rcu,01/17] srcu: Make Tiny SRCU able to operate in preemptible kernels

Message ID 20250116202112.3783327-1-paulmck@kernel.org (mailing list archive)
State New
Headers show
Series SRCU updates, including SRCU-fast | expand

Commit Message

Paul E. McKenney Jan. 16, 2025, 8:20 p.m. UTC 
Given that SRCU allows its read-side critical sections are not just
preemptible, but also allow general blocking, there is not much
reason to restrict Tiny SRCU to non-preemptible kernels.  This commit
therefore removes Tiny SRCU dependencies on non-preemptibility, primarily
surrounding its interaction with rcutorture and early boot.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Ankur Arora <ankur.a.arora@oracle.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: <bpf@vger.kernel.org>
---
 kernel/rcu/rcu.h      | 9 ++++++---
 kernel/rcu/srcutiny.c | 6 ++++++
 2 files changed, 12 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index f87c9d6d36fcb..f6fcf87d91395 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -611,8 +611,6 @@  void srcutorture_get_gp_data(struct srcu_struct *sp, int *flags,
 static inline bool rcu_watching_zero_in_eqs(int cpu, int *vp) { return false; }
 static inline unsigned long rcu_get_gp_seq(void) { return 0; }
 static inline unsigned long rcu_exp_batches_completed(void) { return 0; }
-static inline unsigned long
-srcu_batches_completed(struct srcu_struct *sp) { return 0; }
 static inline void rcu_force_quiescent_state(void) { }
 static inline bool rcu_check_boost_fail(unsigned long gp_state, int *cpup) { return true; }
 static inline void show_rcu_gp_kthreads(void) { }
@@ -624,7 +622,6 @@  static inline void rcu_gp_slow_unregister(atomic_t *rgssp) { }
 bool rcu_watching_zero_in_eqs(int cpu, int *vp);
 unsigned long rcu_get_gp_seq(void);
 unsigned long rcu_exp_batches_completed(void);
-unsigned long srcu_batches_completed(struct srcu_struct *sp);
 bool rcu_check_boost_fail(unsigned long gp_state, int *cpup);
 void show_rcu_gp_kthreads(void);
 int rcu_get_gp_kthreads_prio(void);
@@ -636,6 +633,12 @@  void rcu_gp_slow_register(atomic_t *rgssp);
 void rcu_gp_slow_unregister(atomic_t *rgssp);
 #endif /* #else #ifdef CONFIG_TINY_RCU */
 
+#ifdef CONFIG_TINY_SRCU
+static inline unsigned long srcu_batches_completed(struct srcu_struct *sp) { return 0; }
+#else // #ifdef CONFIG_TINY_SRCU
+unsigned long srcu_batches_completed(struct srcu_struct *sp);
+#endif // #else // #ifdef CONFIG_TINY_SRCU
+
 #ifdef CONFIG_RCU_NOCB_CPU
 void rcu_bind_current_to_nocb(void);
 #else
diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
index f688bdad293ed..6e9fe2ce1075d 100644
--- a/kernel/rcu/srcutiny.c
+++ b/kernel/rcu/srcutiny.c
@@ -20,7 +20,11 @@ 
 #include "rcu_segcblist.h"
 #include "rcu.h"
 
+#ifndef CONFIG_TREE_RCU
 int rcu_scheduler_active __read_mostly;
+#else // #ifndef CONFIG_TREE_RCU
+extern int rcu_scheduler_active;
+#endif // #else // #ifndef CONFIG_TREE_RCU
 static LIST_HEAD(srcu_boot_list);
 static bool srcu_init_done;
 
@@ -282,11 +286,13 @@  bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie)
 }
 EXPORT_SYMBOL_GPL(poll_state_synchronize_srcu);
 
+#ifndef CONFIG_TREE_RCU
 /* Lockdep diagnostics.  */
 void __init rcu_scheduler_starting(void)
 {
 	rcu_scheduler_active = RCU_SCHEDULER_RUNNING;
 }
+#endif // #ifndef CONFIG_TREE_RCU
 
 /*
  * Queue work for srcu_struct structures with early boot callbacks.