[PATCH] rcu: make PREEMPT_RCU to be a decoration of TREE_RCU

* [PATCH] rcu: make PREEMPT_RCU to be a decoration of TREE_RCU
@ 2019-10-13 12:59 Lai Jiangshan
  2019-10-14 18:48 ` Joel Fernandes
  0 siblings, 1 reply; 10+ messages in thread
From: Lai Jiangshan @ 2019-10-13 12:59 UTC (permalink / raw)
  Cc: Lai Jiangshan, Lai Jiangshan, Paul E. McKenney, Josh Triplett,
	Steven Rostedt, Mathieu Desnoyers, Joel Fernandes, Ingo Molnar,
	Luis Chamberlain, Kees Cook, David Sterba, Yafang Shao,
	Mike Rapoport, Petr Mladek, Sakari Ailus, rcu, linux-kernel,
	linux-fsdevel

Currently PREEMPT_RCU and TREE_RCU are "contrary" configs
when they can't be both on. But PREEMPT_RCU is actually a kind
of TREE_RCU in the implementation. It seams to be appropriate
to make PREEMPT_RCU to be a decorative option of TREE_RCU.

Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
 include/linux/rcupdate.h   |  4 ++--
 include/trace/events/rcu.h |  4 ++--
 kernel/rcu/Kconfig         | 13 +++++++------
 kernel/rcu/Makefile        |  1 -
 kernel/rcu/rcu.h           |  2 +-
 kernel/rcu/update.c        |  2 +-
 kernel/sysctl.c            |  2 +-
 7 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 75a2eded7aa2..1eee9f6c27f9 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -167,7 +167,7 @@ do { \
  * TREE_RCU and rcu_barrier_() primitives in TINY_RCU.
  */
 
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
+#if defined(CONFIG_TREE_RCU)
 #include <linux/rcutree.h>
 #elif defined(CONFIG_TINY_RCU)
 #include <linux/rcutiny.h>
@@ -583,7 +583,7 @@ do {									      \
  * read-side critical section that would block in a !PREEMPT kernel.
  * But if you want the full story, read on!
  *
- * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU),
+ * In non-preemptible RCU implementations (pure TREE_RCU and TINY_RCU),
  * it is illegal to block while in an RCU read-side critical section.
  * In preemptible RCU implementations (PREEMPT_RCU) in CONFIG_PREEMPTION
  * kernel builds, RCU read-side critical sections may be preempted,
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 694bd040cf51..1ce15c5be4c8 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -41,7 +41,7 @@ TRACE_EVENT(rcu_utilization,
 	TP_printk("%s", __entry->s)
 );
 
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
+#if defined(CONFIG_TREE_RCU)
 
 /*
  * Tracepoint for grace-period events.  Takes a string identifying the
@@ -425,7 +425,7 @@ TRACE_EVENT_RCU(rcu_fqs,
 		  __entry->cpu, __entry->qsevent)
 );
 
-#endif /* #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) */
+#endif /* #if defined(CONFIG_TREE_RCU) */
 
 /*
  * Tracepoint for dyntick-idle entry/exit events.  These take a string
diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index 7644eda17d62..0303934e6ef0 100644
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -7,7 +7,7 @@ menu "RCU Subsystem"
 
 config TREE_RCU
 	bool
-	default y if !PREEMPTION && SMP
+	default y if SMP
 	help
 	  This option selects the RCU implementation that is
 	  designed for very large SMP system with hundreds or
@@ -17,6 +17,7 @@ config TREE_RCU
 config PREEMPT_RCU
 	bool
 	default y if PREEMPTION
+	select TREE_RCU
 	help
 	  This option selects the RCU implementation that is
 	  designed for very large SMP systems with hundreds or
@@ -78,7 +79,7 @@ config TASKS_RCU
 	  user-mode execution as quiescent states.
 
 config RCU_STALL_COMMON
-	def_bool ( TREE_RCU || PREEMPT_RCU )
+	def_bool TREE_RCU
 	help
 	  This option enables RCU CPU stall code that is common between
 	  the TINY and TREE variants of RCU.  The purpose is to allow
@@ -86,13 +87,13 @@ config RCU_STALL_COMMON
 	  making these warnings mandatory for the tree variants.
 
 config RCU_NEED_SEGCBLIST
-	def_bool ( TREE_RCU || PREEMPT_RCU || TREE_SRCU )
+	def_bool ( TREE_RCU || TREE_SRCU )
 
 config RCU_FANOUT
 	int "Tree-based hierarchical RCU fanout value"
 	range 2 64 if 64BIT
 	range 2 32 if !64BIT
-	depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
+	depends on TREE_RCU && RCU_EXPERT
 	default 64 if 64BIT
 	default 32 if !64BIT
 	help
@@ -112,7 +113,7 @@ config RCU_FANOUT_LEAF
 	int "Tree-based hierarchical RCU leaf-level fanout value"
 	range 2 64 if 64BIT
 	range 2 32 if !64BIT
-	depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
+	depends on TREE_RCU && RCU_EXPERT
 	default 16
 	help
 	  This option controls the leaf-level fanout of hierarchical
@@ -187,7 +188,7 @@ config RCU_BOOST_DELAY
 
 config RCU_NOCB_CPU
 	bool "Offload RCU callback processing from boot-selected CPUs"
-	depends on TREE_RCU || PREEMPT_RCU
+	depends on TREE_RCU
 	depends on RCU_EXPERT || NO_HZ_FULL
 	default n
 	help
diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile
index 020e8b6a644b..82d5fba48b2f 100644
--- a/kernel/rcu/Makefile
+++ b/kernel/rcu/Makefile
@@ -9,6 +9,5 @@ obj-$(CONFIG_TINY_SRCU) += srcutiny.o
 obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
 obj-$(CONFIG_RCU_PERF_TEST) += rcuperf.o
 obj-$(CONFIG_TREE_RCU) += tree.o
-obj-$(CONFIG_PREEMPT_RCU) += tree.o
 obj-$(CONFIG_TINY_RCU) += tiny.o
 obj-$(CONFIG_RCU_NEED_SEGCBLIST) += rcu_segcblist.o
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 8fd4f82c9b3d..4149ba76824f 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -452,7 +452,7 @@ enum rcutorture_type {
 	INVALID_RCU_FLAVOR
 };
 
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
+#if defined(CONFIG_TREE_RCU)
 void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
 			    unsigned long *gp_seq);
 void rcutorture_record_progress(unsigned long vernum);
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 1861103662db..34a7452b25fd 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -435,7 +435,7 @@ struct debug_obj_descr rcuhead_debug_descr = {
 EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
 
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
+#if defined(CONFIG_TREE_RCU) || defined(CONFIG_RCU_TRACE)
 void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp,
 			       unsigned long secs,
 			       unsigned long c_old, unsigned long c)
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 00fcea236eba..2ace158a4d72 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1268,7 +1268,7 @@ static struct ctl_table kern_table[] = {
 		.proc_handler	= proc_do_static_key,
 	},
 #endif
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
+#if defined(CONFIG_TREE_RCU)
 	{
 		.procname	= "panic_on_rcu_stall",
 		.data		= &sysctl_panic_on_rcu_stall,
-- 
2.20.1


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