[PATCH 07/10] rcu: Separate the RCU synchronization types and APIs into

Ingo Molnar
2017-02-08T19:42:21Z

So rcupdate.h is a pretty complex header, in particular it includes
<linux/completion.h> which includes <linux/wait.h> - creating a
dependency that includes <linux/wait.h> in <linux/sched.h>,
which prevents the isolation of <linux/sched.h> from the derived
<linux/wait.h> header.

Solve part of the problem by decoupling rcupdate.h from completions:
this can be done by separating out the rcu_synchronize types and APIs,
and updating their usage sites.

Since this is a mostly RCU-internal types this will not just simplify
<linux/sched.h>'s dependencies, but will make all the hundreds of
.c files that include rcupdate.h but not completions or wait.h build
faster.

( For rcutiny this means that two dependent APIs have to be uninlined,
but that shouldn't be much of a problem as they are rare variants. )

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
fs/autofs4/autofs_i.h | 1 +
include/linux/dcache.h | 1 +
include/linux/rcupdate.h | 40 ----------------------------------------
include/linux/rcupdate_wait.h | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/rcutiny.h | 11 ++---------
kernel/rcu/srcu.c | 2 +-
kernel/rcu/tiny.c | 14 +++++++++++++-
kernel/rcu/tree.c | 2 +-
kernel/rcu/update.c | 1 +
kernel/sched/core.c | 1 +
10 files changed, 71 insertions(+), 52 deletions(-)

diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index c885daae68c8..beef981aa54f 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -14,6 +14,7 @@
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/list.h>
+#include <linux/completion.h>

/* This is the range of ioctl() numbers we claim as ours */
#define AUTOFS_IOC_FIRST AUTOFS_IOC_READY
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index c965e4469499..16948defb568 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -11,6 +11,7 @@
#include <linux/rcupdate.h>
#include <linux/lockref.h>
#include <linux/stringhash.h>
+#include <linux/wait.h>

struct path;
struct vfsmount;
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 01f71e1d2e94..1f476b63c596 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -40,7 +40,6 @@
#include <linux/cpumask.h>
#include <linux/seqlock.h>
#include <linux/lockdep.h>
-#include <linux/completion.h>
#include <linux/debugobjects.h>
#include <linux/bug.h>
#include <linux/compiler.h>
@@ -226,45 +225,6 @@ void call_rcu_sched(struct rcu_head *head,

void synchronize_sched(void);

-/*
- * Structure allowing asynchronous waiting on RCU.
- */
-struct rcu_synchronize {
- struct rcu_head head;
- struct completion completion;
-};
-void wakeme_after_rcu(struct rcu_head *head);
-
-void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
- struct rcu_synchronize *rs_array);
-
-#define _wait_rcu_gp(checktiny, ...) \
-do { \
- call_rcu_func_t __crcu_array[] = { __VA_ARGS__ }; \
- struct rcu_synchronize __rs_array[ARRAY_SIZE(__crcu_array)]; \
- __wait_rcu_gp(checktiny, ARRAY_SIZE(__crcu_array), \
- __crcu_array, __rs_array); \
-} while (0)
-
-#define wait_rcu_gp(...) _wait_rcu_gp(false, __VA_ARGS__)
-
-/**
- * synchronize_rcu_mult - Wait concurrently for multiple grace periods
- * @...: List of call_rcu() functions for the flavors to wait on.
- *
- * This macro waits concurrently for multiple flavors of RCU grace periods.
- * For example, synchronize_rcu_mult(call_rcu, call_rcu_bh) would wait
- * on concurrent RCU and RCU-bh grace periods. Waiting on a give SRCU
- * domain requires you to write a wrapper function for that SRCU domain's
- * call_srcu() function, supplying the corresponding srcu_struct.
- *
- * If Tiny RCU, tell _wait_rcu_gp() not to bother waiting for RCU
- * or RCU-bh, given that anywhere synchronize_rcu_mult() can be called
- * is automatically a grace period.
- */
-#define synchronize_rcu_mult(...) \
- _wait_rcu_gp(IS_ENABLED(CONFIG_TINY_RCU), __VA_ARGS__)
-
/**
* call_rcu_tasks() - Queue an RCU for invocation task-based grace period
* @head: structure to be used for queueing the RCU updates.
diff --git a/include/linux/rcupdate_wait.h b/include/linux/rcupdate_wait.h
new file mode 100644
index 000000000000..e774b4f5f220
--- /dev/null
+++ b/include/linux/rcupdate_wait.h
@@ -0,0 +1,50 @@
+#ifndef _LINUX_SCHED_RCUPDATE_WAIT_H
+#define _LINUX_SCHED_RCUPDATE_WAIT_H
+
+/*
+ * RCU synchronization types and methods:
+ */
+
+#include <linux/rcupdate.h>
+#include <linux/completion.h>
+
+/*
+ * Structure allowing asynchronous waiting on RCU.
+ */
+struct rcu_synchronize {
+ struct rcu_head head;
+ struct completion completion;
+};
+void wakeme_after_rcu(struct rcu_head *head);
+
+void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
+ struct rcu_synchronize *rs_array);
+
+#define _wait_rcu_gp(checktiny, ...) \
+do { \
+ call_rcu_func_t __crcu_array[] = { __VA_ARGS__ }; \
+ struct rcu_synchronize __rs_array[ARRAY_SIZE(__crcu_array)]; \
+ __wait_rcu_gp(checktiny, ARRAY_SIZE(__crcu_array), \
+ __crcu_array, __rs_array); \
+} while (0)
+
+#define wait_rcu_gp(...) _wait_rcu_gp(false, __VA_ARGS__)
+
+/**
+ * synchronize_rcu_mult - Wait concurrently for multiple grace periods
+ * @...: List of call_rcu() functions for the flavors to wait on.
+ *
+ * This macro waits concurrently for multiple flavors of RCU grace periods.
+ * For example, synchronize_rcu_mult(call_rcu, call_rcu_bh) would wait
+ * on concurrent RCU and RCU-bh grace periods. Waiting on a give SRCU
+ * domain requires you to write a wrapper function for that SRCU domain's
+ * call_srcu() function, supplying the corresponding srcu_struct.
+ *
+ * If Tiny RCU, tell _wait_rcu_gp() not to bother waiting for RCU
+ * or RCU-bh, given that anywhere synchronize_rcu_mult() can be called
+ * is automatically a grace period.
+ */
+#define synchronize_rcu_mult(...) \
+ _wait_rcu_gp(IS_ENABLED(CONFIG_TINY_RCU), __VA_ARGS__)
+
+#endif /* _LINUX_SCHED_RCUPDATE_WAIT_H */
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index ac81e4063b40..861ab86ae302 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -47,15 +47,8 @@ static inline void cond_synchronize_sched(unsigned long oldstate)
might_sleep();
}

-static inline void rcu_barrier_bh(void)
-{
- wait_rcu_gp(call_rcu_bh);
-}
-
-static inline void rcu_barrier_sched(void)
-{
- wait_rcu_gp(call_rcu_sched);
-}
+extern void rcu_barrier_bh(void);
+extern void rcu_barrier_sched(void);

static inline void synchronize_rcu_expedited(void)
{
diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
index 9b9cdd549caa..c05855490b54 100644
--- a/kernel/rcu/srcu.c
+++ b/kernel/rcu/srcu.c
@@ -30,7 +30,7 @@
#include <linux/mutex.h>
#include <linux/percpu.h>
#include <linux/preempt.h>
-#include <linux/rcupdate.h>
+#include <linux/rcupdate_wait.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/delay.h>
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index b23a4d076f3d..55770f10342e 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -25,7 +25,7 @@
#include <linux/completion.h>
#include <linux/interrupt.h>
#include <linux/notifier.h>
-#include <linux/rcupdate.h>
+#include <linux/rcupdate_wait.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/mutex.h>
@@ -49,6 +49,18 @@ static void __call_rcu(struct rcu_head *head,

#include "tiny_plugin.h"

+void rcu_barrier_bh(void)
+{
+ wait_rcu_gp(call_rcu_bh);
+}
+EXPORT_SYMBOL(rcu_barrier_bh);
+
+void rcu_barrier_sched(void)
+{
+ wait_rcu_gp(call_rcu_sched);
+}
+EXPORT_SYMBOL(rcu_barrier_sched);
+
#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE)

/*
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index cb4e2056ccf3..2d87cb3ad7c6 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -32,7 +32,7 @@
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
-#include <linux/rcupdate.h>
+#include <linux/rcupdate_wait.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/nmi.h>
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 4f6db7e6a117..2730e5c9ad2e 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -49,6 +49,7 @@
#include <linux/moduleparam.h>
#include <linux/kthread.h>
#include <linux/tick.h>
+#include <linux/rcupdate_wait.h>

#define CREATE_TRACE_POINTS

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 258af6d00682..f3ce7cf60002 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10,6 +10,7 @@
#include <linux/delayacct.h>
#include <linux/init_task.h>
#include <linux/context_tracking.h>
+#include <linux/rcupdate_wait.h>

#include <linux/blkdev.h>
#include <linux/kprobes.h>
--
2.7.4