[PATCH tip/core/rcu 0/6] rcu: Tiny RCU, expedited RCU, rcutorture fixes, lockdep simplification

[PATCH tip/core/rcu 0/6] rcu: Tiny RCU, expedited RCU, rcutorture fixes, lockdep simplification

[Paul E. McKenney]

Updated patches for post 2.6.32:

o	RCU the Bloatwatch Edition, v8

o	Add synchronize_rcu_expedited().

o	Add rcutorture tests for synchronize_rcu_expedited().

o	Update RCU documentation for synchronize_rcu_expedited().

o	Make rcutorture list the torture types it knows about when
	complaining about the one specified.

o	Simplify creation of the separate lockdep class for the
	root rcu_node structure's lock.


 b/Documentation/RCU/whatisRCU.txt |    3 
 b/include/linux/hardirq.h         |   24 +++
 b/include/linux/rcupdate.h        |    6 
 b/include/linux/rcutiny.h         |   97 ++++++++++++
 b/include/linux/srcu.h            |    1 
 b/init/Kconfig                    |    9 +
 b/kernel/Makefile                 |    1 
 b/kernel/rcupdate.c               |    4 
 b/kernel/rcutiny.c                |  295 +++++++++++++++++++++++++++++++++++++-
 b/kernel/rcutorture.c             |   26 ++-
 b/kernel/rcutree.c                |    5 
 b/kernel/rcutree.h                |    3 
 b/kernel/srcu.c                   |   75 ++++++---
 kernel/rcutorture.c               |    7 
 14 files changed, 519 insertions(+), 37 deletions(-)

[PATCH tip/core/rcu 1/6] rcu: The Bloatwatch Edition, v8

[Paul E. McKenney]

This patch is a version of RCU designed for !SMP provided for a
small-footprint RCU implementation.  In particular, the implementation
of synchronize_rcu() is extremely lightweight and high performance.
It passes rcutorture testing in each of the four relevant configurations
(combinations of NO_HZ and PREEMPT) on x86.  This saves about 1K bytes
compared to old Classic RCU (which is no longer in mainline), and more
than three kilobytes compared to Hierarchical RCU (updated to 2.6.30):

	CONFIG_TREE_RCU:

	   text	   data	    bss	    dec	    filename
	    183       4       0     187     kernel/rcupdate.o
	   2783     520      36    3339     kernel/rcutree.o
				   3526 Total (vs 4565 for v7)

	CONFIG_TREE_PREEMPT_RCU:

	   text	   data	    bss	    dec	    filename
	    263       4       0     267     kernel/rcupdate.o
	   4594     776      52    5422     kernel/rcutree.o
	   			   5689 Total (6155 for v7)

	CONFIG_TINY_RCU:

	   text	   data	    bss	    dec	    filename
	     96       4       0     100     kernel/rcupdate.o
	    734      24       0     758     kernel/rcutiny.o
	    			    858 Total (vs 848 for v7)

The above is for x86.  Your mileage may vary on other platforms.
Further compression is possible, but is being procrastinated.

Changes from v7 (http://lkml.org/lkml/2009/10/9/388)

o	Apply Lai Jiangshan's review comments (aside from might_sleep()
	in synchronize_sched(), which is covered by SMP builds).

o	Fix up expedited primitives.

Changes from v6 (http://lkml.org/lkml/2009/9/23/293).

o	Forward ported to put it into the 2.6.33 stream.

o	Added lockdep support.

o	Make lightweight rcu_barrier.

Changes from v5 (http://lkml.org/lkml/2009/6/23/12).

o	Ported to latest pre-2.6.32 merge window kernel.

	- Renamed rcu_qsctr_inc() to rcu_sched_qs().
	- Renamed rcu_bh_qsctr_inc() to rcu_bh_qs().
	- Provided trivial rcu_cpu_notify().
	- Provided trivial exit_rcu().
	- Provided trivial rcu_needs_cpu().
	- Fixed up the rcu_*_enter/exit() functions in linux/hardirq.h.

o	Removed the dependence on EMBEDDED, with a view to making
	TINY_RCU default for !SMP at some time in the future.

o	Added (trivial) support for expedited grace periods.

Changes from v4 (http://lkml.org/lkml/2009/5/2/91) include:

o	Squeeze the size down a bit further by removing the
	->completed field from struct rcu_ctrlblk.

o	This permits synchronize_rcu() to become the empty function.
	Previous concerns about rcutorture were unfounded, as
	rcutorture correctly handles a constant value from
	rcu_batches_completed() and rcu_batches_completed_bh().

Changes from v3 (http://lkml.org/lkml/2009/3/29/221) include:

o	Changed rcu_batches_completed(), rcu_batches_completed_bh()
	rcu_enter_nohz(), rcu_exit_nohz(), rcu_nmi_enter(), and
	rcu_nmi_exit(), to be static inlines, as suggested by David
	Howells.  Doing this saves about 100 bytes from rcutiny.o.
	(The numbers between v3 and this v4 of the patch are not directly
	comparable, since they are against different versions of Linux.)

Changes from v2 (http://lkml.org/lkml/2009/2/3/333) include:

o	Fix whitespace issues.

o	Change short-circuit "||" operator to instead be "+" in order to
	fix performance bug noted by "kraai" on LWN.

		(http://lwn.net/Articles/324348/)

Changes from v1 (http://lkml.org/lkml/2009/1/13/440) include:

o	This version depends on EMBEDDED as well as !SMP, as suggested
	by Ingo.

o	Updated rcu_needs_cpu() to unconditionally return zero,
	permitting the CPU to enter dynticks-idle mode at any time.
	This works because callbacks can be invoked upon entry to
	dynticks-idle mode.

o	Paul is now OK with this being included, based on a poll at the
	Kernel Miniconf at linux.conf.au, where about ten people said
	that they cared about saving 900 bytes on single-CPU systems.

o	Applies to both mainline and tip/core/rcu.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 include/linux/hardirq.h  |   24 ++++
 include/linux/rcupdate.h |    6 +
 include/linux/rcutiny.h  |   97 +++++++++++++++
 init/Kconfig             |    9 ++
 kernel/Makefile          |    1 +
 kernel/rcupdate.c        |    4 +
 kernel/rcutiny.c         |  294 ++++++++++++++++++++++++++++++++++++++++++++++
 7 files changed, 435 insertions(+), 0 deletions(-)
 create mode 100644 include/linux/rcutiny.h
 create mode 100644 kernel/rcutiny.c

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 6d527ee..d5b3876 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -139,10 +139,34 @@ static inline void account_system_vtime(struct task_struct *tsk)
 #endif
 
 #if defined(CONFIG_NO_HZ)
+#if defined(CONFIG_TINY_RCU)
+extern void rcu_enter_nohz(void);
+extern void rcu_exit_nohz(void);
+
+static inline void rcu_irq_enter(void)
+{
+	rcu_exit_nohz();
+}
+
+static inline void rcu_irq_exit(void)
+{
+	rcu_enter_nohz();
+}
+
+static inline void rcu_nmi_enter(void)
+{
+}
+
+static inline void rcu_nmi_exit(void)
+{
+}
+
+#else
 extern void rcu_irq_enter(void);
 extern void rcu_irq_exit(void);
 extern void rcu_nmi_enter(void);
 extern void rcu_nmi_exit(void);
+#endif
 #else
 # define rcu_irq_enter() do { } while (0)
 # define rcu_irq_exit() do { } while (0)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 3ebd0b7..6dd71fa 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -68,11 +68,17 @@ extern int sched_expedited_torture_stats(char *page);
 /* Internal to kernel */
 extern void rcu_init(void);
 extern void rcu_scheduler_starting(void);
+#ifndef CONFIG_TINY_RCU
 extern int rcu_needs_cpu(int cpu);
+#else
+static inline int rcu_needs_cpu(int cpu) { return 0; }
+#endif
 extern int rcu_scheduler_active;
 
 #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
 #include <linux/rcutree.h>
+#elif CONFIG_TINY_RCU
+#include <linux/rcutiny.h>
 #else
 #error "Unknown RCU implementation specified to kernel configuration"
 #endif
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
new file mode 100644
index 0000000..891073c
--- /dev/null
+++ b/include/linux/rcutiny.h
@@ -0,0 +1,97 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright IBM Corporation, 2008
+ *
+ * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * 		Documentation/RCU
+ */
+
+#ifndef __LINUX_TINY_H
+#define __LINUX_TINY_H
+
+#include <linux/cache.h>
+
+void rcu_sched_qs(int cpu);
+void rcu_bh_qs(int cpu);
+
+#define __rcu_read_lock()	preempt_disable()
+#define __rcu_read_unlock()	preempt_enable()
+#define __rcu_read_lock_bh()	local_bh_disable()
+#define __rcu_read_unlock_bh()	local_bh_enable()
+#define call_rcu_sched		call_rcu
+
+#define rcu_init_sched()	do { } while (0)
+extern void rcu_check_callbacks(int cpu, int user);
+extern void __rcu_init(void);
+
+/*
+ * Return the number of grace periods.
+ */
+static inline long rcu_batches_completed(void)
+{
+	return 0;
+}
+
+/*
+ * Return the number of bottom-half grace periods.
+ */
+static inline long rcu_batches_completed_bh(void)
+{
+	return 0;
+}
+
+extern int rcu_expedited_torture_stats(char *page);
+
+static inline void synchronize_rcu_expedited(void)
+{
+	synchronize_sched();
+}
+
+static inline void synchronize_rcu_bh_expedited(void)
+{
+	synchronize_sched();
+}
+
+struct notifier_block;
+extern int rcu_cpu_notify(struct notifier_block *self,
+			  unsigned long action, void *hcpu);
+
+#ifdef CONFIG_NO_HZ
+
+extern void rcu_enter_nohz(void);
+extern void rcu_exit_nohz(void);
+
+#else /* #ifdef CONFIG_NO_HZ */
+
+static inline void rcu_enter_nohz(void)
+{
+}
+
+static inline void rcu_exit_nohz(void)
+{
+}
+
+#endif /* #else #ifdef CONFIG_NO_HZ */
+
+static inline void exit_rcu(void)
+{
+}
+
+#endif /* __LINUX_RCUTINY_H */
diff --git a/init/Kconfig b/init/Kconfig
index 09c5c64..d367bf6 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -334,6 +334,15 @@ config TREE_PREEMPT_RCU
 	  is also required.  It also scales down nicely to
 	  smaller systems.
 
+config TINY_RCU
+	bool "UP-only small-memory-footprint RCU"
+	depends on !SMP
+	help
+	  This option selects the RCU implementation that is
+	  designed for UP systems from which real-time response
+	  is not required.  This option greatly reduces the
+	  memory footprint of RCU.
+
 endchoice
 
 config RCU_TRACE
diff --git a/kernel/Makefile b/kernel/Makefile
index b8d4cd8..e9a0e6e 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -82,6 +82,7 @@ obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
 obj-$(CONFIG_TREE_RCU) += rcutree.o
 obj-$(CONFIG_TREE_PREEMPT_RCU) += rcutree.o
 obj-$(CONFIG_TREE_RCU_TRACE) += rcutree_trace.o
+obj-$(CONFIG_TINY_RCU) += rcutiny.o
 obj-$(CONFIG_RELAY) += relay.o
 obj-$(CONFIG_SYSCTL) += utsname_sysctl.o
 obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 4001833..7625f20 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -67,6 +67,8 @@ void wakeme_after_rcu(struct rcu_head  *head)
 	complete(&rcu->completion);
 }
 
+#ifndef CONFIG_TINY_RCU
+
 #ifdef CONFIG_TREE_PREEMPT_RCU
 
 /**
@@ -157,6 +159,8 @@ void synchronize_rcu_bh(void)
 }
 EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
 
+#endif /* #ifndef CONFIG_TINY_RCU */
+
 static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,
 		unsigned long action, void *hcpu)
 {
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
new file mode 100644
index 0000000..0b54efd
--- /dev/null
+++ b/kernel/rcutiny.c
@@ -0,0 +1,294 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright IBM Corporation, 2008
+ *
+ * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * 		Documentation/RCU
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/notifier.h>
+#include <linux/cpu.h>
+#include <linux/mutex.h>
+#include <linux/time.h>
+
+/* Global control variables for rcupdate callback mechanism. */
+struct rcu_ctrlblk {
+	struct rcu_head *rcucblist;	/* List of pending callbacks (CBs). */
+	struct rcu_head **donetail;	/* ->next pointer of last "done" CB. */
+	struct rcu_head **curtail;	/* ->next pointer of last CB. */
+};
+
+/* Definition for rcupdate control block. */
+static struct rcu_ctrlblk rcu_ctrlblk = {
+	.rcucblist = NULL,
+	.donetail = &rcu_ctrlblk.rcucblist,
+	.curtail = &rcu_ctrlblk.rcucblist,
+};
+static struct rcu_ctrlblk rcu_bh_ctrlblk = {
+	.rcucblist = NULL,
+	.donetail = &rcu_bh_ctrlblk.rcucblist,
+	.curtail = &rcu_bh_ctrlblk.rcucblist,
+};
+
+#ifdef CONFIG_NO_HZ
+
+static long rcu_dynticks_nesting = 1;
+
+/*
+ * Enter dynticks-idle mode, which is an extended quiescent state
+ * if we have fully entered that mode (i.e., if the new value of
+ * dynticks_nesting is zero).
+ */
+void rcu_enter_nohz(void)
+{
+	if (--rcu_dynticks_nesting == 0)
+		rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
+}
+
+/*
+ * Exit dynticks-idle mode, so that we are no longer in an extended
+ * quiescent state.
+ */
+void rcu_exit_nohz(void)
+{
+	rcu_dynticks_nesting++;
+}
+
+#endif /* #ifdef CONFIG_NO_HZ */
+
+/*
+ * Helper function for rcu_qsctr_inc() and rcu_bh_qsctr_inc().
+ * Also disable irqs to avoid confusion due to interrupt handlers invoking
+ * call_rcu().
+ */
+static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	if (rcp->rcucblist != NULL &&
+	    rcp->donetail != rcp->curtail) {
+		rcp->donetail = rcp->curtail;
+		local_irq_restore(flags);
+		return 1;
+	}
+	local_irq_restore(flags);
+	return 0;
+}
+
+/*
+ * Record an rcu quiescent state.  And an rcu_bh quiescent state while we
+ * are at it, given that any rcu quiescent state is also an rcu_bh
+ * quiescent state.  Use "+" instead of "||" to defeat short circuiting.
+ */
+void rcu_sched_qs(int cpu)
+{
+	if (rcu_qsctr_help(&rcu_ctrlblk) + rcu_qsctr_help(&rcu_bh_ctrlblk))
+		raise_softirq(RCU_SOFTIRQ);
+}
+
+/*
+ * Record an rcu_bh quiescent state.
+ */
+void rcu_bh_qs(int cpu)
+{
+	if (rcu_qsctr_help(&rcu_bh_ctrlblk))
+		raise_softirq(RCU_SOFTIRQ);
+}
+
+/*
+ * Check to see if the scheduling-clock interrupt came from an extended
+ * quiescent state, and, if so, tell RCU about it.
+ */
+void rcu_check_callbacks(int cpu, int user)
+{
+	if (user ||
+	    (idle_cpu(cpu) &&
+	     !in_softirq() &&
+	     hardirq_count() <= (1 << HARDIRQ_SHIFT)))
+		rcu_sched_qs(cpu);
+	else if (!in_softirq())
+		rcu_bh_qs(cpu);
+}
+
+/*
+ * Helper function for rcu_process_callbacks() that operates on the
+ * specified rcu_ctrlkblk structure.
+ */
+static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
+{
+	unsigned long flags;
+	struct rcu_head *next, *list;
+
+	/* If no RCU callbacks ready to invoke, just return. */
+	if (&rcp->rcucblist == rcp->donetail)
+		return;
+
+	/* Move the ready-to-invoke callbacks to a local list. */
+	local_irq_save(flags);
+	list = rcp->rcucblist;
+	rcp->rcucblist = *rcp->donetail;
+	*rcp->donetail = NULL;
+	if (rcp->curtail == rcp->donetail)
+		rcp->curtail = &rcp->rcucblist;
+	rcp->donetail = &rcp->rcucblist;
+	local_irq_restore(flags);
+
+	/* Invoke the callbacks on the local list. */
+	while (list) {
+		next = list->next;
+		prefetch(next);
+		list->func(list);
+		list = next;
+	}
+}
+
+/*
+ * Invoke any callbacks whose grace period has completed.
+ */
+static void rcu_process_callbacks(struct softirq_action *unused)
+{
+	__rcu_process_callbacks(&rcu_ctrlblk);
+	__rcu_process_callbacks(&rcu_bh_ctrlblk);
+}
+
+/*
+ * Null function to handle CPU being onlined.  Longer term, we want to
+ * make TINY_RCU avoid using rcupdate.c, but later...
+ */
+int rcu_cpu_notify(struct notifier_block *self,
+		   unsigned long action, void *hcpu)
+{
+	return NOTIFY_OK;
+}
+
+/*
+ * Wait for a grace period to elapse.  But it is illegal to invoke
+ * synchronize_sched() from within an RCU read-side critical section.
+ * Therefore, any legal call to synchronize_sched() is a quiescent
+ * state, and so on a UP system, synchronize_sched() need do nothing.
+ * Ditto for synchronize_rcu_bh().  (But Lai Jiangshan points out the
+ * benefits of doing might_sleep() to reduce latency.)
+ *
+ * Cool, huh?  (Due to Josh Triplett.)
+ *
+ * But we want to make this a static inline later.
+ */
+void synchronize_sched(void)
+{
+	cond_resched();
+}
+EXPORT_SYMBOL_GPL(synchronize_sched);
+
+void synchronize_rcu_bh(void)
+{
+	synchronize_sched();
+}
+EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
+
+/*
+ * Helper function for call_rcu() and call_rcu_bh().
+ */
+static void __call_rcu(struct rcu_head *head,
+		       void (*func)(struct rcu_head *rcu),
+		       struct rcu_ctrlblk *rcp)
+{
+	unsigned long flags;
+
+	head->func = func;
+	head->next = NULL;
+	local_irq_save(flags);
+	*rcp->curtail = head;
+	rcp->curtail = &head->next;
+	local_irq_restore(flags);
+}
+
+/*
+ * Post an RCU callback to be invoked after the end of an RCU grace
+ * period.  But since we have but one CPU, that would be after any
+ * quiescent state.
+ */
+void call_rcu(struct rcu_head *head,
+	      void (*func)(struct rcu_head *rcu))
+{
+	__call_rcu(head, func, &rcu_ctrlblk);
+}
+EXPORT_SYMBOL_GPL(call_rcu);
+
+/*
+ * Post an RCU bottom-half callback to be invoked after any subsequent
+ * quiescent state.
+ */
+void call_rcu_bh(struct rcu_head *head,
+		 void (*func)(struct rcu_head *rcu))
+{
+	__call_rcu(head, func, &rcu_bh_ctrlblk);
+}
+EXPORT_SYMBOL_GPL(call_rcu_bh);
+
+void rcu_barrier(void)
+{
+	struct rcu_synchronize rcu;
+
+	init_completion(&rcu.completion);
+	/* Will wake me after RCU finished. */
+	call_rcu(&rcu.head, wakeme_after_rcu);
+	/* Wait for it. */
+	wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier);
+
+void rcu_barrier_bh(void)
+{
+	struct rcu_synchronize rcu;
+
+	init_completion(&rcu.completion);
+	/* Will wake me after RCU finished. */
+	call_rcu_bh(&rcu.head, wakeme_after_rcu);
+	/* Wait for it. */
+	wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_bh);
+
+void rcu_barrier_sched(void)
+{
+	struct rcu_synchronize rcu;
+
+	init_completion(&rcu.completion);
+	/* Will wake me after RCU finished. */
+	call_rcu_sched(&rcu.head, wakeme_after_rcu);
+	/* Wait for it. */
+	wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_sched);
+
+void __rcu_init(void)
+{
+	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+}
-- 
1.5.2.5

[PATCH tip/core/rcu 2/6] rcu: Add synchronize_srcu_expedited()

[Paul E. McKenney]

From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This patch creates a synchronize_srcu_expedited() that uses
synchronize_sched_expedited() where synchronize_srcu()
uses synchronize_sched().  The synchronize_srcu() and
synchronize_srcu_expedited() functions become one-liners that pass
synchronize_sched() or synchronize_sched_expedited(), repectively,
to a new __synchronize_srcu() function.

While in the file, move the EXPORT_SYMBOL_GPL()s to immediately
follow the corresponding functions.

Requested-by: Avi Kivity <avi@redhat.com>
Tested-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 include/linux/srcu.h |    1 +
 kernel/srcu.c        |   74 ++++++++++++++++++++++++++++++++++---------------
 2 files changed, 52 insertions(+), 23 deletions(-)

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index aca0eee..4765d97 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -48,6 +48,7 @@ void cleanup_srcu_struct(struct srcu_struct *sp);
 int srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
 void srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
 void synchronize_srcu(struct srcu_struct *sp);
+void synchronize_srcu_expedited(struct srcu_struct *sp);
 long srcu_batches_completed(struct srcu_struct *sp);
 
 #endif
diff --git a/kernel/srcu.c b/kernel/srcu.c
index b0aeeaf..818d7d9 100644
--- a/kernel/srcu.c
+++ b/kernel/srcu.c
@@ -49,6 +49,7 @@ int init_srcu_struct(struct srcu_struct *sp)
 	sp->per_cpu_ref = alloc_percpu(struct srcu_struct_array);
 	return (sp->per_cpu_ref ? 0 : -ENOMEM);
 }
+EXPORT_SYMBOL_GPL(init_srcu_struct);
 
 /*
  * srcu_readers_active_idx -- returns approximate number of readers
@@ -97,6 +98,7 @@ void cleanup_srcu_struct(struct srcu_struct *sp)
 	free_percpu(sp->per_cpu_ref);
 	sp->per_cpu_ref = NULL;
 }
+EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
 
 /**
  * srcu_read_lock - register a new reader for an SRCU-protected structure.
@@ -118,6 +120,7 @@ int srcu_read_lock(struct srcu_struct *sp)
 	preempt_enable();
 	return idx;
 }
+EXPORT_SYMBOL_GPL(srcu_read_lock);
 
 /**
  * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
@@ -136,22 +139,12 @@ void srcu_read_unlock(struct srcu_struct *sp, int idx)
 	per_cpu_ptr(sp->per_cpu_ref, smp_processor_id())->c[idx]--;
 	preempt_enable();
 }
+EXPORT_SYMBOL_GPL(srcu_read_unlock);
 
-/**
- * synchronize_srcu - wait for prior SRCU read-side critical-section completion
- * @sp: srcu_struct with which to synchronize.
- *
- * Flip the completed counter, and wait for the old count to drain to zero.
- * As with classic RCU, the updater must use some separate means of
- * synchronizing concurrent updates.  Can block; must be called from
- * process context.
- *
- * Note that it is illegal to call synchornize_srcu() from the corresponding
- * SRCU read-side critical section; doing so will result in deadlock.
- * However, it is perfectly legal to call synchronize_srcu() on one
- * srcu_struct from some other srcu_struct's read-side critical section.
+/*
+ * Helper function for synchronize_srcu() and synchronize_srcu_expedited().
  */
-void synchronize_srcu(struct srcu_struct *sp)
+void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
 {
 	int idx;
 
@@ -173,7 +166,7 @@ void synchronize_srcu(struct srcu_struct *sp)
 		return;
 	}
 
-	synchronize_sched();  /* Force memory barrier on all CPUs. */
+	sync_func();  /* Force memory barrier on all CPUs. */
 
 	/*
 	 * The preceding synchronize_sched() ensures that any CPU that
@@ -190,7 +183,7 @@ void synchronize_srcu(struct srcu_struct *sp)
 	idx = sp->completed & 0x1;
 	sp->completed++;
 
-	synchronize_sched();  /* Force memory barrier on all CPUs. */
+	sync_func();  /* Force memory barrier on all CPUs. */
 
 	/*
 	 * At this point, because of the preceding synchronize_sched(),
@@ -203,7 +196,7 @@ void synchronize_srcu(struct srcu_struct *sp)
 	while (srcu_readers_active_idx(sp, idx))
 		schedule_timeout_interruptible(1);
 
-	synchronize_sched();  /* Force memory barrier on all CPUs. */
+	sync_func();  /* Force memory barrier on all CPUs. */
 
 	/*
 	 * The preceding synchronize_sched() forces all srcu_read_unlock()
@@ -237,6 +230,47 @@ void synchronize_srcu(struct srcu_struct *sp)
 }
 
 /**
+ * synchronize_srcu - wait for prior SRCU read-side critical-section completion
+ * @sp: srcu_struct with which to synchronize.
+ *
+ * Flip the completed counter, and wait for the old count to drain to zero.
+ * As with classic RCU, the updater must use some separate means of
+ * synchronizing concurrent updates.  Can block; must be called from
+ * process context.
+ *
+ * Note that it is illegal to call synchronize_srcu() from the corresponding
+ * SRCU read-side critical section; doing so will result in deadlock.
+ * However, it is perfectly legal to call synchronize_srcu() on one
+ * srcu_struct from some other srcu_struct's read-side critical section.
+ */
+void synchronize_srcu(struct srcu_struct *sp)
+{
+	__synchronize_srcu(sp, synchronize_sched);
+}
+EXPORT_SYMBOL_GPL(synchronize_srcu);
+
+/**
+ * synchronize_srcu_expedited - like synchronize_srcu, but less patient
+ * @sp: srcu_struct with which to synchronize.
+ *
+ * Flip the completed counter, and wait for the old count to drain to zero.
+ * As with classic RCU, the updater must use some separate means of
+ * synchronizing concurrent updates.  Can block; must be called from
+ * process context.
+ *
+ * Note that it is illegal to call synchronize_srcu_expedited()
+ * from the corresponding SRCU read-side critical section; doing so
+ * will result in deadlock.  However, it is perfectly legal to call
+ * synchronize_srcu_expedited() on one srcu_struct from some other
+ * srcu_struct's read-side critical section.
+ */
+void synchronize_srcu_expedited(struct srcu_struct *sp)
+{
+	__synchronize_srcu(sp, synchronize_sched_expedited);
+}
+EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
+
+/**
  * srcu_batches_completed - return batches completed.
  * @sp: srcu_struct on which to report batch completion.
  *
@@ -248,10 +282,4 @@ long srcu_batches_completed(struct srcu_struct *sp)
 {
 	return sp->completed;
 }
-
-EXPORT_SYMBOL_GPL(init_srcu_struct);
-EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
-EXPORT_SYMBOL_GPL(srcu_read_lock);
-EXPORT_SYMBOL_GPL(srcu_read_unlock);
-EXPORT_SYMBOL_GPL(synchronize_srcu);
 EXPORT_SYMBOL_GPL(srcu_batches_completed);
-- 
1.5.2.5

[PATCH tip/core/rcu 3/6] rcu: add synchronize_srcu_expedited() to the rcutorture test suite

[Paul E. McKenney]

From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Adds the "srcu_expedited" torture type, and also renames sched_ops_sync
to sched_sync_ops for consistency while we are in this file.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcutorture.c |   25 ++++++++++++++++++++++---
 1 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 697c0a0..14480e8 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -547,6 +547,25 @@ static struct rcu_torture_ops srcu_ops = {
 	.name		= "srcu"
 };
 
+static void srcu_torture_synchronize_expedited(void)
+{
+	synchronize_srcu_expedited(&srcu_ctl);
+}
+
+static struct rcu_torture_ops srcu_expedited_ops = {
+	.init		= srcu_torture_init,
+	.cleanup	= srcu_torture_cleanup,
+	.readlock	= srcu_torture_read_lock,
+	.read_delay	= srcu_read_delay,
+	.readunlock	= srcu_torture_read_unlock,
+	.completed	= srcu_torture_completed,
+	.deferred_free	= rcu_sync_torture_deferred_free,
+	.sync		= srcu_torture_synchronize_expedited,
+	.cb_barrier	= NULL,
+	.stats		= srcu_torture_stats,
+	.name		= "srcu_expedited"
+};
+
 /*
  * Definitions for sched torture testing.
  */
@@ -592,7 +611,7 @@ static struct rcu_torture_ops sched_ops = {
 	.name		= "sched"
 };
 
-static struct rcu_torture_ops sched_ops_sync = {
+static struct rcu_torture_ops sched_sync_ops = {
 	.init		= rcu_sync_torture_init,
 	.cleanup	= NULL,
 	.readlock	= sched_torture_read_lock,
@@ -1098,8 +1117,8 @@ rcu_torture_init(void)
 	int firsterr = 0;
 	static struct rcu_torture_ops *torture_ops[] =
 		{ &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
-		  &sched_expedited_ops,
-		  &srcu_ops, &sched_ops, &sched_ops_sync, };
+		  &srcu_ops, &srcu_expedited_ops,
+		  &sched_ops, &sched_sync_ops, &sched_expedited_ops, };
 
 	mutex_lock(&fullstop_mutex);
 
-- 
1.5.2.5

[PATCH tip/core/rcu 4/6] rcu: add synchronize_srcu_expedited() to the documentation

[Paul E. McKenney]

From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 Documentation/RCU/whatisRCU.txt |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index e41a7fe..d542ca2 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -830,7 +830,7 @@ sched:	Critical sections	Grace period		Barrier
 SRCU:	Critical sections	Grace period		Barrier
 
 	srcu_read_lock		synchronize_srcu	N/A
-	srcu_read_unlock
+	srcu_read_unlock	synchronize_srcu_expedited
 
 SRCU:	Initialization/cleanup
 	init_srcu_struct
-- 
1.5.2.5

[PATCH tip/core/rcu 5/6] rcu: Improve rcutorture diagnostics when bad torture_type specified

[Paul E. McKenney]

From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Make rcutorture list the available torture_type values when it doesn't
like the one specified.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcutorture.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 14480e8..3dd0ca2 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -1129,8 +1129,12 @@ rcu_torture_init(void)
 			break;
 	}
 	if (i == ARRAY_SIZE(torture_ops)) {
-		printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
+		printk(KERN_ALERT "rcu-torture: invalid torture type: \"%s\"\n",
 		       torture_type);
+		printk(KERN_ALERT "rcu-torture types:");
+		for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
+			printk(KERN_ALERT " %s", torture_ops[i]->name);
+		printk(KERN_ALERT "\n");
 		mutex_unlock(&fullstop_mutex);
 		return -EINVAL;
 	}
-- 
1.5.2.5

[PATCH tip/core/rcu 6/6] rcu: Simplify creating of lockdep class for root rcu_node

[Paul E. McKenney]

From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Use lockdep_set_class() to simplify the code and to avoid any additional
overhead in the !LOCKDEP case.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcutree.c |    5 ++---
 kernel/rcutree.h |    2 ++
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index ddbf111..f57c32e 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1666,8 +1666,7 @@ static void __init rcu_init_one(struct rcu_state *rsp)
 		cpustride *= rsp->levelspread[i];
 		rnp = rsp->level[i];
 		for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
-			if (rnp != rcu_get_root(rsp))
-				spin_lock_init(&rnp->lock);
+			spin_lock_init(&rnp->lock);
 			rnp->gpnum = 0;
 			rnp->qsmask = 0;
 			rnp->qsmaskinit = 0;
@@ -1690,7 +1689,7 @@ static void __init rcu_init_one(struct rcu_state *rsp)
 			INIT_LIST_HEAD(&rnp->blocked_tasks[1]);
 		}
 	}
-	spin_lock_init(&rcu_get_root(rsp)->lock);
+	lockdep_set_class(&rcu_get_root(rsp)->lock, &rcu_root_class);
 }
 
 /*
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 599161f..e091b30 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -296,6 +296,8 @@ DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
 
 #else /* #ifdef RCU_TREE_NONCORE */
 
+static struct lock_class_key rcu_root_class;
+
 /* Forward declarations for rcutree_plugin.h */
 static inline void rcu_bootup_announce(void);
 long rcu_batches_completed(void);
-- 
1.5.2.5

Re: [PATCH tip/core/rcu 0/6] rcu: Tiny RCU, expedited RCU, rcutorture fixes, lockdep simplification

[Josh Triplett]

On Sun, Oct 25, 2009 at 07:02:53PM -0700, Paul E. McKenney wrote:
> Updated patches for post 2.6.32:
> 
> o	RCU the Bloatwatch Edition, v8
> 
> o	Add synchronize_rcu_expedited().
> 
> o	Add rcutorture tests for synchronize_rcu_expedited().
> 
> o	Update RCU documentation for synchronize_rcu_expedited().
> 
> o	Make rcutorture list the torture types it knows about when
> 	complaining about the one specified.
> 
> o	Simplify creation of the separate lockdep class for the
> 	root rcu_node structure's lock.
> 
> 
>  b/Documentation/RCU/whatisRCU.txt |    3 
>  b/include/linux/hardirq.h         |   24 +++
>  b/include/linux/rcupdate.h        |    6 
>  b/include/linux/rcutiny.h         |   97 ++++++++++++
>  b/include/linux/srcu.h            |    1 
>  b/init/Kconfig                    |    9 +
>  b/kernel/Makefile                 |    1 
>  b/kernel/rcupdate.c               |    4 
>  b/kernel/rcutiny.c                |  295 +++++++++++++++++++++++++++++++++++++-
>  b/kernel/rcutorture.c             |   26 ++-
>  b/kernel/rcutree.c                |    5 
>  b/kernel/rcutree.h                |    3 
>  b/kernel/srcu.c                   |   75 ++++++---
>  kernel/rcutorture.c               |    7 
>  14 files changed, 519 insertions(+), 37 deletions(-)

For all 6 patches:
Acked-by: Josh Triplett <josh@joshtriplett.org>

Re: [PATCH tip/core/rcu 6/6] rcu: Simplify creating of lockdep class for root rcu_node

[Ingo Molnar]

* Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:

> From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> 
> Use lockdep_set_class() to simplify the code and to avoid any additional
> overhead in the !LOCKDEP case.
> 
> Signed-off-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This signoff order is wrong - first signoff line must be the author of 
the patch. (which is a pretty general rule with only rare exceptions) 

This patch was from Peter originally, right? In such cases please add:

  From: Peter Zijlstra <peterz@infradead.org>

To the head of the patch. Or, if Peter acked it, add:

  Acked-by: Peter Zijlstra <peterz@infradead.org>

SOB lines are strictly only added by people who send patches to you - 
i.e. it records the patch handling pathway.

Thanks,

	Ingo

Re: [PATCH tip/core/rcu 6/6] rcu: Simplify creating of lockdep class for root rcu_node

[Lai Jiangshan]

Paul E. McKenney wrote:
> diff --git a/kernel/rcutree.h b/kernel/rcutree.h
> index 599161f..e091b30 100644
> --- a/kernel/rcutree.h
> +++ b/kernel/rcutree.h
> @@ -296,6 +296,8 @@ DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
>  
>  #else /* #ifdef RCU_TREE_NONCORE */
>  
> +static struct lock_class_key rcu_root_class;
> +

I think this line needs to be moved into rcutree.c.

>  /* Forward declarations for rcutree_plugin.h */
>  static inline void rcu_bootup_announce(void);
>  long rcu_batches_completed(void);

For all 6 patches:
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>

[tip:core/rcu] rcu: "Tiny RCU", The Bloatwatch Edition

[tip-bot for Paul E. McKenney]

Commit-ID:  9b1d82fa1611706fa7ee1505f290160a18caf95d
Gitweb:     http://git.kernel.org/tip/9b1d82fa1611706fa7ee1505f290160a18caf95d
Author:     Paul E. McKenney <paulmck@linux.vnet.ibm.com>
AuthorDate: Sun, 25 Oct 2009 19:03:50 -0700
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 26 Oct 2009 09:40:29 +0100

rcu: "Tiny RCU", The Bloatwatch Edition

This patch is a version of RCU designed for !SMP provided for a
small-footprint RCU implementation.  In particular, the
implementation of synchronize_rcu() is extremely lightweight and
high performance. It passes rcutorture testing in each of the
four relevant configurations (combinations of NO_HZ and PREEMPT)
on x86.  This saves about 1K bytes compared to old Classic RCU
(which is no longer in mainline), and more than three kilobytes
compared to Hierarchical RCU (updated to 2.6.30):

	CONFIG_TREE_RCU:

	   text	   data	    bss	    dec	    filename
	    183       4       0     187     kernel/rcupdate.o
	   2783     520      36    3339     kernel/rcutree.o
				   3526 Total (vs 4565 for v7)

	CONFIG_TREE_PREEMPT_RCU:

	   text	   data	    bss	    dec	    filename
	    263       4       0     267     kernel/rcupdate.o
	   4594     776      52    5422     kernel/rcutree.o
	   			   5689 Total (6155 for v7)

	CONFIG_TINY_RCU:

	   text	   data	    bss	    dec	    filename
	     96       4       0     100     kernel/rcupdate.o
	    734      24       0     758     kernel/rcutiny.o
	    			    858 Total (vs 848 for v7)

The above is for x86.  Your mileage may vary on other platforms.
Further compression is possible, but is being procrastinated.

Changes from v7 (http://lkml.org/lkml/2009/10/9/388)

o	Apply Lai Jiangshan's review comments (aside from
might_sleep() 	in synchronize_sched(), which is covered by SMP builds).

o	Fix up expedited primitives.

Changes from v6 (http://lkml.org/lkml/2009/9/23/293).

o	Forward ported to put it into the 2.6.33 stream.

o	Added lockdep support.

o	Make lightweight rcu_barrier.

Changes from v5 (http://lkml.org/lkml/2009/6/23/12).

o	Ported to latest pre-2.6.32 merge window kernel.

	- Renamed rcu_qsctr_inc() to rcu_sched_qs().
	- Renamed rcu_bh_qsctr_inc() to rcu_bh_qs().
	- Provided trivial rcu_cpu_notify().
	- Provided trivial exit_rcu().
	- Provided trivial rcu_needs_cpu().
	- Fixed up the rcu_*_enter/exit() functions in linux/hardirq.h.

o	Removed the dependence on EMBEDDED, with a view to making
	TINY_RCU default for !SMP at some time in the future.

o	Added (trivial) support for expedited grace periods.

Changes from v4 (http://lkml.org/lkml/2009/5/2/91) include:

o	Squeeze the size down a bit further by removing the
	->completed field from struct rcu_ctrlblk.

o	This permits synchronize_rcu() to become the empty function.
	Previous concerns about rcutorture were unfounded, as
	rcutorture correctly handles a constant value from
	rcu_batches_completed() and rcu_batches_completed_bh().

Changes from v3 (http://lkml.org/lkml/2009/3/29/221) include:

o	Changed rcu_batches_completed(), rcu_batches_completed_bh()
	rcu_enter_nohz(), rcu_exit_nohz(), rcu_nmi_enter(), and
	rcu_nmi_exit(), to be static inlines, as suggested by David
	Howells.  Doing this saves about 100 bytes from rcutiny.o.
	(The numbers between v3 and this v4 of the patch are not directly
	comparable, since they are against different versions of Linux.)

Changes from v2 (http://lkml.org/lkml/2009/2/3/333) include:

o	Fix whitespace issues.

o	Change short-circuit "||" operator to instead be "+" in order
to 	fix performance bug noted by "kraai" on LWN.

		(http://lwn.net/Articles/324348/)

Changes from v1 (http://lkml.org/lkml/2009/1/13/440) include:

o	This version depends on EMBEDDED as well as !SMP, as suggested
	by Ingo.

o	Updated rcu_needs_cpu() to unconditionally return zero,
	permitting the CPU to enter dynticks-idle mode at any time.
	This works because callbacks can be invoked upon entry to
	dynticks-idle mode.

o	Paul is now OK with this being included, based on a poll at
the 	Kernel Miniconf at linux.conf.au, where about ten people said
	that they cared about saving 900 bytes on single-CPU systems.

o	Applies to both mainline and tip/core/rcu.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: David Howells <dhowells@redhat.com>
Acked-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: avi@redhat.com
Cc: mtosatti@redhat.com
LKML-Reference: <12565226351355-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 include/linux/hardirq.h  |   24 ++++
 include/linux/rcupdate.h |    6 +
 include/linux/rcutiny.h  |   97 +++++++++++++++
 init/Kconfig             |    9 ++
 kernel/Makefile          |    1 +
 kernel/rcupdate.c        |    4 +
 kernel/rcutiny.c         |  294 ++++++++++++++++++++++++++++++++++++++++++++++
 7 files changed, 435 insertions(+), 0 deletions(-)

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 6d527ee..d5b3876 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -139,10 +139,34 @@ static inline void account_system_vtime(struct task_struct *tsk)
 #endif
 
 #if defined(CONFIG_NO_HZ)
+#if defined(CONFIG_TINY_RCU)
+extern void rcu_enter_nohz(void);
+extern void rcu_exit_nohz(void);
+
+static inline void rcu_irq_enter(void)
+{
+	rcu_exit_nohz();
+}
+
+static inline void rcu_irq_exit(void)
+{
+	rcu_enter_nohz();
+}
+
+static inline void rcu_nmi_enter(void)
+{
+}
+
+static inline void rcu_nmi_exit(void)
+{
+}
+
+#else
 extern void rcu_irq_enter(void);
 extern void rcu_irq_exit(void);
 extern void rcu_nmi_enter(void);
 extern void rcu_nmi_exit(void);
+#endif
 #else
 # define rcu_irq_enter() do { } while (0)
 # define rcu_irq_exit() do { } while (0)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 3ebd0b7..6dd71fa 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -68,11 +68,17 @@ extern int sched_expedited_torture_stats(char *page);
 /* Internal to kernel */
 extern void rcu_init(void);
 extern void rcu_scheduler_starting(void);
+#ifndef CONFIG_TINY_RCU
 extern int rcu_needs_cpu(int cpu);
+#else
+static inline int rcu_needs_cpu(int cpu) { return 0; }
+#endif
 extern int rcu_scheduler_active;
 
 #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
 #include <linux/rcutree.h>
+#elif CONFIG_TINY_RCU
+#include <linux/rcutiny.h>
 #else
 #error "Unknown RCU implementation specified to kernel configuration"
 #endif
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
new file mode 100644
index 0000000..891073c
--- /dev/null
+++ b/include/linux/rcutiny.h
@@ -0,0 +1,97 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright IBM Corporation, 2008
+ *
+ * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * 		Documentation/RCU
+ */
+
+#ifndef __LINUX_TINY_H
+#define __LINUX_TINY_H
+
+#include <linux/cache.h>
+
+void rcu_sched_qs(int cpu);
+void rcu_bh_qs(int cpu);
+
+#define __rcu_read_lock()	preempt_disable()
+#define __rcu_read_unlock()	preempt_enable()
+#define __rcu_read_lock_bh()	local_bh_disable()
+#define __rcu_read_unlock_bh()	local_bh_enable()
+#define call_rcu_sched		call_rcu
+
+#define rcu_init_sched()	do { } while (0)
+extern void rcu_check_callbacks(int cpu, int user);
+extern void __rcu_init(void);
+
+/*
+ * Return the number of grace periods.
+ */
+static inline long rcu_batches_completed(void)
+{
+	return 0;
+}
+
+/*
+ * Return the number of bottom-half grace periods.
+ */
+static inline long rcu_batches_completed_bh(void)
+{
+	return 0;
+}
+
+extern int rcu_expedited_torture_stats(char *page);
+
+static inline void synchronize_rcu_expedited(void)
+{
+	synchronize_sched();
+}
+
+static inline void synchronize_rcu_bh_expedited(void)
+{
+	synchronize_sched();
+}
+
+struct notifier_block;
+extern int rcu_cpu_notify(struct notifier_block *self,
+			  unsigned long action, void *hcpu);
+
+#ifdef CONFIG_NO_HZ
+
+extern void rcu_enter_nohz(void);
+extern void rcu_exit_nohz(void);
+
+#else /* #ifdef CONFIG_NO_HZ */
+
+static inline void rcu_enter_nohz(void)
+{
+}
+
+static inline void rcu_exit_nohz(void)
+{
+}
+
+#endif /* #else #ifdef CONFIG_NO_HZ */
+
+static inline void exit_rcu(void)
+{
+}
+
+#endif /* __LINUX_RCUTINY_H */
diff --git a/init/Kconfig b/init/Kconfig
index 09c5c64..d367bf6 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -334,6 +334,15 @@ config TREE_PREEMPT_RCU
 	  is also required.  It also scales down nicely to
 	  smaller systems.
 
+config TINY_RCU
+	bool "UP-only small-memory-footprint RCU"
+	depends on !SMP
+	help
+	  This option selects the RCU implementation that is
+	  designed for UP systems from which real-time response
+	  is not required.  This option greatly reduces the
+	  memory footprint of RCU.
+
 endchoice
 
 config RCU_TRACE
diff --git a/kernel/Makefile b/kernel/Makefile
index b8d4cd8..e9a0e6e 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -82,6 +82,7 @@ obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
 obj-$(CONFIG_TREE_RCU) += rcutree.o
 obj-$(CONFIG_TREE_PREEMPT_RCU) += rcutree.o
 obj-$(CONFIG_TREE_RCU_TRACE) += rcutree_trace.o
+obj-$(CONFIG_TINY_RCU) += rcutiny.o
 obj-$(CONFIG_RELAY) += relay.o
 obj-$(CONFIG_SYSCTL) += utsname_sysctl.o
 obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 4001833..7625f20 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -67,6 +67,8 @@ void wakeme_after_rcu(struct rcu_head  *head)
 	complete(&rcu->completion);
 }
 
+#ifndef CONFIG_TINY_RCU
+
 #ifdef CONFIG_TREE_PREEMPT_RCU
 
 /**
@@ -157,6 +159,8 @@ void synchronize_rcu_bh(void)
 }
 EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
 
+#endif /* #ifndef CONFIG_TINY_RCU */
+
 static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,
 		unsigned long action, void *hcpu)
 {
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
new file mode 100644
index 0000000..0b54efd
--- /dev/null
+++ b/kernel/rcutiny.c
@@ -0,0 +1,294 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright IBM Corporation, 2008
+ *
+ * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * 		Documentation/RCU
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/notifier.h>
+#include <linux/cpu.h>
+#include <linux/mutex.h>
+#include <linux/time.h>
+
+/* Global control variables for rcupdate callback mechanism. */
+struct rcu_ctrlblk {
+	struct rcu_head *rcucblist;	/* List of pending callbacks (CBs). */
+	struct rcu_head **donetail;	/* ->next pointer of last "done" CB. */
+	struct rcu_head **curtail;	/* ->next pointer of last CB. */
+};
+
+/* Definition for rcupdate control block. */
+static struct rcu_ctrlblk rcu_ctrlblk = {
+	.rcucblist = NULL,
+	.donetail = &rcu_ctrlblk.rcucblist,
+	.curtail = &rcu_ctrlblk.rcucblist,
+};
+static struct rcu_ctrlblk rcu_bh_ctrlblk = {
+	.rcucblist = NULL,
+	.donetail = &rcu_bh_ctrlblk.rcucblist,
+	.curtail = &rcu_bh_ctrlblk.rcucblist,
+};
+
+#ifdef CONFIG_NO_HZ
+
+static long rcu_dynticks_nesting = 1;
+
+/*
+ * Enter dynticks-idle mode, which is an extended quiescent state
+ * if we have fully entered that mode (i.e., if the new value of
+ * dynticks_nesting is zero).
+ */
+void rcu_enter_nohz(void)
+{
+	if (--rcu_dynticks_nesting == 0)
+		rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
+}
+
+/*
+ * Exit dynticks-idle mode, so that we are no longer in an extended
+ * quiescent state.
+ */
+void rcu_exit_nohz(void)
+{
+	rcu_dynticks_nesting++;
+}
+
+#endif /* #ifdef CONFIG_NO_HZ */
+
+/*
+ * Helper function for rcu_qsctr_inc() and rcu_bh_qsctr_inc().
+ * Also disable irqs to avoid confusion due to interrupt handlers invoking
+ * call_rcu().
+ */
+static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	if (rcp->rcucblist != NULL &&
+	    rcp->donetail != rcp->curtail) {
+		rcp->donetail = rcp->curtail;
+		local_irq_restore(flags);
+		return 1;
+	}
+	local_irq_restore(flags);
+	return 0;
+}
+
+/*
+ * Record an rcu quiescent state.  And an rcu_bh quiescent state while we
+ * are at it, given that any rcu quiescent state is also an rcu_bh
+ * quiescent state.  Use "+" instead of "||" to defeat short circuiting.
+ */
+void rcu_sched_qs(int cpu)
+{
+	if (rcu_qsctr_help(&rcu_ctrlblk) + rcu_qsctr_help(&rcu_bh_ctrlblk))
+		raise_softirq(RCU_SOFTIRQ);
+}
+
+/*
+ * Record an rcu_bh quiescent state.
+ */
+void rcu_bh_qs(int cpu)
+{
+	if (rcu_qsctr_help(&rcu_bh_ctrlblk))
+		raise_softirq(RCU_SOFTIRQ);
+}
+
+/*
+ * Check to see if the scheduling-clock interrupt came from an extended
+ * quiescent state, and, if so, tell RCU about it.
+ */
+void rcu_check_callbacks(int cpu, int user)
+{
+	if (user ||
+	    (idle_cpu(cpu) &&
+	     !in_softirq() &&
+	     hardirq_count() <= (1 << HARDIRQ_SHIFT)))
+		rcu_sched_qs(cpu);
+	else if (!in_softirq())
+		rcu_bh_qs(cpu);
+}
+
+/*
+ * Helper function for rcu_process_callbacks() that operates on the
+ * specified rcu_ctrlkblk structure.
+ */
+static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
+{
+	unsigned long flags;
+	struct rcu_head *next, *list;
+
+	/* If no RCU callbacks ready to invoke, just return. */
+	if (&rcp->rcucblist == rcp->donetail)
+		return;
+
+	/* Move the ready-to-invoke callbacks to a local list. */
+	local_irq_save(flags);
+	list = rcp->rcucblist;
+	rcp->rcucblist = *rcp->donetail;
+	*rcp->donetail = NULL;
+	if (rcp->curtail == rcp->donetail)
+		rcp->curtail = &rcp->rcucblist;
+	rcp->donetail = &rcp->rcucblist;
+	local_irq_restore(flags);
+
+	/* Invoke the callbacks on the local list. */
+	while (list) {
+		next = list->next;
+		prefetch(next);
+		list->func(list);
+		list = next;
+	}
+}
+
+/*
+ * Invoke any callbacks whose grace period has completed.
+ */
+static void rcu_process_callbacks(struct softirq_action *unused)
+{
+	__rcu_process_callbacks(&rcu_ctrlblk);
+	__rcu_process_callbacks(&rcu_bh_ctrlblk);
+}
+
+/*
+ * Null function to handle CPU being onlined.  Longer term, we want to
+ * make TINY_RCU avoid using rcupdate.c, but later...
+ */
+int rcu_cpu_notify(struct notifier_block *self,
+		   unsigned long action, void *hcpu)
+{
+	return NOTIFY_OK;
+}
+
+/*
+ * Wait for a grace period to elapse.  But it is illegal to invoke
+ * synchronize_sched() from within an RCU read-side critical section.
+ * Therefore, any legal call to synchronize_sched() is a quiescent
+ * state, and so on a UP system, synchronize_sched() need do nothing.
+ * Ditto for synchronize_rcu_bh().  (But Lai Jiangshan points out the
+ * benefits of doing might_sleep() to reduce latency.)
+ *
+ * Cool, huh?  (Due to Josh Triplett.)
+ *
+ * But we want to make this a static inline later.
+ */
+void synchronize_sched(void)
+{
+	cond_resched();
+}
+EXPORT_SYMBOL_GPL(synchronize_sched);
+
+void synchronize_rcu_bh(void)
+{
+	synchronize_sched();
+}
+EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
+
+/*
+ * Helper function for call_rcu() and call_rcu_bh().
+ */
+static void __call_rcu(struct rcu_head *head,
+		       void (*func)(struct rcu_head *rcu),
+		       struct rcu_ctrlblk *rcp)
+{
+	unsigned long flags;
+
+	head->func = func;
+	head->next = NULL;
+	local_irq_save(flags);
+	*rcp->curtail = head;
+	rcp->curtail = &head->next;
+	local_irq_restore(flags);
+}
+
+/*
+ * Post an RCU callback to be invoked after the end of an RCU grace
+ * period.  But since we have but one CPU, that would be after any
+ * quiescent state.
+ */
+void call_rcu(struct rcu_head *head,
+	      void (*func)(struct rcu_head *rcu))
+{
+	__call_rcu(head, func, &rcu_ctrlblk);
+}
+EXPORT_SYMBOL_GPL(call_rcu);
+
+/*
+ * Post an RCU bottom-half callback to be invoked after any subsequent
+ * quiescent state.
+ */
+void call_rcu_bh(struct rcu_head *head,
+		 void (*func)(struct rcu_head *rcu))
+{
+	__call_rcu(head, func, &rcu_bh_ctrlblk);
+}
+EXPORT_SYMBOL_GPL(call_rcu_bh);
+
+void rcu_barrier(void)
+{
+	struct rcu_synchronize rcu;
+
+	init_completion(&rcu.completion);
+	/* Will wake me after RCU finished. */
+	call_rcu(&rcu.head, wakeme_after_rcu);
+	/* Wait for it. */
+	wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier);
+
+void rcu_barrier_bh(void)
+{
+	struct rcu_synchronize rcu;
+
+	init_completion(&rcu.completion);
+	/* Will wake me after RCU finished. */
+	call_rcu_bh(&rcu.head, wakeme_after_rcu);
+	/* Wait for it. */
+	wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_bh);
+
+void rcu_barrier_sched(void)
+{
+	struct rcu_synchronize rcu;
+
+	init_completion(&rcu.completion);
+	/* Will wake me after RCU finished. */
+	call_rcu_sched(&rcu.head, wakeme_after_rcu);
+	/* Wait for it. */
+	wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_sched);
+
+void __rcu_init(void)
+{
+	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+}

[tip:core/rcu] rcu: Add synchronize_srcu_expedited()

[tip-bot for Paul E. McKenney]

Commit-ID:  0cd397d33608ae6c97d2ee6c8c43462b419b7e26
Gitweb:     http://git.kernel.org/tip/0cd397d33608ae6c97d2ee6c8c43462b419b7e26
Author:     Paul E. McKenney <paulmck@linux.vnet.ibm.com>
AuthorDate: Sun, 25 Oct 2009 19:03:51 -0700
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 26 Oct 2009 09:40:30 +0100

rcu: Add synchronize_srcu_expedited()

This patch creates a synchronize_srcu_expedited() that uses
synchronize_sched_expedited() where synchronize_srcu()
uses synchronize_sched().  The synchronize_srcu() and
synchronize_srcu_expedited() functions become one-liners that
pass synchronize_sched() or synchronize_sched_expedited(),
repectively, to a new __synchronize_srcu() function.

While in the file, move the EXPORT_SYMBOL_GPL()s to immediately
follow the corresponding functions.

Requested-by: Avi Kivity <avi@redhat.com>
Tested-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: avi@redhat.com
LKML-Reference: <12565226354038-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 include/linux/srcu.h |    1 +
 kernel/srcu.c        |   74 ++++++++++++++++++++++++++++++++++---------------
 2 files changed, 52 insertions(+), 23 deletions(-)

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index aca0eee..4765d97 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -48,6 +48,7 @@ void cleanup_srcu_struct(struct srcu_struct *sp);
 int srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
 void srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
 void synchronize_srcu(struct srcu_struct *sp);
+void synchronize_srcu_expedited(struct srcu_struct *sp);
 long srcu_batches_completed(struct srcu_struct *sp);
 
 #endif
diff --git a/kernel/srcu.c b/kernel/srcu.c
index b0aeeaf..818d7d9 100644
--- a/kernel/srcu.c
+++ b/kernel/srcu.c
@@ -49,6 +49,7 @@ int init_srcu_struct(struct srcu_struct *sp)
 	sp->per_cpu_ref = alloc_percpu(struct srcu_struct_array);
 	return (sp->per_cpu_ref ? 0 : -ENOMEM);
 }
+EXPORT_SYMBOL_GPL(init_srcu_struct);
 
 /*
  * srcu_readers_active_idx -- returns approximate number of readers
@@ -97,6 +98,7 @@ void cleanup_srcu_struct(struct srcu_struct *sp)
 	free_percpu(sp->per_cpu_ref);
 	sp->per_cpu_ref = NULL;
 }
+EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
 
 /**
  * srcu_read_lock - register a new reader for an SRCU-protected structure.
@@ -118,6 +120,7 @@ int srcu_read_lock(struct srcu_struct *sp)
 	preempt_enable();
 	return idx;
 }
+EXPORT_SYMBOL_GPL(srcu_read_lock);
 
 /**
  * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
@@ -136,22 +139,12 @@ void srcu_read_unlock(struct srcu_struct *sp, int idx)
 	per_cpu_ptr(sp->per_cpu_ref, smp_processor_id())->c[idx]--;
 	preempt_enable();
 }
+EXPORT_SYMBOL_GPL(srcu_read_unlock);
 
-/**
- * synchronize_srcu - wait for prior SRCU read-side critical-section completion
- * @sp: srcu_struct with which to synchronize.
- *
- * Flip the completed counter, and wait for the old count to drain to zero.
- * As with classic RCU, the updater must use some separate means of
- * synchronizing concurrent updates.  Can block; must be called from
- * process context.
- *
- * Note that it is illegal to call synchornize_srcu() from the corresponding
- * SRCU read-side critical section; doing so will result in deadlock.
- * However, it is perfectly legal to call synchronize_srcu() on one
- * srcu_struct from some other srcu_struct's read-side critical section.
+/*
+ * Helper function for synchronize_srcu() and synchronize_srcu_expedited().
  */
-void synchronize_srcu(struct srcu_struct *sp)
+void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
 {
 	int idx;
 
@@ -173,7 +166,7 @@ void synchronize_srcu(struct srcu_struct *sp)
 		return;
 	}
 
-	synchronize_sched();  /* Force memory barrier on all CPUs. */
+	sync_func();  /* Force memory barrier on all CPUs. */
 
 	/*
 	 * The preceding synchronize_sched() ensures that any CPU that
@@ -190,7 +183,7 @@ void synchronize_srcu(struct srcu_struct *sp)
 	idx = sp->completed & 0x1;
 	sp->completed++;
 
-	synchronize_sched();  /* Force memory barrier on all CPUs. */
+	sync_func();  /* Force memory barrier on all CPUs. */
 
 	/*
 	 * At this point, because of the preceding synchronize_sched(),
@@ -203,7 +196,7 @@ void synchronize_srcu(struct srcu_struct *sp)
 	while (srcu_readers_active_idx(sp, idx))
 		schedule_timeout_interruptible(1);
 
-	synchronize_sched();  /* Force memory barrier on all CPUs. */
+	sync_func();  /* Force memory barrier on all CPUs. */
 
 	/*
 	 * The preceding synchronize_sched() forces all srcu_read_unlock()
@@ -237,6 +230,47 @@ void synchronize_srcu(struct srcu_struct *sp)
 }
 
 /**
+ * synchronize_srcu - wait for prior SRCU read-side critical-section completion
+ * @sp: srcu_struct with which to synchronize.
+ *
+ * Flip the completed counter, and wait for the old count to drain to zero.
+ * As with classic RCU, the updater must use some separate means of
+ * synchronizing concurrent updates.  Can block; must be called from
+ * process context.
+ *
+ * Note that it is illegal to call synchronize_srcu() from the corresponding
+ * SRCU read-side critical section; doing so will result in deadlock.
+ * However, it is perfectly legal to call synchronize_srcu() on one
+ * srcu_struct from some other srcu_struct's read-side critical section.
+ */
+void synchronize_srcu(struct srcu_struct *sp)
+{
+	__synchronize_srcu(sp, synchronize_sched);
+}
+EXPORT_SYMBOL_GPL(synchronize_srcu);
+
+/**
+ * synchronize_srcu_expedited - like synchronize_srcu, but less patient
+ * @sp: srcu_struct with which to synchronize.
+ *
+ * Flip the completed counter, and wait for the old count to drain to zero.
+ * As with classic RCU, the updater must use some separate means of
+ * synchronizing concurrent updates.  Can block; must be called from
+ * process context.
+ *
+ * Note that it is illegal to call synchronize_srcu_expedited()
+ * from the corresponding SRCU read-side critical section; doing so
+ * will result in deadlock.  However, it is perfectly legal to call
+ * synchronize_srcu_expedited() on one srcu_struct from some other
+ * srcu_struct's read-side critical section.
+ */
+void synchronize_srcu_expedited(struct srcu_struct *sp)
+{
+	__synchronize_srcu(sp, synchronize_sched_expedited);
+}
+EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
+
+/**
  * srcu_batches_completed - return batches completed.
  * @sp: srcu_struct on which to report batch completion.
  *
@@ -248,10 +282,4 @@ long srcu_batches_completed(struct srcu_struct *sp)
 {
 	return sp->completed;
 }
-
-EXPORT_SYMBOL_GPL(init_srcu_struct);
-EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
-EXPORT_SYMBOL_GPL(srcu_read_lock);
-EXPORT_SYMBOL_GPL(srcu_read_unlock);
-EXPORT_SYMBOL_GPL(synchronize_srcu);
 EXPORT_SYMBOL_GPL(srcu_batches_completed);

[tip:core/rcu] rcu: Add synchronize_srcu_expedited() to the rcutorture test suite

[tip-bot for Paul E. McKenney]

Commit-ID:  804bb8370522a569bd3a732b9de5fbd55e26f155
Gitweb:     http://git.kernel.org/tip/804bb8370522a569bd3a732b9de5fbd55e26f155
Author:     Paul E. McKenney <paulmck@linux.vnet.ibm.com>
AuthorDate: Sun, 25 Oct 2009 19:03:52 -0700
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 26 Oct 2009 09:40:30 +0100

rcu: Add synchronize_srcu_expedited() to the rcutorture test suite

Adds the "srcu_expedited" torture type, and also renames
sched_ops_sync to sched_sync_ops for consistency while we are in
this file.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: avi@redhat.com
Cc: mtosatti@redhat.com
LKML-Reference: <12565226353636-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/rcutorture.c |   25 ++++++++++++++++++++++---
 1 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 697c0a0..14480e8 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -547,6 +547,25 @@ static struct rcu_torture_ops srcu_ops = {
 	.name		= "srcu"
 };
 
+static void srcu_torture_synchronize_expedited(void)
+{
+	synchronize_srcu_expedited(&srcu_ctl);
+}
+
+static struct rcu_torture_ops srcu_expedited_ops = {
+	.init		= srcu_torture_init,
+	.cleanup	= srcu_torture_cleanup,
+	.readlock	= srcu_torture_read_lock,
+	.read_delay	= srcu_read_delay,
+	.readunlock	= srcu_torture_read_unlock,
+	.completed	= srcu_torture_completed,
+	.deferred_free	= rcu_sync_torture_deferred_free,
+	.sync		= srcu_torture_synchronize_expedited,
+	.cb_barrier	= NULL,
+	.stats		= srcu_torture_stats,
+	.name		= "srcu_expedited"
+};
+
 /*
  * Definitions for sched torture testing.
  */
@@ -592,7 +611,7 @@ static struct rcu_torture_ops sched_ops = {
 	.name		= "sched"
 };
 
-static struct rcu_torture_ops sched_ops_sync = {
+static struct rcu_torture_ops sched_sync_ops = {
 	.init		= rcu_sync_torture_init,
 	.cleanup	= NULL,
 	.readlock	= sched_torture_read_lock,
@@ -1098,8 +1117,8 @@ rcu_torture_init(void)
 	int firsterr = 0;
 	static struct rcu_torture_ops *torture_ops[] =
 		{ &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
-		  &sched_expedited_ops,
-		  &srcu_ops, &sched_ops, &sched_ops_sync, };
+		  &srcu_ops, &srcu_expedited_ops,
+		  &sched_ops, &sched_sync_ops, &sched_expedited_ops, };
 
 	mutex_lock(&fullstop_mutex);
 

[tip:core/rcu] rcu: Add synchronize_srcu_expedited() to the documentation

[tip-bot for Paul E. McKenney]

Commit-ID:  64179861cb801eac4f00c79f39a29ea5ac9470d7
Gitweb:     http://git.kernel.org/tip/64179861cb801eac4f00c79f39a29ea5ac9470d7
Author:     Paul E. McKenney <paulmck@linux.vnet.ibm.com>
AuthorDate: Sun, 25 Oct 2009 19:03:53 -0700
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 26 Oct 2009 09:40:31 +0100

rcu: Add synchronize_srcu_expedited() to the documentation

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: avi@redhat.com
Cc: mtosatti@redhat.com
LKML-Reference: <12565226354176-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 Documentation/RCU/whatisRCU.txt |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index e41a7fe..d542ca2 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -830,7 +830,7 @@ sched:	Critical sections	Grace period		Barrier
 SRCU:	Critical sections	Grace period		Barrier
 
 	srcu_read_lock		synchronize_srcu	N/A
-	srcu_read_unlock
+	srcu_read_unlock	synchronize_srcu_expedited
 
 SRCU:	Initialization/cleanup
 	init_srcu_struct

[tip:core/rcu] rcu: Improve rcutorture diagnostics when bad torture_type specified

[tip-bot for Paul E. McKenney]

Commit-ID:  cf886c44ec418a01b2c52493465accb81acbf930
Gitweb:     http://git.kernel.org/tip/cf886c44ec418a01b2c52493465accb81acbf930
Author:     Paul E. McKenney <paulmck@linux.vnet.ibm.com>
AuthorDate: Sun, 25 Oct 2009 19:03:54 -0700
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 26 Oct 2009 09:40:31 +0100

rcu: Improve rcutorture diagnostics when bad torture_type specified

Make rcutorture list the available torture_type values when it
doesn't like the one specified.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: avi@redhat.com
Cc: mtosatti@redhat.com
LKML-Reference: <12565226351868-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/rcutorture.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 14480e8..3dd0ca2 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -1129,8 +1129,12 @@ rcu_torture_init(void)
 			break;
 	}
 	if (i == ARRAY_SIZE(torture_ops)) {
-		printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
+		printk(KERN_ALERT "rcu-torture: invalid torture type: \"%s\"\n",
 		       torture_type);
+		printk(KERN_ALERT "rcu-torture types:");
+		for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
+			printk(KERN_ALERT " %s", torture_ops[i]->name);
+		printk(KERN_ALERT "\n");
 		mutex_unlock(&fullstop_mutex);
 		return -EINVAL;
 	}

[tip:core/rcu] rcu: Do tiny cleanups in rcutiny

[tip-bot for Ingo Molnar]

Commit-ID:  4ce5b90340879ce93d169b7b523c2cbbe7c45843
Gitweb:     http://git.kernel.org/tip/4ce5b90340879ce93d169b7b523c2cbbe7c45843
Author:     Ingo Molnar <mingo@elte.hu>
AuthorDate: Mon, 26 Oct 2009 07:55:55 +0100
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 26 Oct 2009 09:40:40 +0100

rcu: Do tiny cleanups in rcutiny

No change in functionality - just straighten out a few small
stylistic details.

Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: avi@redhat.com
Cc: mtosatti@redhat.com
LKML-Reference: <12565226351355-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 include/linux/rcutiny.h |    6 +---
 kernel/rcutiny.c        |   49 ++++++++++++++++++++++------------------------
 2 files changed, 25 insertions(+), 30 deletions(-)

diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 891073c..2c1fe83 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -20,9 +20,8 @@
  * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
  *
  * For detailed explanation of Read-Copy Update mechanism see -
- * 		Documentation/RCU
+ *		Documentation/RCU
  */
-
 #ifndef __LINUX_TINY_H
 #define __LINUX_TINY_H
 
@@ -70,8 +69,7 @@ static inline void synchronize_rcu_bh_expedited(void)
 }
 
 struct notifier_block;
-extern int rcu_cpu_notify(struct notifier_block *self,
-			  unsigned long action, void *hcpu);
+extern int rcu_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu);
 
 #ifdef CONFIG_NO_HZ
 
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index 0b54efd..b33ec3a 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -20,22 +20,21 @@
  * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
  *
  * For detailed explanation of Read-Copy Update mechanism see -
- * 		Documentation/RCU
+ *		Documentation/RCU
  */
-
-#include <linux/types.h>
-#include <linux/kernel.h>
-#include <linux/init.h>
-#include <linux/rcupdate.h>
-#include <linux/interrupt.h>
-#include <linux/sched.h>
-#include <linux/module.h>
-#include <linux/completion.h>
 #include <linux/moduleparam.h>
+#include <linux/completion.h>
+#include <linux/interrupt.h>
 #include <linux/notifier.h>
-#include <linux/cpu.h>
+#include <linux/rcupdate.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/init.h>
 #include <linux/time.h>
+#include <linux/cpu.h>
 
 /* Global control variables for rcupdate callback mechanism. */
 struct rcu_ctrlblk {
@@ -46,14 +45,13 @@ struct rcu_ctrlblk {
 
 /* Definition for rcupdate control block. */
 static struct rcu_ctrlblk rcu_ctrlblk = {
-	.rcucblist = NULL,
-	.donetail = &rcu_ctrlblk.rcucblist,
-	.curtail = &rcu_ctrlblk.rcucblist,
+	.donetail	= &rcu_ctrlblk.rcucblist,
+	.curtail	= &rcu_ctrlblk.rcucblist,
 };
+
 static struct rcu_ctrlblk rcu_bh_ctrlblk = {
-	.rcucblist = NULL,
-	.donetail = &rcu_bh_ctrlblk.rcucblist,
-	.curtail = &rcu_bh_ctrlblk.rcucblist,
+	.donetail	= &rcu_bh_ctrlblk.rcucblist,
+	.curtail	= &rcu_bh_ctrlblk.rcucblist,
 };
 
 #ifdef CONFIG_NO_HZ
@@ -84,8 +82,8 @@ void rcu_exit_nohz(void)
 
 /*
  * Helper function for rcu_qsctr_inc() and rcu_bh_qsctr_inc().
- * Also disable irqs to avoid confusion due to interrupt handlers invoking
- * call_rcu().
+ * Also disable irqs to avoid confusion due to interrupt handlers
+ * invoking call_rcu().
  */
 static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
 {
@@ -99,6 +97,7 @@ static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
 		return 1;
 	}
 	local_irq_restore(flags);
+
 	return 0;
 }
 
@@ -143,8 +142,8 @@ void rcu_check_callbacks(int cpu, int user)
  */
 static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
 {
-	unsigned long flags;
 	struct rcu_head *next, *list;
+	unsigned long flags;
 
 	/* If no RCU callbacks ready to invoke, just return. */
 	if (&rcp->rcucblist == rcp->donetail)
@@ -182,8 +181,7 @@ static void rcu_process_callbacks(struct softirq_action *unused)
  * Null function to handle CPU being onlined.  Longer term, we want to
  * make TINY_RCU avoid using rcupdate.c, but later...
  */
-int rcu_cpu_notify(struct notifier_block *self,
-		   unsigned long action, void *hcpu)
+int rcu_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
 {
 	return NOTIFY_OK;
 }
@@ -223,6 +221,7 @@ static void __call_rcu(struct rcu_head *head,
 
 	head->func = func;
 	head->next = NULL;
+
 	local_irq_save(flags);
 	*rcp->curtail = head;
 	rcp->curtail = &head->next;
@@ -234,8 +233,7 @@ static void __call_rcu(struct rcu_head *head,
  * period.  But since we have but one CPU, that would be after any
  * quiescent state.
  */
-void call_rcu(struct rcu_head *head,
-	      void (*func)(struct rcu_head *rcu))
+void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
 {
 	__call_rcu(head, func, &rcu_ctrlblk);
 }
@@ -245,8 +243,7 @@ EXPORT_SYMBOL_GPL(call_rcu);
  * Post an RCU bottom-half callback to be invoked after any subsequent
  * quiescent state.
  */
-void call_rcu_bh(struct rcu_head *head,
-		 void (*func)(struct rcu_head *rcu))
+void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
 {
 	__call_rcu(head, func, &rcu_bh_ctrlblk);
 }

Re: [tip:core/rcu] rcu: Do tiny cleanups in rcutiny

[Paul E. McKenney]

On Mon, Oct 26, 2009 at 11:37:58AM +0000, tip-bot for Ingo Molnar wrote:
> Commit-ID:  4ce5b90340879ce93d169b7b523c2cbbe7c45843
> Gitweb:     http://git.kernel.org/tip/4ce5b90340879ce93d169b7b523c2cbbe7c45843
> Author:     Ingo Molnar <mingo@elte.hu>
> AuthorDate: Mon, 26 Oct 2009 07:55:55 +0100
> Committer:  Ingo Molnar <mingo@elte.hu>
> CommitDate: Mon, 26 Oct 2009 09:40:40 +0100
> 
> rcu: Do tiny cleanups in rcutiny
> 
> No change in functionality - just straighten out a few small
> stylistic details.

These all look good to me.

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Cc: David Howells <dhowells@redhat.com>
> Cc: Josh Triplett <josh@joshtriplett.org>
> Cc: laijs@cn.fujitsu.com
> Cc: dipankar@in.ibm.com
> Cc: mathieu.desnoyers@polymtl.ca
> Cc: dvhltc@us.ibm.com
> Cc: niv@us.ibm.com
> Cc: peterz@infradead.org
> Cc: rostedt@goodmis.org
> Cc: Valdis.Kletnieks@vt.edu
> Cc: avi@redhat.com
> Cc: mtosatti@redhat.com
> LKML-Reference: <12565226351355-git-send-email->
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
> ---
>  include/linux/rcutiny.h |    6 +---
>  kernel/rcutiny.c        |   49 ++++++++++++++++++++++------------------------
>  2 files changed, 25 insertions(+), 30 deletions(-)
> 
> diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
> index 891073c..2c1fe83 100644
> --- a/include/linux/rcutiny.h
> +++ b/include/linux/rcutiny.h
> @@ -20,9 +20,8 @@
>   * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>   *
>   * For detailed explanation of Read-Copy Update mechanism see -
> - * 		Documentation/RCU
> + *		Documentation/RCU
>   */
> -
>  #ifndef __LINUX_TINY_H
>  #define __LINUX_TINY_H
> 
> @@ -70,8 +69,7 @@ static inline void synchronize_rcu_bh_expedited(void)
>  }
> 
>  struct notifier_block;
> -extern int rcu_cpu_notify(struct notifier_block *self,
> -			  unsigned long action, void *hcpu);
> +extern int rcu_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu);
> 
>  #ifdef CONFIG_NO_HZ
> 
> diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
> index 0b54efd..b33ec3a 100644
> --- a/kernel/rcutiny.c
> +++ b/kernel/rcutiny.c
> @@ -20,22 +20,21 @@
>   * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>   *
>   * For detailed explanation of Read-Copy Update mechanism see -
> - * 		Documentation/RCU
> + *		Documentation/RCU
>   */
> -
> -#include <linux/types.h>
> -#include <linux/kernel.h>
> -#include <linux/init.h>
> -#include <linux/rcupdate.h>
> -#include <linux/interrupt.h>
> -#include <linux/sched.h>
> -#include <linux/module.h>
> -#include <linux/completion.h>
>  #include <linux/moduleparam.h>
> +#include <linux/completion.h>
> +#include <linux/interrupt.h>
>  #include <linux/notifier.h>
> -#include <linux/cpu.h>
> +#include <linux/rcupdate.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
>  #include <linux/mutex.h>
> +#include <linux/sched.h>
> +#include <linux/types.h>
> +#include <linux/init.h>
>  #include <linux/time.h>
> +#include <linux/cpu.h>
> 
>  /* Global control variables for rcupdate callback mechanism. */
>  struct rcu_ctrlblk {
> @@ -46,14 +45,13 @@ struct rcu_ctrlblk {
> 
>  /* Definition for rcupdate control block. */
>  static struct rcu_ctrlblk rcu_ctrlblk = {
> -	.rcucblist = NULL,
> -	.donetail = &rcu_ctrlblk.rcucblist,
> -	.curtail = &rcu_ctrlblk.rcucblist,
> +	.donetail	= &rcu_ctrlblk.rcucblist,
> +	.curtail	= &rcu_ctrlblk.rcucblist,
>  };
> +
>  static struct rcu_ctrlblk rcu_bh_ctrlblk = {
> -	.rcucblist = NULL,
> -	.donetail = &rcu_bh_ctrlblk.rcucblist,
> -	.curtail = &rcu_bh_ctrlblk.rcucblist,
> +	.donetail	= &rcu_bh_ctrlblk.rcucblist,
> +	.curtail	= &rcu_bh_ctrlblk.rcucblist,
>  };
> 
>  #ifdef CONFIG_NO_HZ
> @@ -84,8 +82,8 @@ void rcu_exit_nohz(void)
> 
>  /*
>   * Helper function for rcu_qsctr_inc() and rcu_bh_qsctr_inc().
> - * Also disable irqs to avoid confusion due to interrupt handlers invoking
> - * call_rcu().
> + * Also disable irqs to avoid confusion due to interrupt handlers
> + * invoking call_rcu().
>   */
>  static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
>  {
> @@ -99,6 +97,7 @@ static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
>  		return 1;
>  	}
>  	local_irq_restore(flags);
> +
>  	return 0;
>  }
> 
> @@ -143,8 +142,8 @@ void rcu_check_callbacks(int cpu, int user)
>   */
>  static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
>  {
> -	unsigned long flags;
>  	struct rcu_head *next, *list;
> +	unsigned long flags;
> 
>  	/* If no RCU callbacks ready to invoke, just return. */
>  	if (&rcp->rcucblist == rcp->donetail)
> @@ -182,8 +181,7 @@ static void rcu_process_callbacks(struct softirq_action *unused)
>   * Null function to handle CPU being onlined.  Longer term, we want to
>   * make TINY_RCU avoid using rcupdate.c, but later...
>   */
> -int rcu_cpu_notify(struct notifier_block *self,
> -		   unsigned long action, void *hcpu)
> +int rcu_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
>  {
>  	return NOTIFY_OK;
>  }
> @@ -223,6 +221,7 @@ static void __call_rcu(struct rcu_head *head,
> 
>  	head->func = func;
>  	head->next = NULL;
> +
>  	local_irq_save(flags);
>  	*rcp->curtail = head;
>  	rcp->curtail = &head->next;
> @@ -234,8 +233,7 @@ static void __call_rcu(struct rcu_head *head,
>   * period.  But since we have but one CPU, that would be after any
>   * quiescent state.
>   */
> -void call_rcu(struct rcu_head *head,
> -	      void (*func)(struct rcu_head *rcu))
> +void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
>  {
>  	__call_rcu(head, func, &rcu_ctrlblk);
>  }
> @@ -245,8 +243,7 @@ EXPORT_SYMBOL_GPL(call_rcu);
>   * Post an RCU bottom-half callback to be invoked after any subsequent
>   * quiescent state.
>   */
> -void call_rcu_bh(struct rcu_head *head,
> -		 void (*func)(struct rcu_head *rcu))
> +void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
>  {
>  	__call_rcu(head, func, &rcu_bh_ctrlblk);
>  }
> --
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Re: [PATCH tip/core/rcu 6/6] rcu: Simplify creating of lockdep class for root rcu_node

[Paul E. McKenney]

On Mon, Oct 26, 2009 at 04:34:10PM +0800, Lai Jiangshan wrote:
> Paul E. McKenney wrote:
> > diff --git a/kernel/rcutree.h b/kernel/rcutree.h
> > index 599161f..e091b30 100644
> > --- a/kernel/rcutree.h
> > +++ b/kernel/rcutree.h
> > @@ -296,6 +296,8 @@ DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
> >  
> >  #else /* #ifdef RCU_TREE_NONCORE */
> >  
> > +static struct lock_class_key rcu_root_class;
> > +
> 
> I think this line needs to be moved into rcutree.c.

Good point, I will submit a cleanup patch.

> >  /* Forward declarations for rcutree_plugin.h */
> >  static inline void rcu_bootup_announce(void);
> >  long rcu_batches_completed(void);
> 
> For all 6 patches:
> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>

Thank you!!!

							Thanx, Paul

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Re: [PATCH tip/core/rcu 6/6] rcu: Simplify creating of lockdep class for root rcu_node

[Paul E. McKenney]

On Mon, Oct 26, 2009 at 07:50:07AM +0100, Ingo Molnar wrote:
> 
> * Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
> 
> > From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > 
> > Use lockdep_set_class() to simplify the code and to avoid any additional
> > overhead in the !LOCKDEP case.
> > 
> > Signed-off-by: Peter Zijlstra <peterz@infradead.org>
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> 
> This signoff order is wrong - first signoff line must be the author of 
> the patch. (which is a pretty general rule with only rare exceptions) 
> 
> This patch was from Peter originally, right? In such cases please add:
> 
>   From: Peter Zijlstra <peterz@infradead.org>
> 
> To the head of the patch. Or, if Peter acked it, add:
> 
>   Acked-by: Peter Zijlstra <peterz@infradead.org>
> 
> SOB lines are strictly only added by people who send patches to you - 
> i.e. it records the patch handling pathway.

I will resubmit with this fixed up, apologies for my confusion.

							Thanx, Paul