[PATCH RFC 3/9] RCU: Preemptible RCU

Paul E. McKenney
2007-09-10T18:34:28Z

Work in progress, not for inclusion.

This patch implements a new version of RCU which allows its read-side
critical sections to be preempted. It uses a set of counter pairs
to keep track of the read-side critical sections and flips them
when all tasks exit read-side critical section. The details
of this implementation can be found in this paper -

http://www.rdrop.com/users/paulmck/RCU/OLSrtRCU.2006.08.11a.pdf

This patch was developed as a part of the -rt kernel development and
meant to provide better latencies when read-side critical sections of
RCU don't disable preemption. As a consequence of keeping track of RCU
readers, the readers have a slight overhead (optimizations in the paper).
This implementation co-exists with the "classic" RCU implementations
and can be switched to at compiler.

Also includes RCU tracing summarized in debugfs and RCU_SOFTIRQ for
the preemptible variant of RCU.

Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org> (for RCU_SOFTIRQ)
Signed-off-by: Paul McKenney <paulmck@us.ibm.com>
---

include/linux/interrupt.h | 1
include/linux/rcuclassic.h | 2
include/linux/rcupdate.h | 7
include/linux/rcupreempt.h | 78 +++
include/linux/rcupreempt_trace.h | 100 +++++
include/linux/sched.h | 5
kernel/Kconfig.preempt | 38 +
kernel/Makefile | 7
kernel/fork.c | 4
kernel/rcupreempt.c | 767 +++++++++++++++++++++++++++++++++++++++
kernel/rcupreempt_trace.c | 330 ++++++++++++++++
11 files changed, 1336 insertions(+), 3 deletions(-)

diff -urpNa -X dontdiff linux-2.6.22-b-fixbarriers/include/linux/interrupt.h linux-2.6.22-c-preemptrcu/include/linux/interrupt.h
--- linux-2.6.22-b-fixbarriers/include/linux/interrupt.h 2007-07-08 16:32:17.000000000 -0700
+++ linux-2.6.22-c-preemptrcu/include/linux/interrupt.h 2007-08-22 15:21:06.000000000 -0700
@@ -269,6 +269,7 @@ enum
#ifdef CONFIG_HIGH_RES_TIMERS
HRTIMER_SOFTIRQ,
#endif
+ RCU_SOFTIRQ, /* Preferable RCU should always be the last softirq */
};

/* softirq mask and active fields moved to irq_cpustat_t in
diff -urpNa -X dontdiff linux-2.6.22-b-fixbarriers/include/linux/rcuclassic.h linux-2.6.22-c-preemptrcu/include/linux/rcuclassic.h
--- linux-2.6.22-b-fixbarriers/include/linux/rcuclassic.h 2007-08-22 14:42:23.000000000 -0700
+++ linux-2.6.22-c-preemptrcu/include/linux/rcuclassic.h 2007-08-22 15:21:06.000000000 -0700
@@ -142,8 +142,6 @@ extern int rcu_needs_cpu(int cpu);
extern void __rcu_init(void);
extern void rcu_check_callbacks(int cpu, int user);
extern void rcu_restart_cpu(int cpu);
-extern long rcu_batches_completed(void);
-extern long rcu_batches_completed_bh(void);

#endif /* __KERNEL__ */
#endif /* __LINUX_RCUCLASSIC_H */
diff -urpNa -X dontdiff linux-2.6.22-b-fixbarriers/include/linux/rcupdate.h linux-2.6.22-c-preemptrcu/include/linux/rcupdate.h
--- linux-2.6.22-b-fixbarriers/include/linux/rcupdate.h 2007-07-19 14:02:36.000000000 -0700
+++ linux-2.6.22-c-preemptrcu/include/linux/rcupdate.h 2007-08-22 15:21:06.000000000 -0700
@@ -52,7 +52,11 @@ struct rcu_head {
void (*func)(struct rcu_head *head);
};

+#ifdef CONFIG_CLASSIC_RCU
#include <linux/rcuclassic.h>
+#else /* #ifdef CONFIG_CLASSIC_RCU */
+#include <linux/rcupreempt.h>
+#endif /* #else #ifdef CONFIG_CLASSIC_RCU */

#define RCU_HEAD_INIT { .next = NULL, .func = NULL }
#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT
@@ -218,10 +222,13 @@ extern void FASTCALL(call_rcu_bh(struct
/* Exported common interfaces */
extern void synchronize_rcu(void);
extern void rcu_barrier(void);
+extern long rcu_batches_completed(void);
+extern long rcu_batches_completed_bh(void);

/* Internal to kernel */
extern void rcu_init(void);
extern void rcu_check_callbacks(int cpu, int user);
+extern int rcu_needs_cpu(int cpu);

#endif /* __KERNEL__ */
#endif /* __LINUX_RCUPDATE_H */
diff -urpNa -X dontdiff linux-2.6.22-b-fixbarriers/include/linux/rcupreempt.h linux-2.6.22-c-preemptrcu/include/linux/rcupreempt.h
--- linux-2.6.22-b-fixbarriers/include/linux/rcupreempt.h 1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.22-c-preemptrcu/include/linux/rcupreempt.h 2007-08-22 15:21:06.000000000 -0700
@@ -0,0 +1,78 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion (RT implementation)
+ *
+ * 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 (C) IBM Corporation, 2006
+ *
+ * Author: Paul McKenney <paulmck@us.ibm.com>
+ *
+ * Based on the original work by Paul McKenney <paul.mckenney@us.ibm.com>
+ * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
+ * Papers:
+ * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
+ * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * Documentation/RCU
+ *
+ */
+
+#ifndef __LINUX_RCUPREEMPT_H
+#define __LINUX_RCUPREEMPT_H
+
+#ifdef __KERNEL__
+
+#include <linux/cache.h>
+#include <linux/spinlock.h>
+#include <linux/threads.h>
+#include <linux/percpu.h>
+#include <linux/cpumask.h>
+#include <linux/seqlock.h>
+
+#define rcu_qsctr_inc(cpu)
+#define rcu_bh_qsctr_inc(cpu)
+#define call_rcu_bh(head, rcu) call_rcu(head, rcu)
+
+extern void __rcu_read_lock(void);
+extern void __rcu_read_unlock(void);
+extern int rcu_pending(int cpu);
+extern int rcu_needs_cpu(int cpu);
+
+#define __rcu_read_lock_bh() { rcu_read_lock(); local_bh_disable(); }
+#define __rcu_read_unlock_bh() { local_bh_enable(); rcu_read_unlock(); }
+
+#define __rcu_read_lock_nesting() (current->rcu_read_lock_nesting)
+
+extern void __synchronize_sched(void);
+
+extern void __rcu_init(void);
+extern void rcu_check_callbacks(int cpu, int user);
+extern void rcu_restart_cpu(int cpu);
+
+#ifdef CONFIG_RCU_TRACE
+struct rcupreempt_trace;
+extern int *rcupreempt_flipctr(int cpu);
+extern long rcupreempt_data_completed(void);
+extern int rcupreempt_flip_flag(int cpu);
+extern int rcupreempt_mb_flag(int cpu);
+extern char *rcupreempt_try_flip_state_name(void);
+extern struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu);
+#endif
+
+struct softirq_action;
+
+#endif /* __KERNEL__ */
+#endif /* __LINUX_RCUPREEMPT_H */
diff -urpNa -X dontdiff linux-2.6.22-b-fixbarriers/include/linux/rcupreempt_trace.h linux-2.6.22-c-preemptrcu/include/linux/rcupreempt_trace.h
--- linux-2.6.22-b-fixbarriers/include/linux/rcupreempt_trace.h 1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.22-c-preemptrcu/include/linux/rcupreempt_trace.h 2007-08-22 15:21:06.000000000 -0700
@@ -0,0 +1,100 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion (RT implementation)
+ *
+ * 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 (C) IBM Corporation, 2006
+ *
+ * Author: Paul McKenney <paulmck@us.ibm.com>
+ *
+ * Based on the original work by Paul McKenney <paul.mckenney@us.ibm.com>
+ * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
+ * Papers:
+ * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
+ * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * http://lse.sourceforge.net/locking/rcupdate.html
+ *
+ */
+
+#ifndef __LINUX_RCUPREEMPT_TRACE_H
+#define __LINUX_RCUPREEMPT_TRACE_H
+
+#ifdef __KERNEL__
+#include <linux/types.h>
+#include <linux/kernel.h>
+
+#include <asm/atomic.h>
+
+/*
+ * PREEMPT_RCU data structures.
+ */
+
+struct rcupreempt_trace {
+ long next_length;
+ long next_add;
+ long wait_length;
+ long wait_add;
+ long done_length;
+ long done_add;
+ long done_remove;
+ atomic_t done_invoked;
+ long rcu_check_callbacks;
+ atomic_t rcu_try_flip_1;
+ atomic_t rcu_try_flip_e1;
+ long rcu_try_flip_i1;
+ long rcu_try_flip_ie1;
+ long rcu_try_flip_g1;
+ long rcu_try_flip_a1;
+ long rcu_try_flip_ae1;
+ long rcu_try_flip_a2;
+ long rcu_try_flip_z1;
+ long rcu_try_flip_ze1;
+ long rcu_try_flip_z2;
+ long rcu_try_flip_m1;
+ long rcu_try_flip_me1;
+ long rcu_try_flip_m2;
+};
+
+#ifdef CONFIG_RCU_TRACE
+#define RCU_TRACE(fn, arg) fn(arg);
+#else
+#define RCU_TRACE(fn, arg)
+#endif
+
+extern void rcupreempt_trace_move2done(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_move2wait(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_1(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_e1(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_i1(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_ie1(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_g1(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_a1(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_ae1(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_a2(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_z1(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_ze1(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_z2(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_m1(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_me1(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_try_flip_m2(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_check_callbacks(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_done_remove(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_invoke(struct rcupreempt_trace *trace);
+extern void rcupreempt_trace_next_add(struct rcupreempt_trace *trace);
+
+#endif /* __KERNEL__ */
+#endif /* __LINUX_RCUPREEMPT_TRACE_H */
diff -urpNa -X dontdiff linux-2.6.22-b-fixbarriers/include/linux/sched.h linux-2.6.22-c-preemptrcu/include/linux/sched.h
--- linux-2.6.22-b-fixbarriers/include/linux/sched.h 2007-07-08 16:32:17.000000000 -0700
+++ linux-2.6.22-c-preemptrcu/include/linux/sched.h 2007-08-22 15:21:06.000000000 -0700
@@ -850,6 +850,11 @@ struct task_struct {
cpumask_t cpus_allowed;
unsigned int time_slice, first_time_slice;

+#ifdef CONFIG_PREEMPT_RCU
+ int rcu_read_lock_nesting;
+ int rcu_flipctr_idx;
+#endif /* #ifdef CONFIG_PREEMPT_RCU */
+
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
struct sched_info sched_info;
#endif
diff -urpNa -X dontdiff linux-2.6.22-b-fixbarriers/kernel/fork.c linux-2.6.22-c-preemptrcu/kernel/fork.c
--- linux-2.6.22-b-fixbarriers/kernel/fork.c 2007-07-08 16:32:17.000000000 -0700
+++ linux-2.6.22-c-preemptrcu/kernel/fork.c 2007-08-22 15:21:06.000000000 -0700
@@ -1032,6 +1032,10 @@ static struct task_struct *copy_process(

INIT_LIST_HEAD(&p->children);
INIT_LIST_HEAD(&p->sibling);
+#ifdef CONFIG_PREEMPT_RCU
+ p->rcu_read_lock_nesting = 0;
+ p->rcu_flipctr_idx = 0;
+#endif /* #ifdef CONFIG_PREEMPT_RCU */
p->vfork_done = NULL;
spin_lock_init(&p->alloc_lock);

diff -urpNa -X dontdiff linux-2.6.22-b-fixbarriers/kernel/Kconfig.preempt linux-2.6.22-c-preemptrcu/kernel/Kconfig.preempt
--- linux-2.6.22-b-fixbarriers/kernel/Kconfig.preempt 2007-07-08 16:32:17.000000000 -0700
+++ linux-2.6.22-c-preemptrcu/kernel/Kconfig.preempt 2007-08-22 15:21:06.000000000 -0700
@@ -63,3 +63,41 @@ config PREEMPT_BKL
Say Y here if you are building a kernel for a desktop system.
Say N if you are unsure.

+choice
+ prompt "RCU implementation type:"
+ default CLASSIC_RCU
+
+config CLASSIC_RCU
+ bool "Classic RCU"
+ help
+ This option selects the classic RCU implementation that is
+ designed for best read-side performance on non-realtime
+ systems.
+
+ Say Y if you are unsure.
+
+config PREEMPT_RCU
+ bool "Preemptible RCU"
+ depends on PREEMPT
+ help
+ This option reduces the latency of the kernel by making certain
+ RCU sections preemptible. Normally RCU code is non-preemptible, if
+ this option is selected then read-only RCU sections become
+ preemptible. This helps latency, but may expose bugs due to
+ now-naive assumptions about each RCU read-side critical section
+ remaining on a given CPU through its execution.
+
+ Say N if you are unsure.
+
+endchoice
+
+config RCU_TRACE
+ bool "Enable tracing for RCU - currently stats in debugfs"
+ select DEBUG_FS
+ default y
+ help
+ This option provides tracing in RCU which presents stats
+ in debugfs for debugging RCU implementation.
+
+ Say Y here if you want to enable RCU tracing
+ Say N if you are unsure.
diff -urpNa -X dontdiff linux-2.6.22-b-fixbarriers/kernel/Makefile linux-2.6.22-c-preemptrcu/kernel/Makefile
--- linux-2.6.22-b-fixbarriers/kernel/Makefile 2007-07-19 12:16:03.000000000 -0700
+++ linux-2.6.22-c-preemptrcu/kernel/Makefile 2007-08-22 15:21:06.000000000 -0700
@@ -6,7 +6,7 @@ obj-y = sched.o fork.o exec_domain.o
exit.o itimer.o time.o softirq.o resource.o \
sysctl.o capability.o ptrace.o timer.o user.o \
signal.o sys.o kmod.o workqueue.o pid.o \
- rcupdate.o rcuclassic.o extable.o params.o posix-timers.o \
+ rcupdate.o extable.o params.o posix-timers.o \
kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
hrtimer.o rwsem.o latency.o nsproxy.o srcu.o die_notifier.o

@@ -46,6 +46,11 @@ obj-$(CONFIG_DETECT_SOFTLOCKUP) += softl
obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
obj-$(CONFIG_SECCOMP) += seccomp.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
+obj-$(CONFIG_CLASSIC_RCU) += rcuclassic.o
+obj-$(CONFIG_PREEMPT_RCU) += rcupreempt.o
+ifeq ($(CONFIG_PREEMPT_RCU),y)
+obj-$(CONFIG_RCU_TRACE) += rcupreempt_trace.o
+endif
obj-$(CONFIG_RELAY) += relay.o
obj-$(CONFIG_SYSCTL) += utsname_sysctl.o
obj-$(CONFIG_UTS_NS) += utsname.o
diff -urpNa -X dontdiff linux-2.6.22-b-fixbarriers/kernel/rcupreempt.c linux-2.6.22-c-preemptrcu/kernel/rcupreempt.c
--- linux-2.6.22-b-fixbarriers/kernel/rcupreempt.c 1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.22-c-preemptrcu/kernel/rcupreempt.c 2007-08-22 15:35:19.000000000 -0700
@@ -0,0 +1,767 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion, realtime implementation
+ *
+ * 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, 2006
+ *
+ * Authors: Paul E. McKenney <paulmck@us.ibm.com>
+ * With thanks to Esben Nielsen, Bill Huey, and Ingo Molnar
+ * for pushing me away from locks and towards counters, and
+ * to Suparna Bhattacharya for pushing me completely away
+ * from atomic instructions on the read side.
+ *
+ * Papers: http://www.rdrop.com/users/paulmck/RCU
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * Documentation/RCU/ *.txt
+ *
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <asm/atomic.h>
+#include <linux/bitops.h>
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/rcupdate.h>
+#include <linux/cpu.h>
+#include <linux/random.h>
+#include <linux/delay.h>
+#include <linux/byteorder/swabb.h>
+#include <linux/cpumask.h>
+#include <linux/rcupreempt_trace.h>
+
+/*
+ * PREEMPT_RCU data structures.
+ */
+
+#define GP_STAGES 4
+struct rcu_data {
+ spinlock_t lock; /* Protect rcu_data fields. */
+ long completed; /* Number of last completed batch. */
+ int waitlistcount;
+ struct tasklet_struct rcu_tasklet;
+ struct rcu_head *nextlist;
+ struct rcu_head **nexttail;
+ struct rcu_head *waitlist[GP_STAGES];
+ struct rcu_head **waittail[GP_STAGES];
+ struct rcu_head *donelist;
+ struct rcu_head **donetail;
+#ifdef CONFIG_RCU_TRACE
+ struct rcupreempt_trace trace;
+#endif /* #ifdef CONFIG_RCU_TRACE */
+};
+struct rcu_ctrlblk {
+ spinlock_t fliplock; /* Protect state-machine transitions. */
+ long completed; /* Number of last completed batch. */
+};
+static DEFINE_PER_CPU(struct rcu_data, rcu_data);
+static struct rcu_ctrlblk rcu_ctrlblk = {
+ .fliplock = SPIN_LOCK_UNLOCKED,
+ .completed = 0,
+};
+static DEFINE_PER_CPU(int [2], rcu_flipctr) = { 0, 0 };
+
+/*
+ * States for rcu_try_flip() and friends.
+ */
+
+enum rcu_try_flip_states {
+ rcu_try_flip_idle_state, /* "I" */
+ rcu_try_flip_waitack_state, /* "A" */
+ rcu_try_flip_waitzero_state, /* "Z" */
+ rcu_try_flip_waitmb_state /* "M" */
+};
+static enum rcu_try_flip_states rcu_try_flip_state = rcu_try_flip_idle_state;
+#ifdef CONFIG_RCU_TRACE
+static char *rcu_try_flip_state_names[] =
+ { "idle", "waitack", "waitzero", "waitmb" };
+#endif /* #ifdef CONFIG_RCU_TRACE */
+
+/*
+ * Enum and per-CPU flag to determine when each CPU has seen
+ * the most recent counter flip.
+ */
+
+enum rcu_flip_flag_values {
+ rcu_flip_seen, /* Steady/initial state, last flip seen. */
+ /* Only GP detector can update. */
+ rcu_flipped /* Flip just completed, need confirmation. */
+ /* Only corresponding CPU can update. */
+};
+static DEFINE_PER_CPU(enum rcu_flip_flag_values, rcu_flip_flag) = rcu_flip_seen;
+
+/*
+ * Enum and per-CPU flag to determine when each CPU has executed the
+ * needed memory barrier to fence in memory references from its last RCU
+ * read-side critical section in the just-completed grace period.
+ */
+
+enum rcu_mb_flag_values {
+ rcu_mb_done, /* Steady/initial state, no mb()s required. */
+ /* Only GP detector can update. */
+ rcu_mb_needed /* Flip just completed, need an mb(). */
+ /* Only corresponding CPU can update. */
+};
+static DEFINE_PER_CPU(enum rcu_mb_flag_values, rcu_mb_flag) = rcu_mb_done;
+
+/*
+ * Macro that prevents the compiler from reordering accesses, but does
+ * absolutely -nothing- to prevent CPUs from reordering. This is used
+ * only to mediate communication between mainline code and hardware
+ * interrupt and NMI handlers.
+ */
+#define ORDERED_WRT_IRQ(x) (*(volatile typeof(x) *)&(x))
+
+/*
+ * RCU_DATA_ME: find the current CPU's rcu_data structure.
+ * RCU_DATA_CPU: find the specified CPU's rcu_data structure.
+ */
+#define RCU_DATA_ME() (&__get_cpu_var(rcu_data))
+#define RCU_DATA_CPU(cpu) (&per_cpu(rcu_data, cpu))
+
+/*
+ * Helper macro for tracing when the appropriate rcu_data is not
+ * cached in a local variable, but where the CPU number is so cached.
+ */
+#define RCU_TRACE_CPU(f, cpu) RCU_TRACE(f, &(RCU_DATA_CPU(cpu)->trace));
+
+/*
+ * Helper macro for tracing when the appropriate rcu_data is not
+ * cached in a local variable.
+ */
+#define RCU_TRACE_ME(f) RCU_TRACE(f, &(RCU_DATA_ME()->trace));
+
+/*
+ * Helper macro for tracing when the appropriate rcu_data is pointed
+ * to by a local variable.
+ */
+#define RCU_TRACE_RDP(f, rdp) RCU_TRACE(f, &((rdp)->trace));
+
+/*
+ * Return the number of RCU batches processed thus far. Useful
+ * for debug and statistics.
+ */
+long rcu_batches_completed(void)
+{
+ return rcu_ctrlblk.completed;
+}
+EXPORT_SYMBOL_GPL(rcu_batches_completed);
+
+/*
+ * Return the number of RCU batches processed thus far. Useful for debug
+ * and statistics. The _bh variant is identical to straight RCU.
+ */
+long rcu_batches_completed_bh(void)
+{
+ return rcu_ctrlblk.completed;
+}
+EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
+
+void __rcu_read_lock(void)
+{
+ int idx;
+ struct task_struct *me = current;
+ int nesting;
+
+ nesting = ORDERED_WRT_IRQ(me->rcu_read_lock_nesting);
+ if (nesting != 0) {
+
+ /* An earlier rcu_read_lock() covers us, just count it. */
+
+ me->rcu_read_lock_nesting = nesting + 1;
+
+ } else {
+ unsigned long oldirq;
+
+ /*
+ * Disable local interrupts to prevent the grace-period
+ * detection state machine from seeing us half-done.
+ * NMIs can still occur, of course, and might themselves
+ * contain rcu_read_lock().
+ */
+
+ local_irq_save(oldirq);
+
+ /*
+ * Outermost nesting of rcu_read_lock(), so increment
+ * the current counter for the current CPU. Use volatile
+ * casts to prevent the compiler from reordering.
+ */
+
+ idx = ORDERED_WRT_IRQ(rcu_ctrlblk.completed) & 0x1;
+ smp_read_barrier_depends(); /* @@@@ might be unneeded */
+ ORDERED_WRT_IRQ(__get_cpu_var(rcu_flipctr)[idx])++;
+
+ /*
+ * Now that the per-CPU counter has been incremented, we
+ * are protected from races with rcu_read_lock() invoked
+ * from NMI handlers on this CPU. We can therefore safely
+ * increment the nesting counter, relieving further NMIs
+ * of the need to increment the per-CPU counter.
+ */
+
+ ORDERED_WRT_IRQ(me->rcu_read_lock_nesting) = nesting + 1;
+
+ /*
+ * Now that we have preventing any NMIs from storing
+ * to the ->rcu_flipctr_idx, we can safely use it to
+ * remember which counter to decrement in the matching
+ * rcu_read_unlock().
+ */
+
+ ORDERED_WRT_IRQ(me->rcu_flipctr_idx) = idx;
+ local_irq_restore(oldirq);
+ }
+}
+EXPORT_SYMBOL_GPL(__rcu_read_lock);
+
+void __rcu_read_unlock(void)
+{
+ int idx;
+ struct task_struct *me = current;
+ int nesting;
+
+ nesting = ORDERED_WRT_IRQ(me->rcu_read_lock_nesting);
+ if (nesting > 1) {
+
+ /*
+ * We are still protected by the enclosing rcu_read_lock(),
+ * so simply decrement the counter.
+ */
+
+ me->rcu_read_lock_nesting = nesting - 1;
+
+ } else {
+ unsigned long oldirq;
+
+ /*
+ * Disable local interrupts to prevent the grace-period
+ * detection state machine from seeing us half-done.
+ * NMIs can still occur, of course, and might themselves
+ * contain rcu_read_lock() and rcu_read_unlock().
+ */
+
+ local_irq_save(oldirq);
+
+ /*
+ * Outermost nesting of rcu_read_unlock(), so we must
+ * decrement the current counter for the current CPU.
+ * This must be done carefully, because NMIs can
+ * occur at any point in this code, and any rcu_read_lock()
+ * and rcu_read_unlock() pairs in the NMI handlers
+ * must interact non-destructively with this code.
+ * Lots of volatile casts, and -very- careful ordering.
+ *
+ * Changes to this code, including this one, must be
+ * inspected, validated, and tested extremely carefully!!!
+ */
+
+ /*
+ * First, pick up the index. Enforce ordering for
+ * DEC Alpha.
+ */
+
+ idx = ORDERED_WRT_IRQ(me->rcu_flipctr_idx);
+ smp_read_barrier_depends(); /* @@@ Needed??? */
+
+ /*
+ * Now that we have fetched the counter index, it is
+ * safe to decrement the per-task RCU nesting counter.
+ * After this, any interrupts or NMIs will increment and
+ * decrement the per-CPU counters.
+ */
+ ORDERED_WRT_IRQ(me->rcu_read_lock_nesting) = nesting - 1;
+
+ /*
+ * It is now safe to decrement this task's nesting count.
+ * NMIs that occur after this statement will route their
+ * rcu_read_lock() calls through this "else" clause, and
+ * will thus start incrementing the per-CPU coutner on
+ * their own. They will also clobber ->rcu_flipctr_idx,
+ * but that is OK, since we have already fetched it.
+ */
+
+ ORDERED_WRT_IRQ(__get_cpu_var(rcu_flipctr)[idx])--;
+ local_irq_restore(oldirq);
+ }
+}
+EXPORT_SYMBOL_GPL(__rcu_read_unlock);
+
+/*
+ * If a global counter flip has occurred since the last time that we
+ * advanced callbacks, advance them. Hardware interrupts must be
+ * disabled when calling this function.
+ */
+static void __rcu_advance_callbacks(struct rcu_data *rdp)
+{
+ int cpu;
+ int i;
+ int wlc = 0;
+
+ if (rdp->completed != rcu_ctrlblk.completed) {
+ if (rdp->waitlist[GP_STAGES - 1] != NULL) {
+ *rdp->donetail = rdp->waitlist[GP_STAGES - 1];
+ rdp->donetail = rdp->waittail[GP_STAGES - 1];
+ RCU_TRACE_RDP(rcupreempt_trace_move2done, rdp);
+ }
+ for (i = GP_STAGES - 2; i >= 0; i--) {
+ if (rdp->waitlist[i] != NULL) {
+ rdp->waitlist[i + 1] = rdp->waitlist[i];
+ rdp->waittail[i + 1] = rdp->waittail[i];
+ wlc++;
+ } else {
+ rdp->waitlist[i + 1] = NULL;
+ rdp->waittail[i + 1] =
+ &rdp->waitlist[i + 1];
+ }
+ }
+ if (rdp->nextlist != NULL) {
+ rdp->waitlist[0] = rdp->nextlist;
+ rdp->waittail[0] = rdp->nexttail;
+ wlc++;
+ rdp->nextlist = NULL;
+ rdp->nexttail = &rdp->nextlist;
+ RCU_TRACE_RDP(rcupreempt_trace_move2wait, rdp);
+ } else {
+ rdp->waitlist[0] = NULL;
+ rdp->waittail[0] = &rdp->waitlist[0];
+ }
+ rdp->waitlistcount = wlc;
+ rdp->completed = rcu_ctrlblk.completed;
+ }
+
+ /*
+ * Check to see if this CPU needs to report that it has seen
+ * the most recent counter flip, thereby declaring that all
+ * subsequent rcu_read_lock() invocations will respect this flip.
+ */
+
+ cpu = raw_smp_processor_id();
+ if (per_cpu(rcu_flip_flag, cpu) == rcu_flipped) {
+ smp_mb(); /* Subsequent counter accesses must see new value */
+ per_cpu(rcu_flip_flag, cpu) = rcu_flip_seen;
+ smp_mb(); /* Subsequent RCU read-side critical sections */
+ /* seen -after- acknowledgement. */
+ }
+}
+
+/*
+ * Get here when RCU is idle. Decide whether we need to
+ * move out of idle state, and return non-zero if so.
+ * "Straightforward" approach for the moment, might later
+ * use callback-list lengths, grace-period duration, or
+ * some such to determine when to exit idle state.
+ * Might also need a pre-idle test that does not acquire
+ * the lock, but let's get the simple case working first...
+ */
+
+static int
+rcu_try_flip_idle(void)
+{
+ int cpu;
+
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_i1);
+ if (!rcu_pending(smp_processor_id())) {
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_ie1);
+ return 0;
+ }
+
+ /*
+ * Do the flip.
+ */
+
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_g1);
+ rcu_ctrlblk.completed++; /* stands in for rcu_try_flip_g2 */
+
+ /*
+ * Need a memory barrier so that other CPUs see the new
+ * counter value before they see the subsequent change of all
+ * the rcu_flip_flag instances to rcu_flipped.
+ */
+
+ smp_mb(); /* see above block comment. */
+
+ /* Now ask each CPU for acknowledgement of the flip. */
+
+ for_each_possible_cpu(cpu)
+ per_cpu(rcu_flip_flag, cpu) = rcu_flipped;
+
+ return 1;
+}
+
+/*
+ * Wait for CPUs to acknowledge the flip.
+ */
+
+static int
+rcu_try_flip_waitack(void)
+{
+ int cpu;
+
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_a1);
+ for_each_possible_cpu(cpu)
+ if (per_cpu(rcu_flip_flag, cpu) != rcu_flip_seen) {
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_ae1);
+ return 0;
+ }
+
+ /*
+ * Make sure our checks above don't bleed into subsequent
+ * waiting for the sum of the counters to reach zero.
+ */
+
+ smp_mb(); /* see above block comment. */
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_a2);
+ return 1;
+}
+
+/*
+ * Wait for collective ``last'' counter to reach zero,
+ * then tell all CPUs to do an end-of-grace-period memory barrier.
+ */
+
+static int
+rcu_try_flip_waitzero(void)
+{
+ int cpu;
+ int lastidx = !(rcu_ctrlblk.completed & 0x1);
+ int sum = 0;
+
+ /* Check to see if the sum of the "last" counters is zero. */
+
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_z1);
+ for_each_possible_cpu(cpu)
+ sum += per_cpu(rcu_flipctr, cpu)[lastidx];
+ if (sum != 0) {
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_ze1);
+ return 0;
+ }
+
+ smp_mb(); /* Don't call for memory barriers before we see zero. */
+
+ /* Call for a memory barrier from each CPU. */
+
+ for_each_possible_cpu(cpu)
+ per_cpu(rcu_mb_flag, cpu) = rcu_mb_needed;
+
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_z2);
+ return 1;
+}
+
+/*
+ * Wait for all CPUs to do their end-of-grace-period memory barrier.
+ * Return 0 once all CPUs have done so.
+ */
+
+static int
+rcu_try_flip_waitmb(void)
+{
+ int cpu;
+
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_m1);
+ for_each_possible_cpu(cpu)
+ if (per_cpu(rcu_mb_flag, cpu) != rcu_mb_done) {
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_me1);
+ return 0;
+ }
+
+ smp_mb(); /* Ensure that the above checks precede any following flip. */
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_m2);
+ return 1;
+}
+
+/*
+ * Attempt a single flip of the counters. Remember, a single flip does
+ * -not- constitute a grace period. Instead, the interval between
+ * at least three consecutive flips is a grace period.
+ *
+ * If anyone is nuts enough to run this CONFIG_PREEMPT_RCU implementation
+ * on a large SMP, they might want to use a hierarchical organization of
+ * the per-CPU-counter pairs.
+ */
+static void rcu_try_flip(void)
+{
+ unsigned long oldirq;
+
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_1);
+ if (unlikely(!spin_trylock_irqsave(&rcu_ctrlblk.fliplock, oldirq))) {
+ RCU_TRACE_ME(rcupreempt_trace_try_flip_e1);
+ return;
+ }
+
+ /*
+ * Take the next transition(s) through the RCU grace-period
+ * flip-counter state machine.
+ */
+
+ switch (rcu_try_flip_state) {
+ case rcu_try_flip_idle_state:
+ if (rcu_try_flip_idle())
+ rcu_try_flip_state = rcu_try_flip_waitack_state;
+ break;
+ case rcu_try_flip_waitack_state:
+ if (rcu_try_flip_waitack())
+ rcu_try_flip_state = rcu_try_flip_waitzero_state;
+ break;
+ case rcu_try_flip_waitzero_state:
+ if (rcu_try_flip_waitzero())
+ rcu_try_flip_state = rcu_try_flip_waitmb_state;
+ break;
+ case rcu_try_flip_waitmb_state:
+ if (rcu_try_flip_waitmb())
+ rcu_try_flip_state = rcu_try_flip_idle_state;
+ }
+ spin_unlock_irqrestore(&rcu_ctrlblk.fliplock, oldirq);
+}
+
+/*
+ * Check to see if this CPU needs to do a memory barrier in order to
+ * ensure that any prior RCU read-side critical sections have committed
+ * their counter manipulations and critical-section memory references
+ * before declaring the grace period to be completed.
+ */
+static void rcu_check_mb(int cpu)
+{
+ if (per_cpu(rcu_mb_flag, cpu) == rcu_mb_needed) {
+ smp_mb(); /* Ensure RCU read-side accesses are visible. */
+ per_cpu(rcu_mb_flag, cpu) = rcu_mb_done;
+ }
+}
+
+void rcu_check_callbacks(int cpu, int user)
+{
+ unsigned long oldirq;
+ struct rcu_data *rdp = RCU_DATA_CPU(cpu);
+
+ rcu_check_mb(cpu);
+ if (rcu_ctrlblk.completed == rdp->completed)
+ rcu_try_flip();
+ spin_lock_irqsave(&rdp->lock, oldirq);
+ RCU_TRACE_RDP(rcupreempt_trace_check_callbacks, rdp);
+ __rcu_advance_callbacks(rdp);
+ if (rdp->donelist == NULL) {
+ spin_unlock_irqrestore(&rdp->lock, oldirq);
+ } else {
+ spin_unlock_irqrestore(&rdp->lock, oldirq);
+ raise_softirq(RCU_SOFTIRQ);
+ }
+}
+
+/*
+ * Needed by dynticks, to make sure all RCU processing has finished
+ * when we go idle:
+ */
+void rcu_advance_callbacks(int cpu, int user)
+{
+ unsigned long oldirq;
+ struct rcu_data *rdp = RCU_DATA_CPU(cpu);
+
+ if (rcu_ctrlblk.completed == rdp->completed) {
+ rcu_try_flip();
+ if (rcu_ctrlblk.completed == rdp->completed)
+ return;
+ }
+ spin_lock_irqsave(&rdp->lock, oldirq);
+ RCU_TRACE_RDP(rcupreempt_trace_check_callbacks, rdp);
+ __rcu_advance_callbacks(rdp);
+ spin_unlock_irqrestore(&rdp->lock, oldirq);
+}
+
+static void rcu_process_callbacks(struct softirq_action *unused)
+{
+ unsigned long flags;
+ struct rcu_head *next, *list;
+ struct rcu_data *rdp = RCU_DATA_ME();
+
+ spin_lock_irqsave(&rdp->lock, flags);
+ list = rdp->donelist;
+ if (list == NULL) {
+ spin_unlock_irqrestore(&rdp->lock, flags);
+ return;
+ }
+ rdp->donelist = NULL;
+ rdp->donetail = &rdp->donelist;
+ RCU_TRACE_RDP(rcupreempt_trace_done_remove, rdp);
+ spin_unlock_irqrestore(&rdp->lock, flags);
+ while (list) {
+ next = list->next;
+ list->func(list);
+ list = next;
+ RCU_TRACE_ME(rcupreempt_trace_invoke);
+ }
+}
+
+void fastcall call_rcu(struct rcu_head *head,
+ void (*func)(struct rcu_head *rcu))
+{
+ unsigned long oldirq;
+ struct rcu_data *rdp;
+
+ head->func = func;
+ head->next = NULL;
+ local_irq_save(oldirq);
+ rdp = RCU_DATA_ME();
+ spin_lock(&rdp->lock);
+ __rcu_advance_callbacks(rdp);
+ *rdp->nexttail = head;
+ rdp->nexttail = &head->next;
+ RCU_TRACE_RDP(rcupreempt_trace_next_add, rdp);
+ spin_unlock(&rdp->lock);
+ local_irq_restore(oldirq);
+}
+EXPORT_SYMBOL_GPL(call_rcu);
+
+/*
+ * Wait until all currently running preempt_disable() code segments
+ * (including hardware-irq-disable segments) complete. Note that
+ * in -rt this does -not- necessarily result in all currently executing
+ * interrupt -handlers- having completed.
+ */
+void __synchronize_sched(void)
+{
+ cpumask_t oldmask;
+ int cpu;
+
+ if (sched_getaffinity(0, &oldmask) < 0)
+ oldmask = cpu_possible_map;
+ for_each_online_cpu(cpu) {
+ sched_setaffinity(0, cpumask_of_cpu(cpu));
+ schedule();
+ }
+ sched_setaffinity(0, oldmask);
+}
+EXPORT_SYMBOL_GPL(__synchronize_sched);
+
+/*
+ * Check to see if any future RCU-related work will need to be done
+ * by the current CPU, even if none need be done immediately, returning
+ * 1 if so. Assumes that notifiers would take care of handling any
+ * outstanding requests from the RCU core.
+ *
+ * This function is part of the RCU implementation; it is -not-
+ * an exported member of the RCU API.
+ */
+int rcu_needs_cpu(int cpu)
+{
+ struct rcu_data *rdp = RCU_DATA_CPU(cpu);
+
+ return (rdp->donelist != NULL ||
+ !!rdp->waitlistcount ||
+ rdp->nextlist != NULL);
+}
+
+int rcu_pending(int cpu)
+{
+ struct rcu_data *rdp = RCU_DATA_CPU(cpu);
+
+ /* The CPU has at least one callback queued somewhere. */
+
+ if (rdp->donelist != NULL ||
+ !!rdp->waitlistcount ||
+ rdp->nextlist != NULL)
+ return 1;
+
+ /* The RCU core needs an acknowledgement from this CPU. */
+
+ if ((per_cpu(rcu_flip_flag, cpu) == rcu_flipped) ||
+ (per_cpu(rcu_mb_flag, cpu) == rcu_mb_needed))
+ return 1;
+
+ /* This CPU has fallen behind the global grace-period number. */
+
+ if (rdp->completed != rcu_ctrlblk.completed)
+ return 1;
+
+ /* Nothing needed from this CPU. */
+
+ return 0;
+}
+
+void __init __rcu_init(void)
+{
+ int cpu;
+ int i;
+ struct rcu_data *rdp;
+
+/*&&&&*/printk(KERN_NOTICE "WARNING: experimental RCU implementation.\n");
+ for_each_possible_cpu(cpu) {
+ rdp = RCU_DATA_CPU(cpu);
+ spin_lock_init(&rdp->lock);
+ rdp->completed = 0;
+ rdp->waitlistcount = 0;
+ rdp->nextlist = NULL;
+ rdp->nexttail = &rdp->nextlist;
+ for (i = 0; i < GP_STAGES; i++) {
+ rdp->waitlist[i] = NULL;
+ rdp->waittail[i] = &rdp->waitlist[i];
+ }
+ rdp->donelist = NULL;
+ rdp->donetail = &rdp->donelist;
+ }
+ open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
+}
+
+/*
+ * Deprecated, use synchronize_rcu() or synchronize_sched() instead.
+ */
+void synchronize_kernel(void)
+{
+ synchronize_rcu();
+}
+
+#ifdef CONFIG_RCU_TRACE
+int *rcupreempt_flipctr(int cpu)
+{
+ return &per_cpu(rcu_flipctr, cpu)[0];
+}
+EXPORT_SYMBOL_GPL(rcupreempt_flipctr);
+
+int rcupreempt_flip_flag(int cpu)
+{
+ return per_cpu(rcu_flip_flag, cpu);
+}
+EXPORT_SYMBOL_GPL(rcupreempt_flip_flag);
+
+int rcupreempt_mb_flag(int cpu)
+{
+ return per_cpu(rcu_mb_flag, cpu);
+}
+EXPORT_SYMBOL_GPL(rcupreempt_mb_flag);
+
+char *rcupreempt_try_flip_state_name(void)
+{
+ return rcu_try_flip_state_names[rcu_try_flip_state];
+}
+EXPORT_SYMBOL_GPL(rcupreempt_try_flip_state_name);
+
+struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu)
+{
+ struct rcu_data *rdp = RCU_DATA_CPU(cpu);
+
+ return &rdp->trace;
+}
+EXPORT_SYMBOL_GPL(rcupreempt_trace_cpu);
+
+#endif /* #ifdef RCU_TRACE */
diff -urpNa -X dontdiff linux-2.6.22-b-fixbarriers/kernel/rcupreempt_trace.c linux-2.6.22-c-preemptrcu/kernel/rcupreempt_trace.c
--- linux-2.6.22-b-fixbarriers/kernel/rcupreempt_trace.c 1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.22-c-preemptrcu/kernel/rcupreempt_trace.c 2007-08-22 15:36:12.000000000 -0700
@@ -0,0 +1,330 @@
+/*
+ * Read-Copy Update tracing for realtime implementation
+ *
+ * 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, 2006
+ *
+ * Papers: http://www.rdrop.com/users/paulmck/RCU
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * Documentation/RCU/ *.txt
+ *
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <asm/atomic.h>
+#include <linux/bitops.h>
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/rcupdate.h>
+#include <linux/cpu.h>
+#include <linux/mutex.h>
+#include <linux/rcupreempt_trace.h>
+#include <linux/debugfs.h>
+
+static struct mutex rcupreempt_trace_mutex;
+static char *rcupreempt_trace_buf;
+#define RCUPREEMPT_TRACE_BUF_SIZE 4096
+
+void rcupreempt_trace_move2done(struct rcupreempt_trace *trace)
+{
+ trace->done_length += trace->wait_length;
+ trace->done_add += trace->wait_length;
+ trace->wait_length = 0;
+}
+void rcupreempt_trace_move2wait(struct rcupreempt_trace *trace)
+{
+ trace->wait_length += trace->next_length;
+ trace->wait_add += trace->next_length;
+ trace->next_length = 0;
+}
+void rcupreempt_trace_try_flip_1(struct rcupreempt_trace *trace)
+{
+ atomic_inc(&trace->rcu_try_flip_1);
+}
+void rcupreempt_trace_try_flip_e1(struct rcupreempt_trace *trace)
+{
+ atomic_inc(&trace->rcu_try_flip_e1);
+}
+void rcupreempt_trace_try_flip_i1(struct rcupreempt_trace *trace)
+{
+ trace->rcu_try_flip_i1++;
+}
+void rcupreempt_trace_try_flip_ie1(struct rcupreempt_trace *trace)
+{
+ trace->rcu_try_flip_ie1++;
+}
+void rcupreempt_trace_try_flip_g1(struct rcupreempt_trace *trace)
+{
+ trace->rcu_try_flip_g1++;
+}
+void rcupreempt_trace_try_flip_a1(struct rcupreempt_trace *trace)
+{
+ trace->rcu_try_flip_a1++;
+}
+void rcupreempt_trace_try_flip_ae1(struct rcupreempt_trace *trace)
+{
+ trace->rcu_try_flip_ae1++;
+}
+void rcupreempt_trace_try_flip_a2(struct rcupreempt_trace *trace)
+{
+ trace->rcu_try_flip_a2++;
+}
+void rcupreempt_trace_try_flip_z1(struct rcupreempt_trace *trace)
+{
+ trace->rcu_try_flip_z1++;
+}
+void rcupreempt_trace_try_flip_ze1(struct rcupreempt_trace *trace)
+{
+ trace->rcu_try_flip_ze1++;
+}
+void rcupreempt_trace_try_flip_z2(struct rcupreempt_trace *trace)
+{
+ trace->rcu_try_flip_z2++;
+}
+void rcupreempt_trace_try_flip_m1(struct rcupreempt_trace *trace)
+{
+ trace->rcu_try_flip_m1++;
+}
+void rcupreempt_trace_try_flip_me1(struct rcupreempt_trace *trace)
+{
+ trace->rcu_try_flip_me1++;
+}
+void rcupreempt_trace_try_flip_m2(struct rcupreempt_trace *trace)
+{
+ trace->rcu_try_flip_m2++;
+}
+void rcupreempt_trace_check_callbacks(struct rcupreempt_trace *trace)
+{
+ trace->rcu_check_callbacks++;
+}
+void rcupreempt_trace_done_remove(struct rcupreempt_trace *trace)
+{
+ trace->done_remove += trace->done_length;
+ trace->done_length = 0;
+}
+void rcupreempt_trace_invoke(struct rcupreempt_trace *trace)
+{
+ atomic_inc(&trace->done_invoked);
+}
+void rcupreempt_trace_next_add(struct rcupreempt_trace *trace)
+{
+ trace->next_add++;
+ trace->next_length++;
+}
+
+static void rcupreempt_trace_sum(struct rcupreempt_trace *sp)
+{
+ struct rcupreempt_trace *cp;
+ int cpu;
+
+ memset(sp, 0, sizeof(*sp));
+ for_each_possible_cpu(cpu) {
+ cp = rcupreempt_trace_cpu(cpu);
+ sp->next_length += cp->next_length;
+ sp->next_add += cp->next_add;
+ sp->wait_length += cp->wait_length;
+ sp->wait_add += cp->wait_add;
+ sp->done_length += cp->done_length;
+ sp->done_add += cp->done_add;
+ sp->done_remove += cp->done_remove;
+ atomic_set(&sp->done_invoked, atomic_read(&cp->done_invoked));
+ sp->rcu_check_callbacks += cp->rcu_check_callbacks;
+ atomic_set(&sp->rcu_try_flip_1,
+ atomic_read(&cp->rcu_try_flip_1));
+ atomic_set(&sp->rcu_try_flip_e1,
+ atomic_read(&cp->rcu_try_flip_e1));
+ sp->rcu_try_flip_i1 += cp->rcu_try_flip_i1;
+ sp->rcu_try_flip_ie1 += cp->rcu_try_flip_ie1;
+ sp->rcu_try_flip_g1 += cp->rcu_try_flip_g1;
+ sp->rcu_try_flip_a1 += cp->rcu_try_flip_a1;
+ sp->rcu_try_flip_ae1 += cp->rcu_try_flip_ae1;
+ sp->rcu_try_flip_a2 += cp->rcu_try_flip_a2;
+ sp->rcu_try_flip_z1 += cp->rcu_try_flip_z1;
+ sp->rcu_try_flip_ze1 += cp->rcu_try_flip_ze1;
+ sp->rcu_try_flip_z2 += cp->rcu_try_flip_z2;
+ sp->rcu_try_flip_m1 += cp->rcu_try_flip_m1;
+ sp->rcu_try_flip_me1 += cp->rcu_try_flip_me1;
+ sp->rcu_try_flip_m2 += cp->rcu_try_flip_m2;
+ }
+}
+
+static ssize_t rcustats_read(struct file *filp, char __user *buffer,
+ size_t count, loff_t *ppos)
+{
+ struct rcupreempt_trace trace;
+ ssize_t bcount;
+ int cnt = 0;
+
+ rcupreempt_trace_sum(&trace);
+ mutex_lock(&rcupreempt_trace_mutex);
+ snprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE - cnt,
+ "ggp=%ld rcc=%ld\n",
+ rcu_batches_completed(),
+ trace.rcu_check_callbacks);
+ snprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE - cnt,
+ "na=%ld nl=%ld wa=%ld wl=%ld da=%ld dl=%ld dr=%ld di=%d\n"
+ "1=%d e1=%d i1=%ld ie1=%ld g1=%ld a1=%ld ae1=%ld a2=%ld\n"
+ "z1=%ld ze1=%ld z2=%ld m1=%ld me1=%ld m2=%ld\n",
+
+ trace.next_add, trace.next_length,
+ trace.wait_add, trace.wait_length,
+ trace.done_add, trace.done_length,
+ trace.done_remove, atomic_read(&trace.done_invoked),
+ atomic_read(&trace.rcu_try_flip_1),
+ atomic_read(&trace.rcu_try_flip_e1),
+ trace.rcu_try_flip_i1, trace.rcu_try_flip_ie1,
+ trace.rcu_try_flip_g1,
+ trace.rcu_try_flip_a1, trace.rcu_try_flip_ae1,
+ trace.rcu_try_flip_a2,
+ trace.rcu_try_flip_z1, trace.rcu_try_flip_ze1,
+ trace.rcu_try_flip_z2,
+ trace.rcu_try_flip_m1, trace.rcu_try_flip_me1,
+ trace.rcu_try_flip_m2);
+ bcount = simple_read_from_buffer(buffer, count, ppos,
+ rcupreempt_trace_buf, strlen(rcupreempt_trace_buf));
+ mutex_unlock(&rcupreempt_trace_mutex);
+ return bcount;
+}
+
+static ssize_t rcugp_read(struct file *filp, char __user *buffer,
+ size_t count, loff_t *ppos)
+{
+ long oldgp = rcu_batches_completed();
+ ssize_t bcount;
+
+ mutex_lock(&rcupreempt_trace_mutex);
+ synchronize_rcu();
+ snprintf(rcupreempt_trace_buf, RCUPREEMPT_TRACE_BUF_SIZE,
+ "oldggp=%ld newggp=%ld\n", oldgp, rcu_batches_completed());
+ bcount = simple_read_from_buffer(buffer, count, ppos,
+ rcupreempt_trace_buf, strlen(rcupreempt_trace_buf));
+ mutex_unlock(&rcupreempt_trace_mutex);
+ return bcount;
+}
+
+static ssize_t rcuctrs_read(struct file *filp, char __user *buffer,
+ size_t count, loff_t *ppos)
+{
+ int cnt = 0;
+ int cpu;
+ int f = rcu_batches_completed() & 0x1;
+ ssize_t bcount;
+
+ mutex_lock(&rcupreempt_trace_mutex);
+
+ cnt += snprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE,
+ "CPU last cur F M\n");
+ for_each_online_cpu(cpu) {
+ int *flipctr = rcupreempt_flipctr(cpu);
+ cnt += snprintf(&rcupreempt_trace_buf[cnt],
+ RCUPREEMPT_TRACE_BUF_SIZE - cnt,
+ "%3d %4d %3d %d %d\n",
+ cpu,
+ flipctr[!f],
+ flipctr[f],
+ rcupreempt_flip_flag(cpu),
+ rcupreempt_mb_flag(cpu));
+ }
+ cnt += snprintf(&rcupreempt_trace_buf[cnt],
+ RCUPREEMPT_TRACE_BUF_SIZE - cnt,
+ "ggp = %ld, state = %s\n",
+ rcu_batches_completed(),
+ rcupreempt_try_flip_state_name());
+ cnt += snprintf(&rcupreempt_trace_buf[cnt],
+ RCUPREEMPT_TRACE_BUF_SIZE - cnt,
+ "\n");
+ bcount = simple_read_from_buffer(buffer, count, ppos,
+ rcupreempt_trace_buf, strlen(rcupreempt_trace_buf));
+ mutex_unlock(&rcupreempt_trace_mutex);
+ return bcount;
+}
+
+static struct file_operations rcustats_fops = {
+ .owner = THIS_MODULE,
+ .read = rcustats_read,
+};
+
+static struct file_operations rcugp_fops = {
+ .owner = THIS_MODULE,
+ .read = rcugp_read,
+};
+
+static struct file_operations rcuctrs_fops = {
+ .owner = THIS_MODULE,
+ .read = rcuctrs_read,
+};
+
+static struct dentry *rcudir, *statdir, *ctrsdir, *gpdir;
+static int rcupreempt_debugfs_init(void)
+{
+ rcudir = debugfs_create_dir("rcu", NULL);
+ if (!rcudir)
+ goto out;
+ statdir = debugfs_create_file("rcustats", 0444, rcudir,
+ NULL, &rcustats_fops);
+ if (!statdir)
+ goto free_out;
+
+ gpdir = debugfs_create_file("rcugp", 0444, rcudir, NULL, &rcugp_fops);
+ if (!gpdir)
+ goto free_out;
+
+ ctrsdir = debugfs_create_file("rcuctrs", 0444, rcudir,
+ NULL, &rcuctrs_fops);
+ if (!ctrsdir)
+ goto free_out;
+ return 0;
+free_out:
+ if (statdir)
+ debugfs_remove(statdir);
+ if (gpdir)
+ debugfs_remove(gpdir);
+ debugfs_remove(rcudir);
+out:
+ return 1;
+}
+
+static int __init rcupreempt_trace_init(void)
+{
+ mutex_init(&rcupreempt_trace_mutex);
+ rcupreempt_trace_buf = kmalloc(RCUPREEMPT_TRACE_BUF_SIZE, GFP_KERNEL);
+ if (!rcupreempt_trace_buf)
+ return 1;
+ return rcupreempt_debugfs_init();
+}
+
+static void __exit rcupreempt_trace_cleanup(void)
+{
+ debugfs_remove(statdir);
+ debugfs_remove(gpdir);
+ debugfs_remove(ctrsdir);
+ debugfs_remove(rcudir);
+ kfree(rcupreempt_trace_buf);
+}
+
+
+module_init(rcupreempt_trace_init);
+module_exit(rcupreempt_trace_cleanup);