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Preempt-RCU: implementation 

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

and the article-

	http://lwn.net/Articles/253651/

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.

[ akpm@linux-foundation.org: build fixes on non-preempt architectures ]

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com>
Reviewed-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Paul E. McKenney 2008-01-25 21:08:24 +01:00 коммит произвёл Ingo Molnar
Родитель e0ecfa7917
Коммит e260be673a
13 изменённых файлов: 1395 добавлений и 8 удалений
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1
fs/Kconfig
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@ -2130,4 +2130,3 @@ source "fs/nls/Kconfig"
source "fs/dlm/Kconfig"
endmenu

3
include/linux/rcuclassic.h
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@ -157,5 +157,8 @@ 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 */

13
include/linux/rcupdate.h
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@ -53,7 +53,11 @@ 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
@ -231,13 +235,12 @@ extern void call_rcu_bh(struct rcu_head *head,
/* Exported common interfaces */
extern void synchronize_rcu(void);
extern void rcu_barrier(void);
/* Internal to kernel */
extern void rcu_init(void);
extern void rcu_check_callbacks(int cpu, int user);
extern long rcu_batches_completed(void);
extern long rcu_batches_completed_bh(void);
/* Internal to kernel */
extern void rcu_init(void);
extern int rcu_needs_cpu(int cpu);
#endif /* __KERNEL__ */
#endif /* __LINUX_RCUPDATE_H */

86
include/linux/rcupreempt.h Normal file
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@ -0,0 +1,86 @@
/*
* 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(); }
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);
extern long rcu_batches_completed(void);
/*
* Return the number of RCU batches processed thus far. Useful for debug
* and statistic. The _bh variant is identifcal to straight RCU
*/
static inline long rcu_batches_completed_bh(void)
{
return rcu_batches_completed();
}
#ifdef CONFIG_RCU_TRACE
struct rcupreempt_trace;
extern long *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 */

99
include/linux/rcupreempt_trace.h Normal file
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@ -0,0 +1,99 @@
/*
* 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 the Preemptible Read-Copy Update mechanism see -
* http://lwn.net/Articles/253651/
*/
#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 */

5
include/linux/sched.h
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@ -974,6 +974,11 @@ struct task_struct {
int nr_cpus_allowed;
unsigned int 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

28
init/Kconfig
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@ -763,3 +763,31 @@ source "block/Kconfig"
config PREEMPT_NOTIFIERS
bool
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

10
kernel/Kconfig.preempt
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@ -63,3 +63,13 @@ config PREEMPT_BKL
Say Y here if you are building a kernel for a desktop system.
Say N if you are unsure.
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.

7
kernel/Makefile
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@ -6,7 +6,7 @@ obj-y = sched.o fork.o exec_domain.o panic.o printk.o profile.o \
exit.o itimer.o time.o softirq.o resource.o \
sysctl.o capability.o ptrace.o timer.o user.o user_namespace.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 \
utsname.o notifier.o
@ -52,6 +52,11 @@ obj-$(CONFIG_DETECT_SOFTLOCKUP) += softlockup.o
obj-$(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_TASK_DELAY_ACCT) += delayacct.o

4
kernel/fork.c
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@ -1045,6 +1045,10 @@ static struct task_struct *copy_process(unsigned long clone_flags,
copy_flags(clone_flags, p);
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);

1
kernel/rcuclassic.c
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@ -45,7 +45,6 @@
#include <linux/moduleparam.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
/* #include <linux/rcupdate.h> @@@ */
#include <linux/cpu.h>
#include <linux/mutex.h>

816
kernel/rcupreempt.c Normal file
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@ -0,0 +1,816 @@
/*
* 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
*
* Design Document: http://lwn.net/Articles/253651/
*
* 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>
/*
* 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 ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
/*
* PREEMPT_RCU data structures.
*/
/*
* GP_STAGES specifies the number of times the state machine has
* to go through the all the rcu_try_flip_states (see below)
* in a single Grace Period.
*
* GP in GP_STAGES stands for Grace Period ;)
*/
#define GP_STAGES 2
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;
long rcu_flipctr[2];
#ifdef CONFIG_RCU_TRACE
struct rcupreempt_trace trace;
#endif /* #ifdef CONFIG_RCU_TRACE */
};
/*
* States for rcu_try_flip() and friends.
*/
enum rcu_try_flip_states {
/*
* Stay here if nothing is happening. Flip the counter if somthing
* starts happening. Denoted by "I"
*/
rcu_try_flip_idle_state,
/*
* Wait here for all CPUs to notice that the counter has flipped. This
* prevents the old set of counters from ever being incremented once
* we leave this state, which in turn is necessary because we cannot
* test any individual counter for zero -- we can only check the sum.
* Denoted by "A".
*/
rcu_try_flip_waitack_state,
/*
* Wait here for the sum of the old per-CPU counters to reach zero.
* Denoted by "Z".
*/
rcu_try_flip_waitzero_state,
/*
* Wait here for each of the other CPUs to execute a memory barrier.
* This is necessary to ensure that these other CPUs really have
* completed executing their RCU read-side critical sections, despite
* their CPUs wildly reordering memory. Denoted by "M".
*/
rcu_try_flip_waitmb_state,
};
struct rcu_ctrlblk {
spinlock_t fliplock; /* Protect state-machine transitions. */
long completed; /* Number of last completed batch. */
enum rcu_try_flip_states rcu_try_flip_state; /* The current state of
the rcu state machine */
};
static DEFINE_PER_CPU(struct rcu_data, rcu_data);
static struct rcu_ctrlblk rcu_ctrlblk = {
.fliplock = __SPIN_LOCK_UNLOCKED(rcu_ctrlblk.fliplock),
.completed = 0,
.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_SHARED_ALIGNED(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_SHARED_ALIGNED(enum rcu_mb_flag_values, rcu_mb_flag)
= rcu_mb_done;
/*
* 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);
EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
void __rcu_read_lock(void)
{
int idx;
struct task_struct *t = current;
int nesting;
nesting = ACCESS_ONCE(t->rcu_read_lock_nesting);
if (nesting != 0) {
/* An earlier rcu_read_lock() covers us, just count it. */
t->rcu_read_lock_nesting = nesting + 1;
} else {
unsigned long flags;
/*
* We disable interrupts for the following reasons:
* - If we get scheduling clock interrupt here, and we
* end up acking the counter flip, it's like a promise
* that we will never increment the old counter again.
* Thus we will break that promise if that
* scheduling clock interrupt happens between the time
* we pick the .completed field and the time that we
* increment our counter.
*
* - We don't want to be preempted out here.
*
* NMIs can still occur, of course, and might themselves
* contain rcu_read_lock().
*/
local_irq_save(flags);
/*
* 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 = ACCESS_ONCE(rcu_ctrlblk.completed) & 0x1;
ACCESS_ONCE(RCU_DATA_ME()->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.
*/
ACCESS_ONCE(t->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().
*/
ACCESS_ONCE(t->rcu_flipctr_idx) = idx;
local_irq_restore(flags);
}
}
EXPORT_SYMBOL_GPL(__rcu_read_lock);
void __rcu_read_unlock(void)
{
int idx;
struct task_struct *t = current;
int nesting;
nesting = ACCESS_ONCE(t->rcu_read_lock_nesting);
if (nesting > 1) {
/*
* We are still protected by the enclosing rcu_read_lock(),
* so simply decrement the counter.
*/
t->rcu_read_lock_nesting = nesting - 1;
} else {
unsigned long flags;
/*
* 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(flags);
/*
* 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.
*/
idx = ACCESS_ONCE(t->rcu_flipctr_idx);
/*
* 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.
*/
ACCESS_ONCE(t->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 counter on
* their own. They will also clobber ->rcu_flipctr_idx,
* but that is OK, since we have already fetched it.
*/
ACCESS_ONCE(RCU_DATA_ME()->rcu_flipctr[idx])--;
local_irq_restore(flags);
}
}
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 += RCU_DATA_CPU(cpu)->rcu_flipctr[lastidx];
if (sum != 0) {
RCU_TRACE_ME(rcupreempt_trace_try_flip_ze1);
return 0;
}
/*
* This ensures that the other CPUs see the call for
* memory barriers -after- the sum to zero has been
* detected here
*/
smp_mb(); /* ^^^^^^^^^^^^ */
/* 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 GP_STAGES 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 flags;
RCU_TRACE_ME(rcupreempt_trace_try_flip_1);
if (unlikely(!spin_trylock_irqsave(&rcu_ctrlblk.fliplock, flags))) {
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_ctrlblk.rcu_try_flip_state) {
case rcu_try_flip_idle_state:
if (rcu_try_flip_idle())
rcu_ctrlblk.rcu_try_flip_state =
rcu_try_flip_waitack_state;
break;
case rcu_try_flip_waitack_state:
if (rcu_try_flip_waitack())
rcu_ctrlblk.rcu_try_flip_state =
rcu_try_flip_waitzero_state;
break;
case rcu_try_flip_waitzero_state:
if (rcu_try_flip_waitzero())
rcu_ctrlblk.rcu_try_flip_state =
rcu_try_flip_waitmb_state;
break;
case rcu_try_flip_waitmb_state:
if (rcu_try_flip_waitmb())
rcu_ctrlblk.rcu_try_flip_state =
rcu_try_flip_idle_state;
}
spin_unlock_irqrestore(&rcu_ctrlblk.fliplock, flags);
}
/*
* 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 flags;
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, flags);
RCU_TRACE_RDP(rcupreempt_trace_check_callbacks, rdp);
__rcu_advance_callbacks(rdp);
if (rdp->donelist == NULL) {
spin_unlock_irqrestore(&rdp->lock, flags);
} else {
spin_unlock_irqrestore(&rdp->lock, flags);
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 flags;
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, flags);
RCU_TRACE_RDP(rcupreempt_trace_check_callbacks, rdp);
__rcu_advance_callbacks(rdp);
spin_unlock_irqrestore(&rdp->lock, flags);
}
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 call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
{
unsigned long flags;
struct rcu_data *rdp;
head->func = func;
head->next = NULL;
local_irq_save(flags);
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(flags);
}
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 "Preemptible 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;
rdp->rcu_flipctr[0] = 0;
rdp->rcu_flipctr[1] = 0;
}
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
long *rcupreempt_flipctr(int cpu)
{
return &RCU_DATA_CPU(cpu)->rcu_flipctr[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_ctrlblk.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 */

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kernel/rcupreempt_trace.c Normal file
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/*
* 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) {
long *flipctr = rcupreempt_flipctr(cpu);
cnt += snprintf(&rcupreempt_trace_buf[cnt],
RCUPREEMPT_TRACE_BUF_SIZE - cnt,
"%3d %4ld %3ld %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);