Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Read-Copy Update mechanism for mutual exclusion |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or modify |
| 5 | * it under the terms of the GNU General Public License as published by |
| 6 | * the Free Software Foundation; either version 2 of the License, or |
| 7 | * (at your option) any later version. |
| 8 | * |
| 9 | * This program is distributed in the hope that it will be useful, |
| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 12 | * GNU General Public License for more details. |
| 13 | * |
| 14 | * You should have received a copy of the GNU General Public License |
| 15 | * along with this program; if not, write to the Free Software |
| 16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 17 | * |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 18 | * Copyright IBM Corporation, 2001 |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 19 | * |
| 20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> |
| 21 | * Manfred Spraul <manfred@colorfullife.com> |
| 22 | * |
| 23 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
| 24 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
| 25 | * Papers: |
| 26 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf |
| 27 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) |
| 28 | * |
| 29 | * For detailed explanation of Read-Copy Update mechanism see - |
| 30 | * http://lse.sourceforge.net/locking/rcupdate.html |
| 31 | * |
| 32 | */ |
| 33 | #include <linux/types.h> |
| 34 | #include <linux/kernel.h> |
| 35 | #include <linux/init.h> |
| 36 | #include <linux/spinlock.h> |
| 37 | #include <linux/smp.h> |
| 38 | #include <linux/interrupt.h> |
| 39 | #include <linux/sched.h> |
| 40 | #include <asm/atomic.h> |
| 41 | #include <linux/bitops.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 42 | #include <linux/completion.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 43 | #include <linux/percpu.h> |
| 44 | #include <linux/notifier.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 45 | #include <linux/cpu.h> |
Ingo Molnar | 9331b31 | 2006-03-23 03:00:19 -0800 | [diff] [blame] | 46 | #include <linux/mutex.h> |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 47 | #include <linux/module.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 48 | |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 49 | struct rcu_synchronize { |
| 50 | struct rcu_head head; |
| 51 | struct completion completion; |
Oleg Nesterov | 69a0b31 | 2006-01-10 16:48:02 +0300 | [diff] [blame] | 52 | }; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 53 | |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 54 | static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL}; |
Dipankar Sarma | 21a1ea9 | 2006-03-07 21:55:33 -0800 | [diff] [blame] | 55 | static atomic_t rcu_barrier_cpu_count; |
Ingo Molnar | 9331b31 | 2006-03-23 03:00:19 -0800 | [diff] [blame] | 56 | static DEFINE_MUTEX(rcu_barrier_mutex); |
Dipankar Sarma | 21a1ea9 | 2006-03-07 21:55:33 -0800 | [diff] [blame] | 57 | static struct completion rcu_barrier_completion; |
| 58 | |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 59 | /* Because of FASTCALL declaration of complete, we use this wrapper */ |
| 60 | static void wakeme_after_rcu(struct rcu_head *head) |
Dipankar Sarma | 21a1ea9 | 2006-03-07 21:55:33 -0800 | [diff] [blame] | 61 | { |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 62 | struct rcu_synchronize *rcu; |
| 63 | |
| 64 | rcu = container_of(head, struct rcu_synchronize, head); |
| 65 | complete(&rcu->completion); |
Dipankar Sarma | 21a1ea9 | 2006-03-07 21:55:33 -0800 | [diff] [blame] | 66 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 67 | |
| 68 | /** |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 69 | * synchronize_rcu - wait until a grace period has elapsed. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 70 | * |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 71 | * Control will return to the caller some time after a full grace |
| 72 | * period has elapsed, in other words after all currently executing RCU |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 73 | * read-side critical sections have completed. RCU read-side critical |
| 74 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), |
| 75 | * and may be nested. |
| 76 | */ |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 77 | void synchronize_rcu(void) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 78 | { |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 79 | struct rcu_synchronize rcu; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 80 | |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 81 | init_completion(&rcu.completion); |
| 82 | /* Will wake me after RCU finished */ |
| 83 | call_rcu(&rcu.head, wakeme_after_rcu); |
| 84 | |
| 85 | /* Wait for it */ |
| 86 | wait_for_completion(&rcu.completion); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 87 | } |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 88 | EXPORT_SYMBOL_GPL(synchronize_rcu); |
Paul E. McKenney | c32e066 | 2006-06-27 02:54:04 -0700 | [diff] [blame] | 89 | |
Dipankar Sarma | ab4720e | 2005-12-12 00:37:05 -0800 | [diff] [blame] | 90 | static void rcu_barrier_callback(struct rcu_head *notused) |
| 91 | { |
| 92 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) |
| 93 | complete(&rcu_barrier_completion); |
| 94 | } |
| 95 | |
| 96 | /* |
| 97 | * Called with preemption disabled, and from cross-cpu IRQ context. |
| 98 | */ |
| 99 | static void rcu_barrier_func(void *notused) |
| 100 | { |
| 101 | int cpu = smp_processor_id(); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 102 | struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu); |
Dipankar Sarma | ab4720e | 2005-12-12 00:37:05 -0800 | [diff] [blame] | 103 | |
Dipankar Sarma | ab4720e | 2005-12-12 00:37:05 -0800 | [diff] [blame] | 104 | atomic_inc(&rcu_barrier_cpu_count); |
| 105 | call_rcu(head, rcu_barrier_callback); |
| 106 | } |
| 107 | |
| 108 | /** |
| 109 | * rcu_barrier - Wait until all the in-flight RCUs are complete. |
| 110 | */ |
| 111 | void rcu_barrier(void) |
| 112 | { |
| 113 | BUG_ON(in_interrupt()); |
Ingo Molnar | 9331b31 | 2006-03-23 03:00:19 -0800 | [diff] [blame] | 114 | /* Take cpucontrol mutex to protect against CPU hotplug */ |
| 115 | mutex_lock(&rcu_barrier_mutex); |
Dipankar Sarma | ab4720e | 2005-12-12 00:37:05 -0800 | [diff] [blame] | 116 | init_completion(&rcu_barrier_completion); |
| 117 | atomic_set(&rcu_barrier_cpu_count, 0); |
Paul E. McKenney | e0ecfa7 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 118 | /* |
| 119 | * The queueing of callbacks in all CPUs must be atomic with |
| 120 | * respect to RCU, otherwise one CPU may queue a callback, |
| 121 | * wait for a grace period, decrement barrier count and call |
| 122 | * complete(), while other CPUs have not yet queued anything. |
| 123 | * So, we need to make sure that grace periods cannot complete |
| 124 | * until all the callbacks are queued. |
| 125 | */ |
| 126 | rcu_read_lock(); |
Dipankar Sarma | ab4720e | 2005-12-12 00:37:05 -0800 | [diff] [blame] | 127 | on_each_cpu(rcu_barrier_func, NULL, 0, 1); |
Paul E. McKenney | e0ecfa7 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 128 | rcu_read_unlock(); |
Dipankar Sarma | ab4720e | 2005-12-12 00:37:05 -0800 | [diff] [blame] | 129 | wait_for_completion(&rcu_barrier_completion); |
Ingo Molnar | 9331b31 | 2006-03-23 03:00:19 -0800 | [diff] [blame] | 130 | mutex_unlock(&rcu_barrier_mutex); |
Dipankar Sarma | ab4720e | 2005-12-12 00:37:05 -0800 | [diff] [blame] | 131 | } |
| 132 | EXPORT_SYMBOL_GPL(rcu_barrier); |
| 133 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 134 | void __init rcu_init(void) |
| 135 | { |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 136 | __rcu_init(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 137 | } |
| 138 | |