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| 422 | giacomo | 1 | /* |
| 2 | * Read-Copy Update mechanism for mutual exclusion |
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| 3 | * |
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| 4 | * This program is free software; you can redistribute it and/or modify |
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| 5 | * it under the terms of the GNU General Public License as published by |
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| 6 | * the Free Software Foundation; either version 2 of the License, or |
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| 7 | * (at your option) any later version. |
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| 8 | * |
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| 9 | * This program is distributed in the hope that it will be useful, |
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| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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| 12 | * GNU General Public License for more details. |
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| 13 | * |
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| 14 | * You should have received a copy of the GNU General Public License |
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| 15 | * along with this program; if not, write to the Free Software |
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| 16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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| 17 | * |
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| 18 | * Copyright (C) IBM Corporation, 2001 |
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| 19 | * |
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| 20 | * Author: Dipankar Sarma <dipankar@in.ibm.com> |
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| 21 | * |
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| 22 | * Based on the original work by Paul McKenney <paul.mckenney@us.ibm.com> |
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| 23 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
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| 24 | * Papers: |
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| 25 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf |
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| 26 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) |
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| 27 | * |
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| 28 | * For detailed explanation of Read-Copy Update mechanism see - |
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| 29 | * http://lse.sourceforge.net/locking/rcupdate.html |
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| 30 | * |
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| 31 | */ |
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| 32 | |||
| 33 | #ifndef __LINUX_RCUPDATE_H |
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| 34 | #define __LINUX_RCUPDATE_H |
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| 35 | |||
| 36 | #ifdef __KERNEL__ |
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| 37 | |||
| 38 | #include <linux/cache.h> |
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| 39 | #include <linux/list.h> |
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| 40 | #include <linux/spinlock.h> |
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| 41 | #include <linux/threads.h> |
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| 42 | #include <linux/percpu.h> |
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| 43 | #include <linux/cpumask.h> |
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| 44 | |||
| 45 | /** |
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| 46 | * struct rcu_head - callback structure for use with RCU |
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| 47 | * @list: list_head to queue the update requests |
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| 48 | * @func: actual update function to call after the grace period. |
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| 49 | * @arg: argument to be passed to the actual update function. |
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| 50 | */ |
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| 51 | struct rcu_head { |
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| 52 | struct list_head list; |
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| 53 | void (*func)(void *obj); |
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| 54 | void *arg; |
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| 55 | }; |
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| 56 | |||
| 57 | #define RCU_HEAD_INIT(head) \ |
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| 58 | { list: LIST_HEAD_INIT(head.list), func: NULL, arg: NULL } |
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| 59 | #define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT(head) |
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| 60 | #define INIT_RCU_HEAD(ptr) do { \ |
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| 61 | INIT_LIST_HEAD(&(ptr)->list); (ptr)->func = NULL; (ptr)->arg = NULL; \ |
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| 62 | } while (0) |
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| 63 | |||
| 64 | |||
| 65 | |||
| 66 | /* Control variables for rcupdate callback mechanism. */ |
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| 67 | struct rcu_ctrlblk { |
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| 68 | spinlock_t mutex; /* Guard this struct */ |
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| 69 | long curbatch; /* Current batch number. */ |
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| 70 | long maxbatch; /* Max requested batch number. */ |
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| 71 | cpumask_t rcu_cpu_mask; /* CPUs that need to switch in order */ |
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| 72 | /* for current batch to proceed. */ |
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| 73 | }; |
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| 74 | |||
| 75 | /* Is batch a before batch b ? */ |
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| 76 | static inline int rcu_batch_before(long a, long b) |
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| 77 | { |
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| 78 | return (a - b) < 0; |
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| 79 | } |
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| 80 | |||
| 81 | /* Is batch a after batch b ? */ |
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| 82 | static inline int rcu_batch_after(long a, long b) |
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| 83 | { |
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| 84 | return (a - b) > 0; |
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| 85 | } |
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| 86 | |||
| 87 | /* |
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| 88 | * Per-CPU data for Read-Copy UPdate. |
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| 89 | * nxtlist - new callbacks are added here |
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| 90 | * curlist - current batch for which quiescent cycle started if any |
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| 91 | */ |
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| 92 | struct rcu_data { |
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| 93 | long qsctr; /* User-mode/idle loop etc. */ |
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| 94 | long last_qsctr; /* value of qsctr at beginning */ |
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| 95 | /* of rcu grace period */ |
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| 96 | long batch; /* Batch # for current RCU batch */ |
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| 97 | struct list_head nxtlist; |
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| 98 | struct list_head curlist; |
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| 99 | }; |
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| 100 | |||
| 101 | DECLARE_PER_CPU(struct rcu_data, rcu_data); |
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| 102 | extern struct rcu_ctrlblk rcu_ctrlblk; |
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| 103 | |||
| 104 | #define RCU_qsctr(cpu) (per_cpu(rcu_data, (cpu)).qsctr) |
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| 105 | #define RCU_last_qsctr(cpu) (per_cpu(rcu_data, (cpu)).last_qsctr) |
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| 106 | #define RCU_batch(cpu) (per_cpu(rcu_data, (cpu)).batch) |
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| 107 | #define RCU_nxtlist(cpu) (per_cpu(rcu_data, (cpu)).nxtlist) |
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| 108 | #define RCU_curlist(cpu) (per_cpu(rcu_data, (cpu)).curlist) |
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| 109 | |||
| 110 | #define RCU_QSCTR_INVALID 0 |
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| 111 | |||
| 112 | static inline int rcu_pending(int cpu) |
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| 113 | { |
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| 114 | if ((!list_empty(&RCU_curlist(cpu)) && |
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| 115 | rcu_batch_before(RCU_batch(cpu), rcu_ctrlblk.curbatch)) || |
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| 116 | (list_empty(&RCU_curlist(cpu)) && |
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| 117 | !list_empty(&RCU_nxtlist(cpu))) || |
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| 118 | cpu_isset(cpu, rcu_ctrlblk.rcu_cpu_mask)) |
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| 119 | return 1; |
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| 120 | else |
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| 121 | return 0; |
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| 122 | } |
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| 123 | |||
| 124 | #define rcu_read_lock() preempt_disable() |
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| 125 | #define rcu_read_unlock() preempt_enable() |
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| 126 | |||
| 127 | extern void rcu_init(void); |
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| 128 | extern void rcu_check_callbacks(int cpu, int user); |
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| 129 | |||
| 130 | /* Exported interfaces */ |
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| 131 | extern void FASTCALL(call_rcu(struct rcu_head *head, |
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| 132 | void (*func)(void *arg), void *arg)); |
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| 133 | extern void synchronize_kernel(void); |
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| 134 | |||
| 135 | #endif /* __KERNEL__ */ |
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| 136 | #endif /* __LINUX_RCUPDATE_H */ |