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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 | /* * Read-Copy Update mechanism for mutual exclusion * * 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, 2001 * * Author: Dipankar Sarma <dipankar@in.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_RCUPDATE_H #define __LINUX_RCUPDATE_H #ifdef __KERNEL__ #include <linux/cache.h> #include <linux/list.h> #include <linux/spinlock.h> #include <linux/threads.h> #include <linux/percpu.h> /** * struct rcu_head - callback structure for use with RCU * @list: list_head to queue the update requests * @func: actual update function to call after the grace period. * @arg: argument to be passed to the actual update function. */ struct rcu_head { struct list_head list; void (*func)(void *obj); void *arg; }; #define RCU_HEAD_INIT(head) \ { list: LIST_HEAD_INIT(head.list), func: NULL, arg: NULL } #define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT(head) #define INIT_RCU_HEAD(ptr) do { \ INIT_LIST_HEAD(&(ptr)->list); (ptr)->func = NULL; (ptr)->arg = NULL; \ } while (0) /* Control variables for rcupdate callback mechanism. */ struct rcu_ctrlblk { spinlock_t mutex; /* Guard this struct */ long curbatch; /* Current batch number. */ long maxbatch; /* Max requested batch number. */ unsigned long rcu_cpu_mask; /* CPUs that need to switch in order */ /* for current batch to proceed. */ }; /* Is batch a before batch b ? */ static inline int rcu_batch_before(long a, long b) { return (a - b) < 0; } /* Is batch a after batch b ? */ static inline int rcu_batch_after(long a, long b) { return (a - b) > 0; } /* * Per-CPU data for Read-Copy UPdate. * nxtlist - new callbacks are added here * curlist - current batch for which quiescent cycle started if any */ struct rcu_data { long qsctr; /* User-mode/idle loop etc. */ long last_qsctr; /* value of qsctr at beginning */ /* of rcu grace period */ long batch; /* Batch # for current RCU batch */ struct list_head nxtlist; struct list_head curlist; }; DECLARE_PER_CPU(struct rcu_data, rcu_data); extern struct rcu_ctrlblk rcu_ctrlblk; #define RCU_qsctr(cpu) (per_cpu(rcu_data, (cpu)).qsctr) #define RCU_last_qsctr(cpu) (per_cpu(rcu_data, (cpu)).last_qsctr) #define RCU_batch(cpu) (per_cpu(rcu_data, (cpu)).batch) #define RCU_nxtlist(cpu) (per_cpu(rcu_data, (cpu)).nxtlist) #define RCU_curlist(cpu) (per_cpu(rcu_data, (cpu)).curlist) #define RCU_QSCTR_INVALID 0 static inline int rcu_pending(int cpu) { if ((!list_empty(&RCU_curlist(cpu)) && rcu_batch_before(RCU_batch(cpu), rcu_ctrlblk.curbatch)) || (list_empty(&RCU_curlist(cpu)) && !list_empty(&RCU_nxtlist(cpu))) || test_bit(cpu, &rcu_ctrlblk.rcu_cpu_mask)) return 1; else return 0; } #define rcu_read_lock() preempt_disable() #define rcu_read_unlock() preempt_enable() extern void rcu_init(void); extern void rcu_check_callbacks(int cpu, int user); /* Exported interfaces */ extern void FASTCALL(call_rcu(struct rcu_head *head, void (*func)(void *arg), void *arg)); extern void synchronize_kernel(void); #endif /* __KERNEL__ */ #endif /* __LINUX_RCUPDATE_H */ |