http://www.ousob.com --- Legacy Redefined OuSob - File: /wwwroot/clipx/usr/include/linux/rcupdate.h

/* * 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/spinlock.h> #include <linux/threads.h> #include <linux/percpu.h> #include <linux/cpumask.h> #include <linux/seqlock.h> /** * struct rcu_head - callback structure for use with RCU * @next: next update requests in a list * @func: actual update function to call after the grace period. */ struct rcu_head { struct rcu_head *next; void (*func)(struct rcu_head *head); }; #define RCU_HEAD_INIT { .next = NULL, .func = NULL } #define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT #define INIT_RCU_HEAD(ptr) do { \ (ptr)->next = NULL; (ptr)->func = NULL; \ } while (0) /* Global control variables for rcupdate callback mechanism. */ struct rcu_ctrlblk { long cur; /* Current batch number. */ long completed; /* Number of the last completed batch */ int next_pending; /* Is the next batch already waiting? */ spinlock_t lock ____cacheline_internodealigned_in_smp; cpumask_t cpumask; /* CPUs that need to switch in order */ /* for current batch to proceed. */ } ____cacheline_internodealigned_in_smp; /* 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 { /* 1) quiescent state handling : */ long quiescbatch; /* Batch # for grace period */ int passed_quiesc; /* User-mode/idle loop etc. */ int qs_pending; /* core waits for quiesc state */ /* 2) batch handling */ long batch; /* Batch # for current RCU batch */ struct rcu_head *nxtlist; struct rcu_head **nxttail; long qlen; /* # of queued callbacks */ struct rcu_head *curlist; struct rcu_head **curtail; struct rcu_head *donelist; struct rcu_head **donetail; long blimit; /* Upper limit on a processed batch */ int cpu; struct rcu_head barrier; #ifdef CONFIG_SMP long last_rs_qlen; /* qlen during the last resched */ #endif }; DECLARE_PER_CPU(struct rcu_data, rcu_data); DECLARE_PER_CPU(struct rcu_data, rcu_bh_data); extern struct rcu_ctrlblk rcu_ctrlblk; extern struct rcu_ctrlblk rcu_bh_ctrlblk; /* * Increment the quiescent state counter. * The counter is a bit degenerated: We do not need to know * how many quiescent states passed, just if there was at least * one since the start of the grace period. Thus just a flag. */ static inline void rcu_qsctr_inc(int cpu) { struct rcu_data *rdp = &per_cpu(rcu_data, cpu); rdp->passed_quiesc = 1; } static inline void rcu_bh_qsctr_inc(int cpu) { struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); rdp->passed_quiesc = 1; } extern int rcu_pending(int cpu); /** * rcu_read_lock - mark the beginning of an RCU read-side critical section. * * When synchronize_rcu() is invoked on one CPU while other CPUs * are within RCU read-side critical sections, then the * synchronize_rcu() is guaranteed to block until after all the other * CPUs exit their critical sections. Similarly, if call_rcu() is invoked * on one CPU while other CPUs are within RCU read-side critical * sections, invocation of the corresponding RCU callback is deferred * until after the all the other CPUs exit their critical sections. * * Note, however, that RCU callbacks are permitted to run concurrently * with RCU read-side critical sections. One way that this can happen * is via the following sequence of events: (1) CPU 0 enters an RCU * read-side critical section, (2) CPU 1 invokes call_rcu() to register * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU * callback is invoked. This is legal, because the RCU read-side critical * section that was running concurrently with the call_rcu() (and which * therefore might be referencing something that the corresponding RCU * callback would free up) has completed before the corresponding * RCU callback is invoked. * * RCU read-side critical sections may be nested. Any deferred actions * will be deferred until the outermost RCU read-side critical section * completes. * * It is illegal to block while in an RCU read-side critical section. */ #define rcu_read_lock() preempt_disable() /** * rcu_read_unlock - marks the end of an RCU read-side critical section. * * See rcu_read_lock() for more information. */ #define rcu_read_unlock() preempt_enable() /* * So where is rcu_write_lock()? It does not exist, as there is no * way for writers to lock out RCU readers. This is a feature, not * a bug -- this property is what provides RCU's performance benefits. * Of course, writers must coordinate with each other. The normal * spinlock primitives work well for this, but any other technique may be * used as well. RCU does not care how the writers keep out of each * others' way, as long as they do so. */ /** * rcu_read_lock_bh - mark the beginning of a softirq-only RCU critical section * * This is equivalent of rcu_read_lock(), but to be used when updates * are being done using call_rcu_bh(). Since call_rcu_bh() callbacks * consider completion of a softirq handler to be a quiescent state, * a process in RCU read-side critical section must be protected by * disabling softirqs. Read-side critical sections in interrupt context * can use just rcu_read_lock(). * */ #define rcu_read_lock_bh() local_bh_disable() /* * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section * * See rcu_read_lock_bh() for more information. */ #define rcu_read_unlock_bh() local_bh_enable() /** * rcu_dereference - fetch an RCU-protected pointer in an * RCU read-side critical section. This pointer may later * be safely dereferenced. * * Inserts memory barriers on architectures that require them * (currently only the Alpha), and, more importantly, documents * exactly which pointers are protected by RCU. */ #define rcu_dereference(p) ({ \ typeof(p) _________p1 = p; \ smp_read_barrier_depends(); \ (_________p1); \ }) /** * rcu_assign_pointer - assign (publicize) a pointer to a newly * initialized structure that will be dereferenced by RCU read-side * critical sections. Returns the value assigned. * * Inserts memory barriers on architectures that require them * (pretty much all of them other than x86), and also prevents * the compiler from reordering the code that initializes the * structure after the pointer assignment. More importantly, this * call documents which pointers will be dereferenced by RCU read-side * code. */ #define rcu_assign_pointer(p, v) ({ \ smp_wmb(); \ (p) = (v); \ }) /** * synchronize_sched - block until all CPUs have exited any non-preemptive * kernel code sequences. * * This means that all preempt_disable code sequences, including NMI and * hardware-interrupt handlers, in progress on entry will have completed * before this primitive returns. However, this does not guarantee that * softirq handlers will have completed, since in some kernels, these * handlers can run in process context, and can block. * * This primitive provides the guarantees made by the (deprecated) * synchronize_kernel() API. In contrast, synchronize_rcu() only * guarantees that rcu_read_lock() sections will have completed. * In "classic RCU", these two guarantees happen to be one and * the same, but can differ in realtime RCU implementations. */ #define synchronize_sched() synchronize_rcu() 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); /* Exported interfaces */ extern void FASTCALL(call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *head))); extern void FASTCALL(call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *head))); extern __deprecated_for_modules void synchronize_kernel(void); extern void synchronize_rcu(void); void synchronize_idle(void); extern void rcu_barrier(void); #endif /* __KERNEL__ */ #endif /* __LINUX_RCUPDATE_H */