include/linux/rcupreempt.h

   1 /*
   2  * Read-Copy Update mechanism for mutual exclusion (RT implementation)
   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  *
  18  * Copyright (C) IBM Corporation, 2006
  19  *
  20  * Author:  Paul McKenney <paulmck@us.ibm.com>
  21  *
  22  * Based on the original work by Paul McKenney <paul.mckenney@us.ibm.com>
  23  * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
  24  * Papers:
  25  * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
  26  * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
  27  *
  28  * For detailed explanation of Read-Copy Update mechanism see -
  29  *              Documentation/RCU
  30  *
  31  */
  32
  33 #ifndef __LINUX_RCUPREEMPT_H
  34 #define __LINUX_RCUPREEMPT_H
  35
  36 #include <linux/cache.h>
  37 #include <linux/spinlock.h>
  38 #include <linux/threads.h>
  39 #include <linux/smp.h>
  40 #include <linux/cpumask.h>
  41 #include <linux/seqlock.h>
  42
  43 extern void rcu_qsctr_inc(int cpu);
  44 static inline void rcu_bh_qsctr_inc(int cpu) { }
  45
  46 /*
  47  * Someone might want to pass call_rcu_bh as a function pointer.
  48  * So this needs to just be a rename and not a macro function.
  49  *  (no parentheses)
  50  */
  51 #define call_rcu_bh             call_rcu
  52
  53 /**
  54  * call_rcu_sched - Queue RCU callback for invocation after sched grace period.
  55  * @head: structure to be used for queueing the RCU updates.
  56  * @func: actual update function to be invoked after the grace period
  57  *
  58  * The update function will be invoked some time after a full
  59  * synchronize_sched()-style grace period elapses, in other words after
  60  * all currently executing preempt-disabled sections of code (including
  61  * hardirq handlers, NMI handlers, and local_irq_save() blocks) have
  62  * completed.
  63  */
  64 extern void call_rcu_sched(struct rcu_head *head,
  65                            void (*func)(struct rcu_head *head));
  66
  67 extern void __rcu_read_lock(void)       __acquires(RCU);
  68 extern void __rcu_read_unlock(void)     __releases(RCU);
  69 extern int rcu_pending(int cpu);
  70 extern int rcu_needs_cpu(int cpu);
  71
  72 #define __rcu_read_lock_bh()    { rcu_read_lock(); local_bh_disable(); }
  73 #define __rcu_read_unlock_bh()  { local_bh_enable(); rcu_read_unlock(); }
  74
  75 extern void __synchronize_sched(void);
  76
  77 extern void __rcu_init(void);
  78 extern void rcu_init_sched(void);
  79 extern void rcu_check_callbacks(int cpu, int user);
  80 extern void rcu_restart_cpu(int cpu);
  81 extern long rcu_batches_completed(void);
  82
  83 /*
  84  * Return the number of RCU batches processed thus far. Useful for debug
  85  * and statistic. The _bh variant is identifcal to straight RCU
  86  */
  87 static inline long rcu_batches_completed_bh(void)
  88 {
  89         return rcu_batches_completed();
  90 }
  91
  92 #ifdef CONFIG_RCU_TRACE
  93 struct rcupreempt_trace;
  94 extern long *rcupreempt_flipctr(int cpu);
  95 extern long rcupreempt_data_completed(void);
  96 extern int rcupreempt_flip_flag(int cpu);
  97 extern int rcupreempt_mb_flag(int cpu);
  98 extern char *rcupreempt_try_flip_state_name(void);
  99 extern struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu);
 100 #endif
 101
 102 struct softirq_action;
 103
 104 #ifdef CONFIG_NO_HZ
 105 extern void rcu_enter_nohz(void);
 106 extern void rcu_exit_nohz(void);
 107 #else
 108 # define rcu_enter_nohz()       do { } while (0)
 109 # define rcu_exit_nohz()        do { } while (0)
 110 #endif
 111
 112 /*
 113  * A context switch is a grace period for rcupreempt synchronize_rcu()
 114  * only during early boot, before the scheduler has been initialized.
 115  * So, how the heck do we get a context switch?  Well, if the caller
 116  * invokes synchronize_rcu(), they are willing to accept a context
 117  * switch, so we simply pretend that one happened.
 118  *
 119  * After boot, there might be a blocked or preempted task in an RCU
 120  * read-side critical section, so we cannot then take the fastpath.
 121  */
 122 static inline int rcu_blocking_is_gp(void)
 123 {
 124         return num_online_cpus() == 1 && !rcu_scheduler_active;
 125 }
 126
 127 #endif /* __LINUX_RCUPREEMPT_H */