/* * Read-Copy Update mechanism for mutual exclusion (RT implementation) * * 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, 2006 * * Author: Paul McKenney <paulmck@us.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 - * Documentation/RCU * */ #ifndef __LINUX_RCUPREEMPT_H #define __LINUX_RCUPREEMPT_H #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_dyntick_sched { int dynticks; int dynticks_snap; int sched_qs; int sched_qs_snap; int sched_dynticks_snap; }; DECLARE_PER_CPU(struct rcu_dyntick_sched, rcu_dyntick_sched); static inline void rcu_qsctr_inc(int cpu) { struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu); rdssp->sched_qs++; } #define rcu_bh_qsctr_inc(cpu) /* * Someone might want to pass call_rcu_bh as a function pointer. * So this needs to just be a rename and not a macro function. * (no parentheses) */ #define call_rcu_bh call_rcu /** * call_rcu_sched - Queue RCU callback for invocation after sched grace period. * @head: structure to be used for queueing the RCU updates. * @func: actual update function to be invoked after the grace period * * The update function will be invoked some time after a full * synchronize_sched()-style grace period elapses, in other words after * all currently executing preempt-disabled sections of code (including * hardirq handlers, NMI handlers, and local_irq_save() blocks) have * completed. */ extern void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *head)); extern void __rcu_read_lock(void) __acquires(RCU); extern void __rcu_read_unlock(void) __releases(RCU); extern int rcu_pending(int cpu); extern int rcu_needs_cpu(int cpu); #define __rcu_read_lock_bh() { rcu_read_lock(); local_bh_disable(); } #define __rcu_read_unlock_bh() { local_bh_enable(); rcu_read_unlock(); } extern void __synchronize_sched(void); extern void __rcu_init(void); extern void rcu_init_sched(void); extern void rcu_check_callbacks(int cpu, int user); extern void rcu_restart_cpu(int cpu); extern long rcu_batches_completed(void); /* * Return the number of RCU batches processed thus far. Useful for debug * and statistic. The _bh variant is identifcal to straight RCU */ static inline long rcu_batches_completed_bh(void) { return rcu_batches_completed(); } #ifdef CONFIG_RCU_TRACE struct rcupreempt_trace; extern long *rcupreempt_flipctr(int cpu); extern long rcupreempt_data_completed(void); extern int rcupreempt_flip_flag(int cpu); extern int rcupreempt_mb_flag(int cpu); extern char *rcupreempt_try_flip_state_name(void); extern struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu); #endif struct softirq_action; #ifdef CONFIG_NO_HZ static inline void rcu_enter_nohz(void) { static DEFINE_RATELIMIT_STATE(rs, 10 * HZ, 1); smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ __get_cpu_var(rcu_dyntick_sched).dynticks++; WARN_ON_RATELIMIT(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1, &rs); } static inline void rcu_exit_nohz(void) { static DEFINE_RATELIMIT_STATE(rs, 10 * HZ, 1); __get_cpu_var(rcu_dyntick_sched).dynticks++; smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ WARN_ON_RATELIMIT(!(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1), &rs); } #else /* CONFIG_NO_HZ */ #define rcu_enter_nohz() do { } while (0) #define rcu_exit_nohz() do { } while (0) #endif /* CONFIG_NO_HZ */ /* * A context switch is a grace period for rcupreempt synchronize_rcu() * only during early boot, before the scheduler has been initialized. * So, how the heck do we get a context switch? Well, if the caller * invokes synchronize_rcu(), they are willing to accept a context * switch, so we simply pretend that one happened. * * After boot, there might be a blocked or preempted task in an RCU * read-side critical section, so we cannot then take the fastpath. */ static inline int rcu_blocking_is_gp(void) { return num_online_cpus() == 1 && !rcu_scheduler_active; } #endif /* __LINUX_RCUPREEMPT_H */