From e66c33d579ea566d10e8c8695a7168aae3e02992 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Fri, 12 Jul 2013 16:50:28 -0400 Subject: rcu: Add const annotation to char * for RCU tracepoints and functions All the RCU tracepoints and functions that reference char pointers do so with just 'char *' even though they do not modify the contents of the string itself. This will cause warnings if a const char * is used in one of these functions. The RCU tracepoints store the pointer to the string to refer back to them when the trace output is displayed. As this can be minutes, hours or even days later, those strings had better be constant. This change also opens the door to allow the RCU tracepoint strings and their addresses to be exported so that userspace tracing tools can translate the contents of the pointers of the RCU tracepoints. Signed-off-by: Steven Rostedt --- include/linux/rcupdate.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 4b14bdc911d7..0c38abbe6e35 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -52,7 +52,7 @@ extern int rcutorture_runnable; /* for sysctl */ #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) extern void rcutorture_record_test_transition(void); extern void rcutorture_record_progress(unsigned long vernum); -extern void do_trace_rcu_torture_read(char *rcutorturename, +extern void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, unsigned long secs, unsigned long c_old, @@ -65,7 +65,7 @@ static inline void rcutorture_record_progress(unsigned long vernum) { } #ifdef CONFIG_RCU_TRACE -extern void do_trace_rcu_torture_read(char *rcutorturename, +extern void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, unsigned long secs, unsigned long c_old, -- cgit v1.2.3 From feed66ed26a53e700ca02ce1744fed7d0c647292 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 9 May 2013 08:55:54 -0700 Subject: rcu: Eliminate unused APIs intended for adaptive ticks The rcu_user_enter_after_irq() and rcu_user_exit_after_irq() functions were intended for use by adaptive ticks, but changes in implementation have rendered them unnecessary. This commit therefore removes them. Reported-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- include/linux/rcupdate.h | 4 ---- 1 file changed, 4 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 0c38abbe6e35..30bea9c25735 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -229,13 +229,9 @@ extern void rcu_irq_exit(void); #ifdef CONFIG_RCU_USER_QS extern void rcu_user_enter(void); extern void rcu_user_exit(void); -extern void rcu_user_enter_after_irq(void); -extern void rcu_user_exit_after_irq(void); #else static inline void rcu_user_enter(void) { } static inline void rcu_user_exit(void) { } -static inline void rcu_user_enter_after_irq(void) { } -static inline void rcu_user_exit_after_irq(void) { } static inline void rcu_user_hooks_switch(struct task_struct *prev, struct task_struct *next) { } #endif /* CONFIG_RCU_USER_QS */ -- cgit v1.2.3 From 0edd1b1784cbdad55aca2c1293be018f53c0ab1d Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 21 Jun 2013 16:37:22 -0700 Subject: nohz_full: Add full-system-idle state machine This commit adds the state machine that takes the per-CPU idle data as input and produces a full-system-idle indication as output. This state machine is driven out of RCU's quiescent-state-forcing mechanism, which invokes rcu_sysidle_check_cpu() to collect per-CPU idle state and then rcu_sysidle_report() to drive the state machine. The full-system-idle state is sampled using rcu_sys_is_idle(), which also drives the state machine if RCU is idle (and does so by forcing RCU to become non-idle). This function returns true if all but the timekeeping CPU (tick_do_timer_cpu) are idle and have been idle long enough to avoid memory contention on the full_sysidle_state state variable. The rcu_sysidle_force_exit() may be called externally to reset the state machine back into non-idle state. For large systems the state machine is driven out of RCU's force-quiescent-state logic, which provides good scalability at the price of millisecond-scale latencies on the transition to full-system-idle state. This is not so good for battery-powered systems, which are usually small enough that they don't need to care about scalability, but which do care deeply about energy efficiency. Small systems therefore drive the state machine directly out of the idle-entry code. The number of CPUs in a "small" system is defined by a new NO_HZ_FULL_SYSIDLE_SMALL Kconfig parameter, which defaults to 8. Note that this is a build-time definition. Signed-off-by: Paul E. McKenney Cc: Frederic Weisbecker Cc: Steven Rostedt Cc: Lai Jiangshan [ paulmck: Use true and false for boolean constants per Lai Jiangshan. ] Reviewed-by: Josh Triplett [ paulmck: Simplify logic and provide better comments for memory barriers, based on review comments and questions by Lai Jiangshan. ] --- include/linux/rcupdate.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 30bea9c25735..f1f1bc39346b 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -1011,4 +1011,22 @@ static inline bool rcu_is_nocb_cpu(int cpu) { return false; } #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ +/* Only for use by adaptive-ticks code. */ +#ifdef CONFIG_NO_HZ_FULL_SYSIDLE +extern bool rcu_sys_is_idle(void); +extern void rcu_sysidle_force_exit(void); +#else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ + +static inline bool rcu_sys_is_idle(void) +{ + return false; +} + +static inline void rcu_sysidle_force_exit(void) +{ +} + +#endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ + + #endif /* __LINUX_RCUPDATE_H */ -- cgit v1.2.3