From 2232c2d8e0a6a31061dec311f3d1cf7624bc14f1 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 29 Feb 2008 18:46:50 +0100 Subject: rcu: add support for dynamic ticks and preempt rcu The PREEMPT-RCU can get stuck if a CPU goes idle and NO_HZ is set. The idle CPU will not progress the RCU through its grace period and a synchronize_rcu my get stuck. Without this patch I have a box that will not boot when PREEMPT_RCU and NO_HZ are set. That same box boots fine with this patch. This patch comes from the -rt kernel where it has been tested for several months. Signed-off-by: Steven Rostedt Signed-off-by: Paul E. McKenney Signed-off-by: Ingo Molnar --- include/linux/hardirq.h | 10 ++++++++++ include/linux/rcuclassic.h | 3 +++ include/linux/rcupreempt.h | 22 ++++++++++++++++++++++ 3 files changed, 35 insertions(+) (limited to 'include') diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index 2961ec78804..49829988bfa 100644 --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -109,6 +109,14 @@ static inline void account_system_vtime(struct task_struct *tsk) } #endif +#if defined(CONFIG_PREEMPT_RCU) && defined(CONFIG_NO_HZ) +extern void rcu_irq_enter(void); +extern void rcu_irq_exit(void); +#else +# define rcu_irq_enter() do { } while (0) +# define rcu_irq_exit() do { } while (0) +#endif /* CONFIG_PREEMPT_RCU */ + /* * It is safe to do non-atomic ops on ->hardirq_context, * because NMI handlers may not preempt and the ops are @@ -117,6 +125,7 @@ static inline void account_system_vtime(struct task_struct *tsk) */ #define __irq_enter() \ do { \ + rcu_irq_enter(); \ account_system_vtime(current); \ add_preempt_count(HARDIRQ_OFFSET); \ trace_hardirq_enter(); \ @@ -135,6 +144,7 @@ extern void irq_enter(void); trace_hardirq_exit(); \ account_system_vtime(current); \ sub_preempt_count(HARDIRQ_OFFSET); \ + rcu_irq_exit(); \ } while (0) /* diff --git a/include/linux/rcuclassic.h b/include/linux/rcuclassic.h index 4d6624260b4..b3dccd68629 100644 --- a/include/linux/rcuclassic.h +++ b/include/linux/rcuclassic.h @@ -160,5 +160,8 @@ extern void rcu_restart_cpu(int cpu); extern long rcu_batches_completed(void); extern long rcu_batches_completed_bh(void); +#define rcu_enter_nohz() do { } while (0) +#define rcu_exit_nohz() do { } while (0) + #endif /* __KERNEL__ */ #endif /* __LINUX_RCUCLASSIC_H */ diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h index 60c2a033b19..01152ed532c 100644 --- a/include/linux/rcupreempt.h +++ b/include/linux/rcupreempt.h @@ -82,5 +82,27 @@ extern struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu); struct softirq_action; +#ifdef CONFIG_NO_HZ +DECLARE_PER_CPU(long, dynticks_progress_counter); + +static inline void rcu_enter_nohz(void) +{ + __get_cpu_var(dynticks_progress_counter)++; + WARN_ON(__get_cpu_var(dynticks_progress_counter) & 0x1); + mb(); +} + +static inline void rcu_exit_nohz(void) +{ + mb(); + __get_cpu_var(dynticks_progress_counter)++; + WARN_ON(!(__get_cpu_var(dynticks_progress_counter) & 0x1)); +} + +#else /* CONFIG_NO_HZ */ +#define rcu_enter_nohz() do { } while (0) +#define rcu_exit_nohz() do { } while (0) +#endif /* CONFIG_NO_HZ */ + #endif /* __KERNEL__ */ #endif /* __LINUX_RCUPREEMPT_H */ -- cgit v1.2.3-70-g09d2