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 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include/linux/hardirq.h') diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index 2961ec788046..49829988bfa0 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) /* -- cgit v1.2.3