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rcu: add support for dynamic ticks and preempt rcu

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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 <srostedt@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Steven Rostedt
2008-02-29 18:46:50 +01:00
committed by Ingo Molnar
parent c0f4133b8f
commit 2232c2d8e0
6 changed files with 259 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/linux/hardirq.h
+10
View File
@@ -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)
/*
include/linux/rcuclassic.h
+3
View File
@@ -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 */
include/linux/rcupreempt.h
+22
View File
@@ -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 */