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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
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3
kernel/time/tick-sched.c
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@@ -282,6 +282,7 @@ void tick_nohz_stop_sched_tick(void)
ts->idle_tick = ts->sched_timer.expires;
ts->tick_stopped = 1;
ts->idle_jiffies = last_jiffies;
rcu_enter_nohz();
}
/*
@@ -375,6 +376,8 @@ void tick_nohz_restart_sched_tick(void)
return;
}
rcu_exit_nohz();
/* Update jiffies first */
select_nohz_load_balancer(0);
now = ktime_get();