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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-06-21 17:10:40 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-08-31 14:44:02 -0700
commiteb75767be0e514f97bf1b5cec763696cfc7f7e2a (patch)
tree08cae2878e46409d6f5cffd0d37499bfa4851abc /kernel/rcutree_plugin.h
parent0edd1b1784cbdad55aca2c1293be018f53c0ab1d (diff)
nohz_full: Force RCU's grace-period kthreads onto timekeeping CPU
Because RCU's quiescent-state-forcing mechanism is used to drive the full-system-idle state machine, and because this mechanism is executed by RCU's grace-period kthreads, this commit forces these kthreads to run on the timekeeping CPU (tick_do_timer_cpu). To do otherwise would mean that the RCU grace-period kthreads would force the system into non-idle state every time they drove the state machine, which would be just a bit on the futile side. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel/rcutree_plugin.h')
-rw-r--r--kernel/rcutree_plugin.h21
1 files changed, 20 insertions, 1 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 45ebba747af4..130c97b027f2 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -2531,7 +2531,8 @@ static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
if (!*isidle || rdp->rsp != rcu_sysidle_state ||
cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu)
return;
- /* WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu); */
+ if (rcu_gp_in_progress(rdp->rsp))
+ WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu);
/* Pick up current idle and NMI-nesting counter and check. */
cur = atomic_read(&rdtp->dynticks_idle);
@@ -2557,6 +2558,20 @@ static bool is_sysidle_rcu_state(struct rcu_state *rsp)
}
/*
+ * Bind the grace-period kthread for the sysidle flavor of RCU to the
+ * timekeeping CPU.
+ */
+static void rcu_bind_gp_kthread(void)
+{
+ int cpu = ACCESS_ONCE(tick_do_timer_cpu);
+
+ if (cpu < 0 || cpu >= nr_cpu_ids)
+ return;
+ if (raw_smp_processor_id() != cpu)
+ set_cpus_allowed_ptr(current, cpumask_of(cpu));
+}
+
+/*
* Return a delay in jiffies based on the number of CPUs, rcu_node
* leaf fanout, and jiffies tick rate. The idea is to allow larger
* systems more time to transition to full-idle state in order to
@@ -2766,6 +2781,10 @@ static bool is_sysidle_rcu_state(struct rcu_state *rsp)
return false;
}
+static void rcu_bind_gp_kthread(void)
+{
+}
+
static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle,
unsigned long maxj)
{