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rcu: Improve comments for hotplug/suspend/hibernate functions 

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2017-03-23 13:21:30 -07:00
parent 48ac34666f
commit deb34f3643
1 changed files with 37 additions and 4 deletions
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41
kernel/rcu/tree.c
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@ -3894,6 +3894,10 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
/*
* Invoked early in the CPU-online process, when pretty much all
* services are available. The incoming CPU is not present.
*/
int rcutree_prepare_cpu(unsigned int cpu)
{
struct rcu_state *rsp;
@ -3907,6 +3911,9 @@ int rcutree_prepare_cpu(unsigned int cpu)
return 0;
}
/*
* Update RCU priority boot kthread affinity for CPU-hotplug changes.
*/
static void rcutree_affinity_setting(unsigned int cpu, int outgoing)
{
struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu);
@ -3914,6 +3921,10 @@ static void rcutree_affinity_setting(unsigned int cpu, int outgoing)
rcu_boost_kthread_setaffinity(rdp->mynode, outgoing);
}
/*
* Near the end of the CPU-online process. Pretty much all services
* enabled, and the CPU is now very much alive.
*/
int rcutree_online_cpu(unsigned int cpu)
{
sync_sched_exp_online_cleanup(cpu);
@ -3921,13 +3932,19 @@ int rcutree_online_cpu(unsigned int cpu)
return 0;
}
/*
* Near the beginning of the process. The CPU is still very much alive
* with pretty much all services enabled.
*/
int rcutree_offline_cpu(unsigned int cpu)
{
rcutree_affinity_setting(cpu, cpu);
return 0;
}
/*
* Near the end of the offline process. We do only tracing here.
*/
int rcutree_dying_cpu(unsigned int cpu)
{
struct rcu_state *rsp;
@ -3937,6 +3954,9 @@ int rcutree_dying_cpu(unsigned int cpu)
return 0;
}
/*
* The outgoing CPU is gone and we are running elsewhere.
*/
int rcutree_dead_cpu(unsigned int cpu)
{
struct rcu_state *rsp;
@ -3954,6 +3974,10 @@ int rcutree_dead_cpu(unsigned int cpu)
* incoming CPUs are not allowed to use RCU read-side critical sections
* until this function is called. Failing to observe this restriction
* will result in lockdep splats.
*
* Note that this function is special in that it is invoked directly
* from the incoming CPU rather than from the cpuhp_step mechanism.
* This is because this function must be invoked at a precise location.
*/
void rcu_cpu_starting(unsigned int cpu)
{
@ -3976,9 +4000,6 @@ void rcu_cpu_starting(unsigned int cpu)
#ifdef CONFIG_HOTPLUG_CPU
/*
* The CPU is exiting the idle loop into the arch_cpu_idle_dead()
* function. We now remove it from the rcu_node tree's ->qsmaskinit
* bit masks.
* The CPU is exiting the idle loop into the arch_cpu_idle_dead()
* function. We now remove it from the rcu_node tree's ->qsmaskinit
* bit masks.
@ -3997,6 +4018,14 @@ static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
/*
* The outgoing function has no further need of RCU, so remove it from
* the list of CPUs that RCU must track.
*
* Note that this function is special in that it is invoked directly
* from the outgoing CPU rather than from the cpuhp_step mechanism.
* This is because this function must be invoked at a precise location.
*/
void rcu_report_dead(unsigned int cpu)
{
struct rcu_state *rsp;
@ -4011,6 +4040,10 @@ void rcu_report_dead(unsigned int cpu)
}
#endif
/*
* On non-huge systems, use expedited RCU grace periods to make suspend
* and hibernation run faster.
*/
static int rcu_pm_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{