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From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
	akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
	josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
	rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
	fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH v2 tip/core/rcu 07/11] rcu: Improve comments for hotplug/suspend/hibernate functions
Date: Mon, 17 Apr 2017 16:28:54 -0700	[thread overview]
Message-ID: <1492471738-1377-7-git-send-email-paulmck@linux.vnet.ibm.com> (raw)
In-Reply-To: <20170417232714.GA19013@linux.vnet.ibm.com>

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcu/tree.c | 41 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 37 insertions(+), 4 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index bdaa69d23a8a..c4f195dd7c94 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -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)
 {
@@ -3979,9 +4003,6 @@ void rcu_cpu_starting(unsigned int 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.
  */
 static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
 {
@@ -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)
 {
-- 
2.5.2

  parent reply	other threads:[~2017-04-17 23:29 UTC|newest]

Thread overview: 106+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-12 16:54 [PATCH tip/core/rcu 0/13] Miscellaneous fixes for 4.12 Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 01/13] mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU Paul E. McKenney
2017-04-13  9:12   ` Peter Zijlstra
2017-04-13 11:06     ` Vlastimil Babka
2017-04-13 16:00       ` Paul E. McKenney
2017-04-13 16:17       ` Peter Zijlstra
2017-04-13 17:24         ` Paul E. McKenney
2017-04-13 21:30         ` Eric Dumazet
2017-04-14  8:45           ` Peter Zijlstra
2017-04-14 13:39             ` Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 02/13] lockdep: Use "WARNING" tag on lockdep splats Paul E. McKenney
2017-04-13  9:14   ` Peter Zijlstra
2017-04-13 16:01     ` Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 03/13] types: Update obsolete callback_head comment Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 04/13] rcu: Make RCU_FANOUT_LEAF help text more explicit about skew_tick Paul E. McKenney
2017-04-13  9:15   ` Peter Zijlstra
2017-04-13 16:03     ` Paul E. McKenney
2017-04-13 16:19       ` Peter Zijlstra
2017-04-13 16:55         ` Paul E. McKenney
2017-04-13 17:04           ` Peter Zijlstra
2017-04-13 17:31             ` Paul E. McKenney
2017-04-13 17:46               ` Peter Zijlstra
2017-04-13 18:19                 ` Paul E. McKenney
2017-04-13 18:23                   ` Peter Zijlstra
2017-04-13 18:42                     ` Paul E. McKenney
2017-04-19 13:22                       ` Peter Zijlstra
2017-04-19 13:48                         ` Peter Zijlstra
2017-04-19 15:08                           ` Paul E. McKenney
2017-04-19 15:40                             ` Peter Zijlstra
2017-04-19 16:13                               ` Paul E. McKenney
2017-04-19 14:50                         ` Paul E. McKenney
2017-04-13 18:29               ` Peter Zijlstra
2017-04-13 19:42                 ` Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 05/13] rcu: Remove obsolete comment from rcu_future_gp_cleanup() header Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 06/13] hlist_add_tail_rcu disable sparse warning Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 07/13] rcu: Add smp_mb__after_atomic() to sync_exp_work_done() Paul E. McKenney
2017-04-13  9:18   ` Peter Zijlstra
2017-04-13  9:33     ` Peter Zijlstra
2017-04-13 16:10     ` Paul E. McKenney
2017-04-13 16:24       ` Peter Zijlstra
2017-04-13 16:57         ` Paul E. McKenney
2017-04-13 17:10           ` Peter Zijlstra
2017-04-13 17:39             ` Paul E. McKenney
2017-04-13 17:51               ` Peter Zijlstra
2017-04-13 17:59                 ` Peter Zijlstra
2017-04-19 23:24                   ` Paul E. McKenney
2017-04-19 23:23                 ` Paul E. McKenney
2017-04-20 11:17                   ` Peter Zijlstra
2017-04-20 15:03                     ` Paul E. McKenney
2017-04-20 15:08                       ` Peter Zijlstra
2017-06-09 22:56                         ` Paul E. McKenney
2017-06-12 14:51                           ` Dmitry Vyukov
2017-06-12 21:54                             ` Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 08/13] rcu: Improve comments for hotplug/suspend/hibernate functions Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 09/13] mm: Use static initialization for "srcu" Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 10/13] torture: Use correct path for Kconfig fragment for duplicates Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 11/13] rcu: Use bool value directly Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 12/13] rcu: Use true/false in assignment to bool Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 13/13] rcu: Fix typo in PER_RCU_NODE_PERIOD header comment Paul E. McKenney
2017-04-17 23:27 ` [PATCH v2 tip/core/rcu 0/13] Miscellaneous fixes for 4.12 Paul E. McKenney
2017-04-17 23:28   ` [PATCH v2 tip/core/rcu 01/11] mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU Paul E. McKenney
2017-04-18  0:14     ` David Rientjes
2017-04-17 23:28   ` [PATCH v2 tip/core/rcu 02/11] lockdep: Use "WARNING" tag on lockdep splats Paul E. McKenney
2017-04-19 15:00     ` Josh Triplett
2017-04-19 16:26       ` Paul E. McKenney
2017-04-17 23:28   ` [PATCH v2 tip/core/rcu 03/11] types: Update obsolete callback_head comment Paul E. McKenney
2017-04-17 23:28   ` [PATCH v2 tip/core/rcu 04/11] rcu: Make RCU_FANOUT_LEAF help text more explicit about skew_tick Paul E. McKenney
2017-04-18  0:18     ` Josh Triplett
2017-04-18 18:42       ` Paul E. McKenney
2017-04-17 23:28   ` [PATCH v2 tip/core/rcu 05/11] rcu: Remove obsolete comment from rcu_future_gp_cleanup() header Paul E. McKenney
2017-04-17 23:28   ` [PATCH v2 tip/core/rcu 06/11] hlist_add_tail_rcu disable sparse warning Paul E. McKenney
2017-04-17 23:28   ` Paul E. McKenney [this message]
2017-04-17 23:28   ` [PATCH v2 tip/core/rcu 08/11] torture: Use correct path for Kconfig fragment for duplicates Paul E. McKenney
2017-04-17 23:28   ` [PATCH v2 tip/core/rcu 09/11] rcu: Use bool value directly Paul E. McKenney
2017-04-17 23:28   ` [PATCH v2 tip/core/rcu 10/11] rcu: Use true/false in assignment to bool Paul E. McKenney
2017-04-17 23:28   ` [PATCH v2 tip/core/rcu 11/11] rcu: Fix typo in PER_RCU_NODE_PERIOD header comment Paul E. McKenney
2017-04-19 11:28   ` [PATCH v2 tip/core/rcu 0/13] Miscellaneous fixes for 4.12 Peter Zijlstra
2017-04-19 11:35     ` Peter Zijlstra
2017-04-19 11:48     ` Christian Borntraeger
2017-04-19 12:08       ` Peter Zijlstra
2017-04-19 12:51         ` Marc Zyngier
2017-04-19 14:47         ` Paul E. McKenney
2017-04-19 14:52           ` Peter Zijlstra
2017-04-19 15:13             ` Paul E. McKenney
2017-04-19 14:58           ` Josh Triplett
2017-04-19 15:03             ` Peter Zijlstra
2017-04-19 15:17               ` Paul E. McKenney
2017-04-19 13:22       ` Paul E. McKenney
2017-04-19 13:25         ` Christian Borntraeger
2017-04-19 13:02     ` Paul E. McKenney
2017-04-19 13:15       ` Peter Zijlstra
2017-04-19 15:37         ` Paul E. McKenney
2017-04-19 15:43           ` Peter Zijlstra
2017-04-19 16:12             ` Paul E. McKenney
2017-04-19 16:45   ` Paul E. McKenney
2017-04-19 16:46     ` [PATCH v3 tip/core/rcu 01/11] mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU Paul E. McKenney
2017-04-19 16:46     ` [PATCH v3 tip/core/rcu 02/11] lockdep: Use "WARNING" tag on lockdep splats Paul E. McKenney
2017-04-19 16:46     ` [PATCH v3 tip/core/rcu 03/11] types: Update obsolete callback_head comment Paul E. McKenney
2017-04-19 16:46     ` [PATCH v3 tip/core/rcu 04/11] rcu: Make RCU_FANOUT_LEAF help text more explicit about skew_tick Paul E. McKenney
2017-04-19 16:46     ` [PATCH v3 tip/core/rcu 05/11] rcu: Remove obsolete comment from rcu_future_gp_cleanup() header Paul E. McKenney
2017-04-19 16:46     ` [PATCH v3 tip/core/rcu 06/11] hlist_add_tail_rcu disable sparse warning Paul E. McKenney
2017-04-19 16:46     ` [PATCH v3 tip/core/rcu 07/11] rcu: Improve comments for hotplug/suspend/hibernate functions Paul E. McKenney
2017-04-19 16:46     ` [PATCH v3 tip/core/rcu 08/11] torture: Use correct path for Kconfig fragment for duplicates Paul E. McKenney
2017-04-19 16:46     ` [PATCH v3 tip/core/rcu 09/11] rcu: Use bool value directly Paul E. McKenney
2017-04-19 16:46     ` [PATCH v3 tip/core/rcu 10/11] rcu: Use true/false in assignment to bool Paul E. McKenney
2017-04-19 16:46     ` [PATCH v3 tip/core/rcu 11/11] rcu: Fix typo in PER_RCU_NODE_PERIOD header comment Paul E. McKenney

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