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Commit 2e597558086dec36d5c33521a36e0f6b1bc3f3a7

Authored by Paul E. McKenney
Committed by Ingo Molnar
1 parent 799e64f05f

rcu: Simplify RCU CPU-hotplug notification 

Use the new cpu_notifier() API to simplify RCU's CPU-hotplug
notifiers, collapsing down to a single such notifier.

This makes it trivial to provide the notifier-ordering
guarantee that rcu_barrier() depends on.

Also remove redundant open_softirq() calls from Hierarchical
RCU notifier.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: josht@linux.vnet.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: hugh.dickins@tiscali.co.uk
Cc: benh@kernel.crashing.org
LKML-Reference: <12503552312510-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Showing 3 changed files with 22 additions and 36 deletions Side-by-side Diff

... ... @@ -217,9 +217,13 @@
217 217 wake_up(&rcu_migrate_wq);
218 218 }
219 219  
  220 +extern int rcu_cpu_notify(struct notifier_block *self,
  221 + unsigned long action, void *hcpu);
  222 +
220 223 static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,
221 224 unsigned long action, void *hcpu)
222 225 {
  226 + rcu_cpu_notify(self, action, hcpu);
223 227 if (action == CPU_DYING) {
224 228 /*
225 229 * preempt_disable() in on_each_cpu() prevents stop_machine(),
226 230  
... ... @@ -244,8 +248,18 @@
244 248  
245 249 void __init rcu_init(void)
246 250 {
  251 + int i;
  252 +
247 253 __rcu_init();
248   - hotcpu_notifier(rcu_barrier_cpu_hotplug, 0);
  254 + cpu_notifier(rcu_barrier_cpu_hotplug, 0);
  255 +
  256 + /*
  257 + * We don't need protection against CPU-hotplug here because
  258 + * this is called early in boot, before either interrupts
  259 + * or the scheduler are operational.
  260 + */
  261 + for_each_online_cpu(i)
  262 + rcu_barrier_cpu_hotplug(NULL, CPU_UP_PREPARE, (void *)(long)i);
249 263 }
250 264  
251 265 void rcu_scheduler_starting(void)
... ... @@ -1417,8 +1417,8 @@
1417 1417 return 0;
1418 1418 }
1419 1419  
1420   -static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
1421   - unsigned long action, void *hcpu)
  1420 +int __cpuinit rcu_cpu_notify(struct notifier_block *self,
  1421 + unsigned long action, void *hcpu)
1422 1422 {
1423 1423 long cpu = (long)hcpu;
1424 1424  
... ... @@ -1439,10 +1439,6 @@
1439 1439 return NOTIFY_OK;
1440 1440 }
1441 1441  
1442   -static struct notifier_block __cpuinitdata rcu_nb = {
1443   - .notifier_call = rcu_cpu_notify,
1444   -};
1445   -
1446 1442 void __init __rcu_init(void)
1447 1443 {
1448 1444 int cpu;
... ... @@ -1471,23 +1467,6 @@
1471 1467 rdp->waitschedtail = &rdp->waitschedlist;
1472 1468 rdp->rcu_sched_sleeping = 0;
1473 1469 }
1474   - register_cpu_notifier(&rcu_nb);
1475   -
1476   - /*
1477   - * We don't need protection against CPU-Hotplug here
1478   - * since
1479   - * a) If a CPU comes online while we are iterating over the
1480   - * cpu_online_mask below, we would only end up making a
1481   - * duplicate call to rcu_online_cpu() which sets the corresponding
1482   - * CPU's mask in the rcu_cpu_online_map.
1483   - *
1484   - * b) A CPU cannot go offline at this point in time since the user
1485   - * does not have access to the sysfs interface, nor do we
1486   - * suspend the system.
1487   - */
1488   - for_each_online_cpu(cpu)
1489   - rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long) cpu);
1490   -
1491 1470 open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
1492 1471 }
1493 1472  
... ... @@ -1132,6 +1132,8 @@
1132 1132 {
1133 1133 unsigned long flags;
1134 1134  
  1135 + WARN_ON_ONCE(rdp->beenonline == 0);
  1136 +
1135 1137 /*
1136 1138 * If an RCU GP has gone long enough, go check for dyntick
1137 1139 * idle CPUs and, if needed, send resched IPIs.
1138 1140  
... ... @@ -1416,14 +1418,13 @@
1416 1418 {
1417 1419 rcu_init_percpu_data(cpu, &rcu_state);
1418 1420 rcu_init_percpu_data(cpu, &rcu_bh_state);
1419   - open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
1420 1421 }
1421 1422  
1422 1423 /*
1423 1424 * Handle CPU online/offline notifcation events.
1424 1425 */
1425   -static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
1426   - unsigned long action, void *hcpu)
  1426 +int __cpuinit rcu_cpu_notify(struct notifier_block *self,
  1427 + unsigned long action, void *hcpu)
1427 1428 {
1428 1429 long cpu = (long)hcpu;
1429 1430  
... ... @@ -1532,10 +1533,6 @@
1532 1533 } \
1533 1534 } while (0)
1534 1535  
1535   -static struct notifier_block __cpuinitdata rcu_nb = {
1536   - .notifier_call = rcu_cpu_notify,
1537   -};
1538   -
1539 1536 void __init __rcu_init(void)
1540 1537 {
1541 1538 int i; /* All used by RCU_DATA_PTR_INIT(). */
... ... @@ -1554,11 +1551,7 @@
1554 1551 RCU_DATA_PTR_INIT(&rcu_bh_state, rcu_bh_data);
1555 1552 for_each_possible_cpu(i)
1556 1553 rcu_boot_init_percpu_data(i, &rcu_bh_state);
1557   -
1558   - for_each_online_cpu(i)
1559   - rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long)i);
1560   - /* Register notifier for non-boot CPUs */
1561   - register_cpu_notifier(&rcu_nb);
  1554 + open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
1562 1555 }
1563 1556  
1564 1557 module_param(blimit, int, 0);