[PATCH -tip] Simplify RCU CPU-hotplug notification
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[PATCH -tip] Simplify RCU CPU-hotplug notification
by Paul E. McKenney-2
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Simplify RCU's CPU-hotplug notifiers so that there is only one notifier.
This makes it trivial to provide the ordering guarantee that rcu_barrier() depends on. This change also allows rcu_barrier() to rely on locking wholly contained in _cpu_down(), rather than that of its callers, making the locking more straightforward. Signed-off-by: Paul E. McKenney <paulmck@...> --- rcupdate.c | 8 ++++++-- rcupreempt.c | 22 +++++----------------- rcutree.c | 18 +++++++++--------- 3 files changed, 20 insertions(+), 28 deletions(-) diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index eae29c2..3fea910 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -217,9 +217,13 @@ static void rcu_migrate_callback(struct rcu_head *notused) wake_up(&rcu_migrate_wq); } +extern int rcu_cpu_notify(struct notifier_block *self, + unsigned long action, void *hcpu); + static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self, unsigned long action, void *hcpu) { + rcu_cpu_notify(self, action, hcpu); if (action == CPU_DYING) { /* * preempt_disable() in on_each_cpu() prevents stop_machine(), @@ -234,7 +238,7 @@ static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self, call_rcu_bh(rcu_migrate_head, rcu_migrate_callback); call_rcu_sched(rcu_migrate_head + 1, rcu_migrate_callback); call_rcu(rcu_migrate_head + 2, rcu_migrate_callback); - } else if (action == CPU_POST_DEAD) { + } else if (action == CPU_DEAD) { /* rcu_migrate_head is protected by cpu_add_remove_lock */ wait_migrated_callbacks(); } @@ -244,8 +248,8 @@ static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self, void __init rcu_init(void) { - __rcu_init(); hotcpu_notifier(rcu_barrier_cpu_hotplug, 0); + __rcu_init(); } void rcu_scheduler_starting(void) diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c index beb0e65..4300212 100644 --- a/kernel/rcupreempt.c +++ b/kernel/rcupreempt.c @@ -1417,7 +1417,7 @@ int rcu_pending(int cpu) return 0; } -static int __cpuinit rcu_cpu_notify(struct notifier_block *self, +int __cpuinit rcu_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) { long cpu = (long)hcpu; @@ -1439,10 +1439,6 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self, return NOTIFY_OK; } -static struct notifier_block __cpuinitdata rcu_nb = { - .notifier_call = rcu_cpu_notify, -}; - void __init __rcu_init(void) { int cpu; @@ -1471,22 +1467,14 @@ void __init __rcu_init(void) rdp->waitschedtail = &rdp->waitschedlist; rdp->rcu_sched_sleeping = 0; } - register_cpu_notifier(&rcu_nb); /* - * We don't need protection against CPU-Hotplug here - * since - * a) If a CPU comes online while we are iterating over the - * cpu_online_mask below, we would only end up making a - * duplicate call to rcu_online_cpu() which sets the corresponding - * CPU's mask in the rcu_cpu_online_map. - * - * b) A CPU cannot go offline at this point in time since the user - * does not have access to the sysfs interface, nor do we - * suspend the system. + * We don't need protection against CPU-hotplug here because + * this is called early in boot, before either interrupts + * or the scheduler are operational. */ for_each_online_cpu(cpu) - rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long) cpu); + rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long) cpu); open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); } diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 7717b95..e8e9e93 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1407,13 +1407,12 @@ static void __cpuinit rcu_online_cpu(int cpu) { rcu_init_percpu_data(cpu, &rcu_state); rcu_init_percpu_data(cpu, &rcu_bh_state); - open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); } /* * Handle CPU online/offline notifcation events. */ -static int __cpuinit rcu_cpu_notify(struct notifier_block *self, +int __cpuinit rcu_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) { long cpu = (long)hcpu; @@ -1523,10 +1522,6 @@ do { \ } \ } while (0) -static struct notifier_block __cpuinitdata rcu_nb = { - .notifier_call = rcu_cpu_notify, -}; - void __init __rcu_init(void) { int i; /* All used by RCU_DATA_PTR_INIT(). */ @@ -1542,10 +1537,15 @@ void __init __rcu_init(void) rcu_init_one(&rcu_bh_state); RCU_DATA_PTR_INIT(&rcu_bh_state, rcu_bh_data); + /* + * We don't need protection against CPU-hotplug here because + * this is called early in boot, before either interrupts + * or the scheduler are operational. + */ for_each_online_cpu(i) - rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long)i); - /* Register notifier for non-boot CPUs */ - register_cpu_notifier(&rcu_nb); + rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)i); + + open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); } module_param(blimit, int, 0); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@... More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |
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[tip:core/rcu] rcu: Simplify RCU CPU-hotplug notification
by Paul E. McKenney-2
::
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Commit-ID: 7fe616c5dd50a50f334edec1ea0580b90b7af0d9
Gitweb: http://git.kernel.org/tip/7fe616c5dd50a50f334edec1ea0580b90b7af0d9 Author: Paul E. McKenney <paulmck@...> AuthorDate: Thu, 9 Jul 2009 17:48:28 -0700 Committer: Ingo Molnar <mingo@...> CommitDate: Tue, 14 Jul 2009 08:16:52 +0200 rcu: Simplify RCU CPU-hotplug notification Simplify RCU's CPU-hotplug notifiers so that there is only one notifier. This makes it trivial to provide the ordering guarantee that rcu_barrier() depends on. This change also allows rcu_barrier() to rely on locking wholly contained in _cpu_down(), rather than that of its callers, making the locking more straightforward. Signed-off-by: Paul E. McKenney <paulmck@...> Cc: laijs@... Cc: dipankar@... LKML-Reference: <20090710004828.GA19385@...> Signed-off-by: Ingo Molnar <mingo@...> --- kernel/rcupdate.c | 8 ++++++-- kernel/rcupreempt.c | 22 +++++----------------- kernel/rcutree.c | 18 +++++++++--------- 3 files changed, 20 insertions(+), 28 deletions(-) diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index eae29c2..3fea910 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -217,9 +217,13 @@ static void rcu_migrate_callback(struct rcu_head *notused) wake_up(&rcu_migrate_wq); } +extern int rcu_cpu_notify(struct notifier_block *self, + unsigned long action, void *hcpu); + static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self, unsigned long action, void *hcpu) { + rcu_cpu_notify(self, action, hcpu); if (action == CPU_DYING) { /* * preempt_disable() in on_each_cpu() prevents stop_machine(), @@ -234,7 +238,7 @@ static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self, call_rcu_bh(rcu_migrate_head, rcu_migrate_callback); call_rcu_sched(rcu_migrate_head + 1, rcu_migrate_callback); call_rcu(rcu_migrate_head + 2, rcu_migrate_callback); - } else if (action == CPU_POST_DEAD) { + } else if (action == CPU_DEAD) { /* rcu_migrate_head is protected by cpu_add_remove_lock */ wait_migrated_callbacks(); } @@ -244,8 +248,8 @@ static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self, void __init rcu_init(void) { - __rcu_init(); hotcpu_notifier(rcu_barrier_cpu_hotplug, 0); + __rcu_init(); } void rcu_scheduler_starting(void) diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c index beb0e65..4300212 100644 --- a/kernel/rcupreempt.c +++ b/kernel/rcupreempt.c @@ -1417,7 +1417,7 @@ int rcu_pending(int cpu) return 0; } -static int __cpuinit rcu_cpu_notify(struct notifier_block *self, +int __cpuinit rcu_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) { long cpu = (long)hcpu; @@ -1439,10 +1439,6 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self, return NOTIFY_OK; } -static struct notifier_block __cpuinitdata rcu_nb = { - .notifier_call = rcu_cpu_notify, -}; - void __init __rcu_init(void) { int cpu; @@ -1471,22 +1467,14 @@ void __init __rcu_init(void) rdp->waitschedtail = &rdp->waitschedlist; rdp->rcu_sched_sleeping = 0; } - register_cpu_notifier(&rcu_nb); /* - * We don't need protection against CPU-Hotplug here - * since - * a) If a CPU comes online while we are iterating over the - * cpu_online_mask below, we would only end up making a - * duplicate call to rcu_online_cpu() which sets the corresponding - * CPU's mask in the rcu_cpu_online_map. - * - * b) A CPU cannot go offline at this point in time since the user - * does not have access to the sysfs interface, nor do we - * suspend the system. + * We don't need protection against CPU-hotplug here because + * this is called early in boot, before either interrupts + * or the scheduler are operational. */ for_each_online_cpu(cpu) - rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long) cpu); + rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long) cpu); open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); } diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 7717b95..e8e9e93 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1407,13 +1407,12 @@ static void __cpuinit rcu_online_cpu(int cpu) { rcu_init_percpu_data(cpu, &rcu_state); rcu_init_percpu_data(cpu, &rcu_bh_state); - open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); } /* * Handle CPU online/offline notifcation events. */ -static int __cpuinit rcu_cpu_notify(struct notifier_block *self, +int __cpuinit rcu_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) { long cpu = (long)hcpu; @@ -1523,10 +1522,6 @@ do { \ } \ } while (0) -static struct notifier_block __cpuinitdata rcu_nb = { - .notifier_call = rcu_cpu_notify, -}; - void __init __rcu_init(void) { int i; /* All used by RCU_DATA_PTR_INIT(). */ @@ -1542,10 +1537,15 @@ void __init __rcu_init(void) rcu_init_one(&rcu_bh_state); RCU_DATA_PTR_INIT(&rcu_bh_state, rcu_bh_data); + /* + * We don't need protection against CPU-hotplug here because + * this is called early in boot, before either interrupts + * or the scheduler are operational. + */ for_each_online_cpu(i) - rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long)i); - /* Register notifier for non-boot CPUs */ - register_cpu_notifier(&rcu_nb); + rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)i); + + open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); } module_param(blimit, int, 0); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@... More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |
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