From 86ef5c9a8edd78e6bf92879f32329d89b2d55b5a Mon Sep 17 00:00:00 2001 From: Gautham R Shenoy Date: Fri, 25 Jan 2008 21:08:02 +0100 Subject: cpu-hotplug: replace lock_cpu_hotplug() with get_online_cpus() Replace all lock_cpu_hotplug/unlock_cpu_hotplug from the kernel and use get_online_cpus and put_online_cpus instead as it highlights the refcount semantics in these operations. The new API guarantees protection against the cpu-hotplug operation, but it doesn't guarantee serialized access to any of the local data structures. Hence the changes needs to be reviewed. In case of pseries_add_processor/pseries_remove_processor, use cpu_maps_update_begin()/cpu_maps_update_done() as we're modifying the cpu_present_map there. Signed-off-by: Gautham R Shenoy Signed-off-by: Ingo Molnar --- kernel/cpu.c | 10 +++++----- kernel/cpuset.c | 14 +++++++------- kernel/rcutorture.c | 6 +++--- kernel/sched.c | 4 ++-- kernel/stop_machine.c | 4 ++-- 5 files changed, 19 insertions(+), 19 deletions(-) (limited to 'kernel') diff --git a/kernel/cpu.c b/kernel/cpu.c index 656dc3fcbbae..b0c4152995f8 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -48,7 +48,7 @@ void __init cpu_hotplug_init(void) #ifdef CONFIG_HOTPLUG_CPU -void lock_cpu_hotplug(void) +void get_online_cpus(void) { might_sleep(); if (cpu_hotplug.active_writer == current) @@ -58,9 +58,9 @@ void lock_cpu_hotplug(void) mutex_unlock(&cpu_hotplug.lock); } -EXPORT_SYMBOL_GPL(lock_cpu_hotplug); +EXPORT_SYMBOL_GPL(get_online_cpus); -void unlock_cpu_hotplug(void) +void put_online_cpus(void) { if (cpu_hotplug.active_writer == current) return; @@ -73,7 +73,7 @@ void unlock_cpu_hotplug(void) mutex_unlock(&cpu_hotplug.lock); } -EXPORT_SYMBOL_GPL(unlock_cpu_hotplug); +EXPORT_SYMBOL_GPL(put_online_cpus); #endif /* CONFIG_HOTPLUG_CPU */ @@ -110,7 +110,7 @@ void cpu_maps_update_done(void) * non zero and goes to sleep again. * * However, this is very difficult to achieve in practice since - * lock_cpu_hotplug() not an api which is called all that often. + * get_online_cpus() not an api which is called all that often. * */ static void cpu_hotplug_begin(void) diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 50f5dc463688..cfaf6419d817 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -537,10 +537,10 @@ static int cpusets_overlap(struct cpuset *a, struct cpuset *b) * * Call with cgroup_mutex held. May take callback_mutex during * call due to the kfifo_alloc() and kmalloc() calls. May nest - * a call to the lock_cpu_hotplug()/unlock_cpu_hotplug() pair. + * a call to the get_online_cpus()/put_online_cpus() pair. * Must not be called holding callback_mutex, because we must not - * call lock_cpu_hotplug() while holding callback_mutex. Elsewhere - * the kernel nests callback_mutex inside lock_cpu_hotplug() calls. + * call get_online_cpus() while holding callback_mutex. Elsewhere + * the kernel nests callback_mutex inside get_online_cpus() calls. * So the reverse nesting would risk an ABBA deadlock. * * The three key local variables below are: @@ -691,9 +691,9 @@ restart: rebuild: /* Have scheduler rebuild sched domains */ - lock_cpu_hotplug(); + get_online_cpus(); partition_sched_domains(ndoms, doms); - unlock_cpu_hotplug(); + put_online_cpus(); done: if (q && !IS_ERR(q)) @@ -1617,10 +1617,10 @@ static struct cgroup_subsys_state *cpuset_create( * * If the cpuset being removed has its flag 'sched_load_balance' * enabled, then simulate turning sched_load_balance off, which - * will call rebuild_sched_domains(). The lock_cpu_hotplug() + * will call rebuild_sched_domains(). The get_online_cpus() * call in rebuild_sched_domains() must not be made while holding * callback_mutex. Elsewhere the kernel nests callback_mutex inside - * lock_cpu_hotplug() calls. So the reverse nesting would risk an + * get_online_cpus() calls. So the reverse nesting would risk an * ABBA deadlock. */ diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c index c3e165c2318f..fd599829e72a 100644 --- a/kernel/rcutorture.c +++ b/kernel/rcutorture.c @@ -726,11 +726,11 @@ static void rcu_torture_shuffle_tasks(void) cpumask_t tmp_mask = CPU_MASK_ALL; int i; - lock_cpu_hotplug(); + get_online_cpus(); /* No point in shuffling if there is only one online CPU (ex: UP) */ if (num_online_cpus() == 1) { - unlock_cpu_hotplug(); + put_online_cpus(); return; } @@ -762,7 +762,7 @@ static void rcu_torture_shuffle_tasks(void) else rcu_idle_cpu--; - unlock_cpu_hotplug(); + put_online_cpus(); } /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the diff --git a/kernel/sched.c b/kernel/sched.c index 86e55a9c2de6..672aa68bfeac 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -7152,7 +7152,7 @@ static int load_balance_monitor(void *unused) int i, cpu, balanced = 1; /* Prevent cpus going down or coming up */ - lock_cpu_hotplug(); + get_online_cpus(); /* lockout changes to doms_cur[] array */ lock_doms_cur(); /* @@ -7186,7 +7186,7 @@ static int load_balance_monitor(void *unused) rcu_read_unlock(); unlock_doms_cur(); - unlock_cpu_hotplug(); + put_online_cpus(); if (!balanced) timeout = sysctl_sched_min_bal_int_shares; diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 319821ef78af..51b5ee53571a 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -203,13 +203,13 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu) int ret; /* No CPUs can come up or down during this. */ - lock_cpu_hotplug(); + get_online_cpus(); p = __stop_machine_run(fn, data, cpu); if (!IS_ERR(p)) ret = kthread_stop(p); else ret = PTR_ERR(p); - unlock_cpu_hotplug(); + put_online_cpus(); return ret; } -- cgit v1.2.3