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cpu-hotplug: replace per-subsystem mutexes with get_online_cpus() 

This patch converts the known per-subsystem mutexes to get_online_cpus
put_online_cpus. It also eliminates the CPU_LOCK_ACQUIRE and
CPU_LOCK_RELEASE hotplug notification events.

Signed-off-by: Gautham  R Shenoy <ego@in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Gautham R Shenoy 2008-01-25 21:08:02 +01:00 committed by Ingo Molnar
parent 86ef5c9a8e
commit 95402b3829
5 changed files with 36 additions and 50 deletions
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4
include/linux/notifier.h
View File

@ -207,9 +207,7 @@ static inline int notifier_to_errno(int ret)
#define CPU_DOWN_PREPARE 0x0005 /* CPU (unsigned)v going down */
#define CPU_DOWN_FAILED 0x0006 /* CPU (unsigned)v NOT going down */
#define CPU_DEAD 0x0007 /* CPU (unsigned)v dead */
#define CPU_LOCK_ACQUIRE 0x0008 /* Acquire all hotcpu locks */
#define CPU_LOCK_RELEASE 0x0009 /* Release all hotcpu locks */
#define CPU_DYING 0x000A /* CPU (unsigned)v not running any task,
#define CPU_DYING 0x0008 /* CPU (unsigned)v not running any task,
* not handling interrupts, soon dead */
/* Used for CPU hotplug events occuring while tasks are frozen due to a suspend

4
kernel/cpu.c
View File

@ -218,7 +218,6 @@ static int _cpu_down(unsigned int cpu, int tasks_frozen)
return -EINVAL;
cpu_hotplug_begin();
raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
hcpu, -1, &nr_calls);
if (err == NOTIFY_BAD) {
@ -271,7 +270,6 @@ out_thread:
out_allowed:
set_cpus_allowed(current, old_allowed);
out_release:
raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
cpu_hotplug_done();
return err;
}
@ -302,7 +300,6 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
return -EINVAL;
cpu_hotplug_begin();
raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
-1, &nr_calls);
if (ret == NOTIFY_BAD) {
@ -326,7 +323,6 @@ out_notify:
if (ret != 0)
__raw_notifier_call_chain(&cpu_chain,
CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
cpu_hotplug_done();
return ret;

25
kernel/sched.c
View File

@ -439,7 +439,6 @@ struct rq {
};
static DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
static DEFINE_MUTEX(sched_hotcpu_mutex);
static inline void check_preempt_curr(struct rq *rq, struct task_struct *p)
{
@ -4546,13 +4545,13 @@ long sched_setaffinity(pid_t pid, cpumask_t new_mask)
struct task_struct *p;
int retval;
mutex_lock(&sched_hotcpu_mutex);
get_online_cpus();
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
if (!p) {
read_unlock(&tasklist_lock);
mutex_unlock(&sched_hotcpu_mutex);
put_online_cpus();
return -ESRCH;
}
@ -4592,7 +4591,7 @@ long sched_setaffinity(pid_t pid, cpumask_t new_mask)
}
out_unlock:
put_task_struct(p);
mutex_unlock(&sched_hotcpu_mutex);
put_online_cpus();
return retval;
}
@ -4649,7 +4648,7 @@ long sched_getaffinity(pid_t pid, cpumask_t *mask)
struct task_struct *p;
int retval;
mutex_lock(&sched_hotcpu_mutex);
get_online_cpus();
read_lock(&tasklist_lock);
retval = -ESRCH;
@ -4665,7 +4664,7 @@ long sched_getaffinity(pid_t pid, cpumask_t *mask)
out_unlock:
read_unlock(&tasklist_lock);
mutex_unlock(&sched_hotcpu_mutex);
put_online_cpus();
return retval;
}
@ -5625,9 +5624,6 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
struct rq *rq;
switch (action) {
case CPU_LOCK_ACQUIRE:
mutex_lock(&sched_hotcpu_mutex);
break;
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
@ -5697,9 +5693,6 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
spin_unlock_irq(&rq->lock);
break;
#endif
case CPU_LOCK_RELEASE:
mutex_unlock(&sched_hotcpu_mutex);
break;
}
return NOTIFY_OK;
}
@ -6655,10 +6648,10 @@ static int arch_reinit_sched_domains(void)
{
int err;
mutex_lock(&sched_hotcpu_mutex);
get_online_cpus();
detach_destroy_domains(&cpu_online_map);
err = arch_init_sched_domains(&cpu_online_map);
mutex_unlock(&sched_hotcpu_mutex);
put_online_cpus();
return err;
}
@ -6769,12 +6762,12 @@ void __init sched_init_smp(void)
{
cpumask_t non_isolated_cpus;
mutex_lock(&sched_hotcpu_mutex);
get_online_cpus();
arch_init_sched_domains(&cpu_online_map);
cpus_andnot(non_isolated_cpus, cpu_possible_map, cpu_isolated_map);
if (cpus_empty(non_isolated_cpus))
cpu_set(smp_processor_id(), non_isolated_cpus);
mutex_unlock(&sched_hotcpu_mutex);
put_online_cpus();
/* XXX: Theoretical race here - CPU may be hotplugged now */
hotcpu_notifier(update_sched_domains, 0);

35
kernel/workqueue.c
View File

@ -67,9 +67,8 @@ struct workqueue_struct {
#endif
};
/* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
threads to each one as cpus come/go. */
static DEFINE_MUTEX(workqueue_mutex);
/* Serializes the accesses to the list of workqueues. */
static DEFINE_SPINLOCK(workqueue_lock);
static LIST_HEAD(workqueues);
static int singlethread_cpu __read_mostly;
@ -592,8 +591,6 @@ EXPORT_SYMBOL(schedule_delayed_work_on);
* Returns zero on success.
* Returns -ve errno on failure.
*
* Appears to be racy against CPU hotplug.
*
* schedule_on_each_cpu() is very slow.
*/
int schedule_on_each_cpu(work_func_t func)
@ -605,7 +602,7 @@ int schedule_on_each_cpu(work_func_t func)
if (!works)
return -ENOMEM;
preempt_disable(); /* CPU hotplug */
get_online_cpus();
for_each_online_cpu(cpu) {
struct work_struct *work = per_cpu_ptr(works, cpu);
@ -613,8 +610,8 @@ int schedule_on_each_cpu(work_func_t func)
set_bit(WORK_STRUCT_PENDING, work_data_bits(work));
__queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu), work);
}
preempt_enable();
flush_workqueue(keventd_wq);
put_online_cpus();
free_percpu(works);
return 0;
}
@ -750,8 +747,10 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
err = create_workqueue_thread(cwq, singlethread_cpu);
start_workqueue_thread(cwq, -1);
} else {
mutex_lock(&workqueue_mutex);
get_online_cpus();
spin_lock(&workqueue_lock);
list_add(&wq->list, &workqueues);
spin_unlock(&workqueue_lock);
for_each_possible_cpu(cpu) {
cwq = init_cpu_workqueue(wq, cpu);
@ -760,7 +759,7 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
err = create_workqueue_thread(cwq, cpu);
start_workqueue_thread(cwq, cpu);
}
mutex_unlock(&workqueue_mutex);
put_online_cpus();
}
if (err) {
@ -775,7 +774,7 @@ static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
{
/*
* Our caller is either destroy_workqueue() or CPU_DEAD,
* workqueue_mutex protects cwq->thread
* get_online_cpus() protects cwq->thread.
*/
if (cwq->thread == NULL)
return;
@ -810,9 +809,11 @@ void destroy_workqueue(struct workqueue_struct *wq)
struct cpu_workqueue_struct *cwq;
int cpu;
mutex_lock(&workqueue_mutex);
get_online_cpus();
spin_lock(&workqueue_lock);
list_del(&wq->list);
mutex_unlock(&workqueue_mutex);
spin_unlock(&workqueue_lock);
put_online_cpus();
for_each_cpu_mask(cpu, *cpu_map) {
cwq = per_cpu_ptr(wq->cpu_wq, cpu);
@ -835,13 +836,6 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
action &= ~CPU_TASKS_FROZEN;
switch (action) {
case CPU_LOCK_ACQUIRE:
mutex_lock(&workqueue_mutex);
return NOTIFY_OK;
case CPU_LOCK_RELEASE:
mutex_unlock(&workqueue_mutex);
return NOTIFY_OK;
case CPU_UP_PREPARE:
cpu_set(cpu, cpu_populated_map);
@ -854,7 +848,8 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
case CPU_UP_PREPARE:
if (!create_workqueue_thread(cwq, cpu))
break;
printk(KERN_ERR "workqueue for %i failed\n", cpu);
printk(KERN_ERR "workqueue [%s] for %i failed\n",
wq->name, cpu);
return NOTIFY_BAD;
case CPU_ONLINE:

18
mm/slab.c
View File

@ -730,8 +730,7 @@ static inline void init_lock_keys(void)
#endif
/*
* 1. Guard access to the cache-chain.
* 2. Protect sanity of cpu_online_map against cpu hotplug events
* Guard access to the cache-chain.
*/
static DEFINE_MUTEX(cache_chain_mutex);
static struct list_head cache_chain;
@ -1331,12 +1330,11 @@ static int __cpuinit cpuup_callback(struct notifier_block *nfb,
int err = 0;
switch (action) {
case CPU_LOCK_ACQUIRE:
mutex_lock(&cache_chain_mutex);
break;
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
mutex_lock(&cache_chain_mutex);
err = cpuup_prepare(cpu);
mutex_unlock(&cache_chain_mutex);
break;
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
@ -1373,9 +1371,8 @@ static int __cpuinit cpuup_callback(struct notifier_block *nfb,
#endif
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
mutex_lock(&cache_chain_mutex);
cpuup_canceled(cpu);
break;
case CPU_LOCK_RELEASE:
mutex_unlock(&cache_chain_mutex);
break;
}
@ -2170,6 +2167,7 @@ kmem_cache_create (const char *name, size_t size, size_t align,
* We use cache_chain_mutex to ensure a consistent view of
* cpu_online_map as well. Please see cpuup_callback
*/
get_online_cpus();
mutex_lock(&cache_chain_mutex);
list_for_each_entry(pc, &cache_chain, next) {
@ -2396,6 +2394,7 @@ oops:
panic("kmem_cache_create(): failed to create slab `%s'\n",
name);
mutex_unlock(&cache_chain_mutex);
put_online_cpus();
return cachep;
}
EXPORT_SYMBOL(kmem_cache_create);
@ -2547,9 +2546,11 @@ int kmem_cache_shrink(struct kmem_cache *cachep)
int ret;
BUG_ON(!cachep || in_interrupt());
get_online_cpus();
mutex_lock(&cache_chain_mutex);
ret = __cache_shrink(cachep);
mutex_unlock(&cache_chain_mutex);
put_online_cpus();
return ret;
}
EXPORT_SYMBOL(kmem_cache_shrink);
@ -2575,6 +2576,7 @@ void kmem_cache_destroy(struct kmem_cache *cachep)
BUG_ON(!cachep || in_interrupt());
/* Find the cache in the chain of caches. */
get_online_cpus();
mutex_lock(&cache_chain_mutex);
/*
* the chain is never empty, cache_cache is never destroyed
@ -2584,6 +2586,7 @@ void kmem_cache_destroy(struct kmem_cache *cachep)
slab_error(cachep, "Can't free all objects");
list_add(&cachep->next, &cache_chain);
mutex_unlock(&cache_chain_mutex);
put_online_cpus();
return;
}
@ -2592,6 +2595,7 @@ void kmem_cache_destroy(struct kmem_cache *cachep)
__kmem_cache_destroy(cachep);
mutex_unlock(&cache_chain_mutex);
put_online_cpus();
}
EXPORT_SYMBOL(kmem_cache_destroy);