Commit 86ef5c9a authored by Gautham R Shenoy's avatar Gautham R Shenoy Committed by Ingo Molnar

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: default avatarGautham R Shenoy <ego@in.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent d221938c
......@@ -109,12 +109,13 @@ Never use anything other than cpumask_t to represent bitmap of CPUs.
for_each_cpu_mask(x,mask) - Iterate over some random collection of cpu mask.
#include <linux/cpu.h>
lock_cpu_hotplug() and unlock_cpu_hotplug():
get_online_cpus() and put_online_cpus():
The above calls are used to inhibit cpu hotplug operations. While holding the
cpucontrol mutex, cpu_online_map will not change. If you merely need to avoid
cpus going away, you could also use preempt_disable() and preempt_enable()
for those sections. Just remember the critical section cannot call any
The above calls are used to inhibit cpu hotplug operations. While the
cpu_hotplug.refcount is non zero, the cpu_online_map will not change.
If you merely need to avoid cpus going away, you could also use
preempt_disable() and preempt_enable() for those sections.
Just remember the critical section cannot call any
function that can sleep or schedule this process away. The preempt_disable()
will work as long as stop_machine_run() is used to take a cpu down.
......
......@@ -58,13 +58,13 @@ asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len,
if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask)))
return -EFAULT;
lock_cpu_hotplug();
get_online_cpus();
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
if (!p) {
read_unlock(&tasklist_lock);
unlock_cpu_hotplug();
put_online_cpus();
return -ESRCH;
}
......@@ -106,7 +106,7 @@ asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len,
out_unlock:
put_task_struct(p);
unlock_cpu_hotplug();
put_online_cpus();
return retval;
}
......@@ -125,7 +125,7 @@ asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
if (len < real_len)
return -EINVAL;
lock_cpu_hotplug();
get_online_cpus();
read_lock(&tasklist_lock);
retval = -ESRCH;
......@@ -140,7 +140,7 @@ asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
out_unlock:
read_unlock(&tasklist_lock);
unlock_cpu_hotplug();
put_online_cpus();
if (retval)
return retval;
if (copy_to_user(user_mask_ptr, &mask, real_len))
......
......@@ -153,7 +153,7 @@ static int pseries_add_processor(struct device_node *np)
for (i = 0; i < nthreads; i++)
cpu_set(i, tmp);
lock_cpu_hotplug();
cpu_maps_update_begin();
BUG_ON(!cpus_subset(cpu_present_map, cpu_possible_map));
......@@ -190,7 +190,7 @@ static int pseries_add_processor(struct device_node *np)
}
err = 0;
out_unlock:
unlock_cpu_hotplug();
cpu_maps_update_done();
return err;
}
......@@ -211,7 +211,7 @@ static void pseries_remove_processor(struct device_node *np)
nthreads = len / sizeof(u32);
lock_cpu_hotplug();
cpu_maps_update_begin();
for (i = 0; i < nthreads; i++) {
for_each_present_cpu(cpu) {
if (get_hard_smp_processor_id(cpu) != intserv[i])
......@@ -225,7 +225,7 @@ static void pseries_remove_processor(struct device_node *np)
printk(KERN_WARNING "Could not find cpu to remove "
"with physical id 0x%x\n", intserv[i]);
}
unlock_cpu_hotplug();
cpu_maps_update_done();
}
static int pseries_smp_notifier(struct notifier_block *nb,
......
......@@ -382,7 +382,7 @@ static void do_event_scan_all_cpus(long delay)
{
int cpu;
lock_cpu_hotplug();
get_online_cpus();
cpu = first_cpu(cpu_online_map);
for (;;) {
set_cpus_allowed(current, cpumask_of_cpu(cpu));
......@@ -390,15 +390,15 @@ static void do_event_scan_all_cpus(long delay)
set_cpus_allowed(current, CPU_MASK_ALL);
/* Drop hotplug lock, and sleep for the specified delay */
unlock_cpu_hotplug();
put_online_cpus();
msleep_interruptible(delay);
lock_cpu_hotplug();
get_online_cpus();
cpu = next_cpu(cpu, cpu_online_map);
if (cpu == NR_CPUS)
break;
}
unlock_cpu_hotplug();
put_online_cpus();
}
static int rtasd(void *unused)
......
......@@ -349,7 +349,7 @@ int mtrr_add_page(unsigned long base, unsigned long size,
replace = -1;
/* No CPU hotplug when we change MTRR entries */
lock_cpu_hotplug();
get_online_cpus();
/* Search for existing MTRR */
mutex_lock(&mtrr_mutex);
for (i = 0; i < num_var_ranges; ++i) {
......@@ -405,7 +405,7 @@ int mtrr_add_page(unsigned long base, unsigned long size,
error = i;
out:
mutex_unlock(&mtrr_mutex);
unlock_cpu_hotplug();
put_online_cpus();
return error;
}
......@@ -495,7 +495,7 @@ int mtrr_del_page(int reg, unsigned long base, unsigned long size)
max = num_var_ranges;
/* No CPU hotplug when we change MTRR entries */
lock_cpu_hotplug();
get_online_cpus();
mutex_lock(&mtrr_mutex);
if (reg < 0) {
/* Search for existing MTRR */
......@@ -536,7 +536,7 @@ int mtrr_del_page(int reg, unsigned long base, unsigned long size)
error = reg;
out:
mutex_unlock(&mtrr_mutex);
unlock_cpu_hotplug();
put_online_cpus();
return error;
}
/**
......
......@@ -436,7 +436,7 @@ static ssize_t microcode_write (struct file *file, const char __user *buf, size_
return -EINVAL;
}
lock_cpu_hotplug();
get_online_cpus();
mutex_lock(&microcode_mutex);
user_buffer = (void __user *) buf;
......@@ -447,7 +447,7 @@ static ssize_t microcode_write (struct file *file, const char __user *buf, size_
ret = (ssize_t)len;
mutex_unlock(&microcode_mutex);
unlock_cpu_hotplug();
put_online_cpus();
return ret;
}
......@@ -658,14 +658,14 @@ static ssize_t reload_store(struct sys_device *dev, const char *buf, size_t sz)
old = current->cpus_allowed;
lock_cpu_hotplug();
get_online_cpus();
set_cpus_allowed(current, cpumask_of_cpu(cpu));
mutex_lock(&microcode_mutex);
if (uci->valid)
err = cpu_request_microcode(cpu);
mutex_unlock(&microcode_mutex);
unlock_cpu_hotplug();
put_online_cpus();
set_cpus_allowed(current, old);
}
if (err)
......@@ -817,9 +817,9 @@ static int __init microcode_init (void)
return PTR_ERR(microcode_pdev);
}
lock_cpu_hotplug();
get_online_cpus();
error = sysdev_driver_register(&cpu_sysdev_class, &mc_sysdev_driver);
unlock_cpu_hotplug();
put_online_cpus();
if (error) {
microcode_dev_exit();
platform_device_unregister(microcode_pdev);
......@@ -839,9 +839,9 @@ static void __exit microcode_exit (void)
unregister_hotcpu_notifier(&mc_cpu_notifier);
lock_cpu_hotplug();
get_online_cpus();
sysdev_driver_unregister(&cpu_sysdev_class, &mc_sysdev_driver);
unlock_cpu_hotplug();
put_online_cpus();
platform_device_unregister(microcode_pdev);
}
......
......@@ -459,7 +459,7 @@ void __init lguest_arch_host_init(void)
/* We don't need the complexity of CPUs coming and going while we're
* doing this. */
lock_cpu_hotplug();
get_online_cpus();
if (cpu_has_pge) { /* We have a broader idea of "global". */
/* Remember that this was originally set (for cleanup). */
cpu_had_pge = 1;
......@@ -469,20 +469,20 @@ void __init lguest_arch_host_init(void)
/* Turn off the feature in the global feature set. */
clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
}
unlock_cpu_hotplug();
put_online_cpus();
};
/*:*/
void __exit lguest_arch_host_fini(void)
{
/* If we had PGE before we started, turn it back on now. */
lock_cpu_hotplug();
get_online_cpus();
if (cpu_had_pge) {
set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
/* adjust_pge's argument "1" means set PGE. */
on_each_cpu(adjust_pge, (void *)1, 0, 1);
}
unlock_cpu_hotplug();
put_online_cpus();
}
......
......@@ -29,12 +29,12 @@ static void sclp_cpu_capability_notify(struct work_struct *work)
struct sys_device *sysdev;
printk(KERN_WARNING TAG "cpu capability changed.\n");
lock_cpu_hotplug();
get_online_cpus();
for_each_online_cpu(cpu) {
sysdev = get_cpu_sysdev(cpu);
kobject_uevent(&sysdev->kobj, KOBJ_CHANGE);
}
unlock_cpu_hotplug();
put_online_cpus();
}
static void sclp_conf_receiver_fn(struct evbuf_header *evbuf)
......
......@@ -100,8 +100,8 @@ static inline void cpuhotplug_mutex_unlock(struct mutex *cpu_hp_mutex)
mutex_unlock(cpu_hp_mutex);
}
extern void lock_cpu_hotplug(void);
extern void unlock_cpu_hotplug(void);
extern void get_online_cpus(void);
extern void put_online_cpus(void);
#define hotcpu_notifier(fn, pri) { \
static struct notifier_block fn##_nb = \
{ .notifier_call = fn, .priority = pri }; \
......@@ -118,8 +118,8 @@ static inline void cpuhotplug_mutex_lock(struct mutex *cpu_hp_mutex)
static inline void cpuhotplug_mutex_unlock(struct mutex *cpu_hp_mutex)
{ }
#define lock_cpu_hotplug() do { } while (0)
#define unlock_cpu_hotplug() do { } while (0)
#define get_online_cpus() do { } while (0)
#define put_online_cpus() do { } while (0)
#define hotcpu_notifier(fn, pri) do { (void)(fn); } while (0)
/* These aren't inline functions due to a GCC bug. */
#define register_hotcpu_notifier(nb) ({ (void)(nb); 0; })
......
......@@ -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)
......
......@@ -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.
*/
......
......@@ -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
......
......@@ -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;
......
......@@ -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;
}
......
......@@ -293,7 +293,7 @@ void flow_cache_flush(void)
static DEFINE_MUTEX(flow_flush_sem);
/* Don't want cpus going down or up during this. */
lock_cpu_hotplug();
get_online_cpus();
mutex_lock(&flow_flush_sem);
atomic_set(&info.cpuleft, num_online_cpus());
init_completion(&info.completion);
......@@ -305,7 +305,7 @@ void flow_cache_flush(void)
wait_for_completion(&info.completion);
mutex_unlock(&flow_flush_sem);
unlock_cpu_hotplug();
put_online_cpus();
}
static void __devinit flow_cache_cpu_prepare(int cpu)
......
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