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Subject[RFC PATCH v3 24/28] CPU: introduce busy flag to temporarily disable CPU online sysfs interface
Date
When doing physical processor hotplug, all affected CPUs need to be
handled in atomic and shouldn't be disturbed by online/offline requests
from CPU device's online sysfs interface. So introduce a busy flag
into struct cpu to temporariliy reject requests from online sysfs
interface.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
---
arch/ia64/include/asm/cpu.h | 2 +-
arch/ia64/kernel/topology.c | 15 +++++++++------
arch/x86/include/asm/cpu.h | 2 +-
arch/x86/kernel/topology.c | 10 ++++++----
drivers/acpi/processor_driver.c | 2 +-
drivers/base/cpu.c | 22 ++++++++++++++++++++++
drivers/xen/cpu_hotplug.c | 2 +-
include/linux/cpu.h | 2 ++
8 files changed, 43 insertions(+), 14 deletions(-)

diff --git a/arch/ia64/include/asm/cpu.h b/arch/ia64/include/asm/cpu.h
index fcca30b..192fa2f 100644
--- a/arch/ia64/include/asm/cpu.h
+++ b/arch/ia64/include/asm/cpu.h
@@ -15,7 +15,7 @@ DECLARE_PER_CPU(struct ia64_cpu, cpu_devices);
DECLARE_PER_CPU(int, cpu_state);

#ifdef CONFIG_HOTPLUG_CPU
-extern int arch_register_cpu(int num);
+extern int arch_register_cpu(int num, int busy);
extern void arch_unregister_cpu(int);
#endif

diff --git a/arch/ia64/kernel/topology.c b/arch/ia64/kernel/topology.c
index c64460b..54a6dfc 100644
--- a/arch/ia64/kernel/topology.c
+++ b/arch/ia64/kernel/topology.c
@@ -40,15 +40,17 @@ EXPORT_SYMBOL_GPL(arch_fix_phys_package_id);


#ifdef CONFIG_HOTPLUG_CPU
-int __ref arch_register_cpu(int num)
+int __ref arch_register_cpu(int num, int busy)
{
#ifdef CONFIG_ACPI
/*
* If CPEI can be re-targeted or if this is not
* CPEI target, then it is hotpluggable
*/
- if (can_cpei_retarget() || !is_cpu_cpei_target(num))
+ if (can_cpei_retarget() || !is_cpu_cpei_target(num)) {
sysfs_cpus[num].cpu.hotpluggable = 1;
+ sysfs_cpus[num].cpu.busy = busy;
+ }
map_cpu_to_node(num, node_cpuid[num].nid);
#endif
return register_cpu(&sysfs_cpus[num].cpu, num);
@@ -64,7 +66,7 @@ void __ref arch_unregister_cpu(int num)
}
EXPORT_SYMBOL(arch_unregister_cpu);
#else
-static int __init arch_register_cpu(int num)
+static int __init arch_register_cpu(int num, int busy)
{
return register_cpu(&sysfs_cpus[num].cpu, num);
}
@@ -90,10 +92,11 @@ static int __init topology_init(void)
panic("kzalloc in topology_init failed - NR_CPUS too big?");

for_each_present_cpu(i) {
- if((err = arch_register_cpu(i)))
- goto out;
+ err = arch_register_cpu(i, 0);
+ if (err)
+ break;
}
-out:
+
return err;
}

diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index 4564c8e..724c777 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -26,7 +26,7 @@ struct x86_cpu {
};

#ifdef CONFIG_HOTPLUG_CPU
-extern int arch_register_cpu(int num);
+extern int arch_register_cpu(int num, int busy);
extern void arch_unregister_cpu(int);
#endif

diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
index 76ee977..c66ef53 100644
--- a/arch/x86/kernel/topology.c
+++ b/arch/x86/kernel/topology.c
@@ -35,7 +35,7 @@
static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);

#ifdef CONFIG_HOTPLUG_CPU
-int __ref arch_register_cpu(int num)
+int __ref arch_register_cpu(int num, int busy)
{
/*
* CPU0 cannot be offlined due to several
@@ -46,8 +46,10 @@ int __ref arch_register_cpu(int num)
* Also certain PCI quirks require not to enable hotplug control
* for all CPU's.
*/
- if (num)
+ if (num) {
per_cpu(cpu_devices, num).cpu.hotpluggable = 1;
+ per_cpu(cpu_devices, num).cpu.busy = busy;
+ }

return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
}
@@ -60,7 +62,7 @@ void arch_unregister_cpu(int num)
EXPORT_SYMBOL(arch_unregister_cpu);
#else /* CONFIG_HOTPLUG_CPU */

-static int __init arch_register_cpu(int num)
+static int __init arch_register_cpu(int num, int busy)
{
return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
}
@@ -76,7 +78,7 @@ static int __init topology_init(void)
#endif

for_each_present_cpu(i)
- arch_register_cpu(i);
+ arch_register_cpu(i, 0);

return 0;
}
diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
index 25079ca..447bd6d 100644
--- a/drivers/acpi/processor_driver.c
+++ b/drivers/acpi/processor_driver.c
@@ -702,7 +702,7 @@ static int acpi_processor_pre_configure(struct acpi_device *device,
if (result)
goto out_unlock;
BUG_ON((pr->id >= nr_cpu_ids) || (pr->id < 0));
- result = arch_register_cpu(pr->id);
+ result = arch_register_cpu(pr->id, 0);
if (result)
goto out_unmap;

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 6345294..dc6246c 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -42,6 +42,11 @@ static ssize_t __ref store_online(struct device *dev,
ssize_t ret;

cpu_hotplug_driver_lock();
+ if (cpu->busy) {
+ ret = -EBUSY;
+ goto out;
+ }
+
switch (buf[0]) {
case '0':
ret = cpu_down(cpu->dev.id);
@@ -56,6 +61,8 @@ static ssize_t __ref store_online(struct device *dev,
default:
ret = -EINVAL;
}
+
+out:
cpu_hotplug_driver_unlock();

if (ret >= 0)
@@ -308,6 +315,21 @@ bool cpu_is_hotpluggable(unsigned cpu)
}
EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);

+int cpu_set_busy(unsigned int id, int busy)
+{
+ int old;
+ struct device *device = get_cpu_device(id);
+ struct cpu *cpu = container_of(device, struct cpu, dev);
+
+ cpu_hotplug_driver_lock();
+ old = cpu->busy;
+ cpu->busy = busy;
+ cpu_hotplug_driver_unlock();
+
+ return old;
+}
+EXPORT_SYMBOL_GPL(cpu_set_busy);
+
#ifdef CONFIG_GENERIC_CPU_DEVICES
static DEFINE_PER_CPU(struct cpu, cpu_devices);
#endif
diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
index 4dcfced..95bde8a 100644
--- a/drivers/xen/cpu_hotplug.c
+++ b/drivers/xen/cpu_hotplug.c
@@ -9,7 +9,7 @@
static void enable_hotplug_cpu(int cpu)
{
if (!cpu_present(cpu))
- arch_register_cpu(cpu);
+ arch_register_cpu(cpu, 0);

set_cpu_present(cpu, true);
}
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index ce7a074..557501b 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -23,12 +23,14 @@ struct device;
struct cpu {
int node_id; /* The node which contains the CPU */
int hotpluggable; /* creates sysfs control file if hotpluggable */
+ int busy;
struct device dev;
};

extern int register_cpu(struct cpu *cpu, int num);
extern struct device *get_cpu_device(unsigned cpu);
extern bool cpu_is_hotpluggable(unsigned cpu);
+extern int cpu_set_busy(unsigned int cpu, int busy);

extern int cpu_add_dev_attr(struct device_attribute *attr);
extern void cpu_remove_dev_attr(struct device_attribute *attr);
--
1.7.9.5


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