Commit 12633e80 authored by Nathan Fontenot's avatar Nathan Fontenot Committed by Benjamin Herrenschmidt
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sysfs/cpu: Add probe/release files

Version 3 of this patch is updated with documentation added to
Documentation/ABI.  There are no changes to any of the C code from v2
of the patch.

In order to support kernel DLPAR of CPU resources we need to provide an
interface to add (probe) and remove (release) the resource from the system.
This patch Creates new generic probe and release sysfs files to facilitate
cpu probe/release.  The probe/release interface provides for allowing each
arch to supply their own routines for implementing the backend of adding
and removing cpus to/from the system.

This also creates the powerpc specific stubs to handle the arch callouts
from writes to the sysfs files.

The creation and use of these files is regulated by the
CONFIG_ARCH_CPU_PROBE_RELEASE option so that only architectures that need the
capability will have the files created.
Signed-off-by: default avatarNathan Fontenot <>
Signed-off-by: default avatarBenjamin Herrenschmidt <>
parent ab519a01
......@@ -62,6 +62,21 @@ Description: CPU topology files that describe kernel limits related to
See Documentation/cputopology.txt for more information.
What: /sys/devices/system/cpu/probe
Date: November 2009
Contact: Linux kernel mailing list <>
Description: Dynamic addition and removal of CPU's. This is not hotplug
removal, this is meant complete removal/addition of the CPU
from the system.
probe: writes to this file will dynamically add a CPU to the
system. Information written to the file to add CPU's is
architecture specific.
release: writes to this file dynamically remove a CPU from
the system. Information writtento the file to remove CPU's
is architecture specific.
What: /sys/devices/system/cpu/cpu#/node
Date: October 2009
......@@ -320,6 +320,10 @@ config HOTPLUG_CPU
Say N if you are unsure.
def_bool y
depends on HOTPLUG_CPU
def_bool y
......@@ -266,6 +266,11 @@ struct machdep_calls {
void (*suspend_disable_irqs)(void);
void (*suspend_enable_irqs)(void);
ssize_t (*cpu_probe)(const char *, size_t);
ssize_t (*cpu_release)(const char *, size_t);
extern void e500_idle(void);
......@@ -461,6 +461,25 @@ static void unregister_cpu_online(unsigned int cpu)
ssize_t arch_cpu_probe(const char *buf, size_t count)
if (ppc_md.cpu_probe)
return ppc_md.cpu_probe(buf, count);
return -EINVAL;
ssize_t arch_cpu_release(const char *buf, size_t count)
if (ppc_md.cpu_release)
return ppc_md.cpu_release(buf, count);
return -EINVAL;
static int __cpuinit sysfs_cpu_notify(struct notifier_block *self,
......@@ -72,6 +72,38 @@ void unregister_cpu(struct cpu *cpu)
per_cpu(cpu_sys_devices, logical_cpu) = NULL;
static ssize_t cpu_probe_store(struct class *class, const char *buf,
size_t count)
return arch_cpu_probe(buf, count);
static ssize_t cpu_release_store(struct class *class, const char *buf,
size_t count)
return arch_cpu_release(buf, count);
static CLASS_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
static CLASS_ATTR(release, S_IWUSR, NULL, cpu_release_store);
int __init cpu_probe_release_init(void)
int rc;
rc = sysfs_create_file(&cpu_sysdev_class.kset.kobj,
if (!rc)
rc = sysfs_create_file(&cpu_sysdev_class.kset.kobj,
return rc;
#else /* ... !CONFIG_HOTPLUG_CPU */
static inline void register_cpu_control(struct cpu *cpu)
......@@ -43,6 +43,8 @@ extern int sched_create_sysfs_power_savings_entries(struct sysdev_class *cls);
extern void unregister_cpu(struct cpu *cpu);
extern ssize_t arch_cpu_probe(const char *, size_t);
extern ssize_t arch_cpu_release(const char *, size_t);
struct notifier_block;
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