[PATCH 2/2] cpu: make sure that cpu/online file created before KOBJ_ADD is emitted

From: Igor Mammedov
Date: Mon May 13 2013 - 18:09:29 EST


Fixes race between udev and hotplugged CPU registration, described at
https://lkml.org/lkml/2012/4/30/198
by defining "online" attribute statically so that device_add() would
create it before notifying udev about new CPU.

Signed-off-by: Igor Mammedov <imammedo@xxxxxxxxxx>
---
drivers/base/cpu.c | 34 +++++++++++++++++++++-------------
1 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 02e4d73..6578030 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -64,18 +64,21 @@ static ssize_t __ref store_online(struct device *dev,
}
static DEVICE_ATTR(online, 0644, show_online, store_online);

-static void __cpuinit register_cpu_control(struct cpu *cpu)
-{
- device_create_file(&cpu->dev, &dev_attr_online);
-}
+static struct attribute *hotplug_cpu_attrs[] = {
+ &dev_attr_online.attr,
+ NULL
+};
+
+static struct attribute_group hotplug_cpu_attr_group = {
+ .attrs = hotplug_cpu_attrs,
+};
+
void unregister_cpu(struct cpu *cpu)
{
int logical_cpu = cpu->dev.id;

unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));

- device_remove_file(&cpu->dev, &dev_attr_online);
-
device_unregister(&cpu->dev);
per_cpu(cpu_sys_devices, logical_cpu) = NULL;
return;
@@ -101,11 +104,6 @@ static ssize_t cpu_release_store(struct device *dev,
static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
-
-#else /* ... !CONFIG_HOTPLUG_CPU */
-static inline void register_cpu_control(struct cpu *cpu)
-{
-}
#endif /* CONFIG_HOTPLUG_CPU */

#ifdef CONFIG_KEXEC
@@ -150,6 +148,16 @@ static const struct attribute_group *common_cpu_attr_groups[] = {
NULL
};

+static const struct attribute_group *hotplugable_cpu_attr_groups[] = {
+#ifdef CONFIG_KEXEC
+ &crash_note_cpu_attr_group,
+#endif
+#ifdef CONFIG_HOTPLUG_CPU
+ &hotplug_cpu_attr_group,
+#endif
+ NULL
+};
+
/*
* Print cpu online, possible, present, and system maps
*/
@@ -265,9 +273,9 @@ int __cpuinit register_cpu(struct cpu *cpu, int num)
cpu->dev.bus->uevent = arch_cpu_uevent;
#endif
cpu->dev.groups = common_cpu_attr_groups;
+ if (cpu->hotpluggable)
+ cpu->dev.groups = hotplugable_cpu_attr_groups;
error = device_register(&cpu->dev);
- if (!error && cpu->hotpluggable)
- register_cpu_control(cpu);
if (!error)
per_cpu(cpu_sys_devices, num) = &cpu->dev;
if (!error)
--
1.7.1

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