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cpu: make sure that cpu/online file created before KOBJ_ADD is emitted
It fixes race between udev and hotplugged CPU registration by defining "online" attribute statically, so that device_add() would create it before notifying udev about new CPU. Original issue report is at https://lkml.org/lkml/2012/4/30/198 " > On Mon, Apr 30, 2012 at 11:36:23AM -0400, Konrad Rzeszutek Wilk wrote: > > Hey Greg, > > > > Hoping you can help with some guidance on how to fix this. > > > > The issue is with CPU hotplug is that when a CPU goes up > > it calls 'arch_register_cpu' which eventually calls > > register_cpu. That function does these two things: > > > > 251 error = device_register(&cpu->dev); > > 252 if (!error && cpu->hotpluggable) > > 253 register_cpu_control(cpu); > > > > and the device_register creates a nice little SysFS directory: > > > > /sys/devices/system/cpu/cpu2/ which at line 251 has the 'add' attribute > > but no 'online' attribute. udev then tries to echo 1 to the 'online' > > and it we get: > > udevd-work[2421]: error opening ATTR{/sys/devices/system/cpu/cpu2/online} for writing: No such file or directory > > > > Line 253 creates said 'online' and at that time udev [or the system admin] > > can write 1 to 'online' and the CPU goes up. > > > > So .. any thoughts? Is there some way to inhibit from uevent being sent > > until line 253 has run? " Signed-off-by: Igor Mammedov <imammedo@redhat.com> Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -85,18 +85,21 @@ static ssize_t __ref store_online(struct device *dev,
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}
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static DEVICE_ATTR(online, 0644, show_online, store_online);
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static void __cpuinit register_cpu_control(struct cpu *cpu)
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{
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device_create_file(&cpu->dev, &dev_attr_online);
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}
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static struct attribute *hotplug_cpu_attrs[] = {
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&dev_attr_online.attr,
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NULL
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};
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static struct attribute_group hotplug_cpu_attr_group = {
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.attrs = hotplug_cpu_attrs,
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};
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void unregister_cpu(struct cpu *cpu)
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{
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int logical_cpu = cpu->dev.id;
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unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));
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device_remove_file(&cpu->dev, &dev_attr_online);
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device_unregister(&cpu->dev);
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per_cpu(cpu_sys_devices, logical_cpu) = NULL;
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return;
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@ -122,11 +125,6 @@ static ssize_t cpu_release_store(struct device *dev,
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static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
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static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
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#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
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#else /* ... !CONFIG_HOTPLUG_CPU */
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static inline void register_cpu_control(struct cpu *cpu)
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{
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}
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#endif /* CONFIG_HOTPLUG_CPU */
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#ifdef CONFIG_KEXEC
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@ -183,6 +181,16 @@ static const struct attribute_group *common_cpu_attr_groups[] = {
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NULL
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};
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static const struct attribute_group *hotplugable_cpu_attr_groups[] = {
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#ifdef CONFIG_KEXEC
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&crash_note_cpu_attr_group,
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#endif
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#ifdef CONFIG_HOTPLUG_CPU
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&hotplug_cpu_attr_group,
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#endif
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NULL
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};
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/*
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* Print cpu online, possible, present, and system maps
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*/
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@ -298,9 +306,9 @@ int __cpuinit register_cpu(struct cpu *cpu, int num)
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cpu->dev.bus->uevent = arch_cpu_uevent;
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#endif
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cpu->dev.groups = common_cpu_attr_groups;
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if (cpu->hotpluggable)
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cpu->dev.groups = hotplugable_cpu_attr_groups;
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error = device_register(&cpu->dev);
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if (!error && cpu->hotpluggable)
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register_cpu_control(cpu);
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if (!error)
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per_cpu(cpu_sys_devices, num) = &cpu->dev;
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if (!error)
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