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possible_cpus broken in linux-next

DISCUSSION Applied Dave Hansen 5 participants 6 messages May 29, 2013

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ACPI Driver core
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Dave Hansen

author
#0 lore raw

If I boot with: maxcpus=2 possible_cpus=4, I get

	# grep . /sys/devices/system/cpu/cpu[0-9]*/online'
	/sys/devices/system/cpu/cpu1/online:1
	/sys/devices/system/cpu/cpu2/online:1
	/sys/devices/system/cpu/cpu3/online:1

on bad kernels, and this on working ones:

/sys/devices/system/cpu/cpu1/online:1
/sys/devices/system/cpu/cpu2/online:0
/sys/devices/system/cpu/cpu3/online:0

I also get -EINVAL if I try to re-offline them in this state. 2 and 3 don't show up in /proc/cpuinfo, so sysfs just looks broken here. This happens in a KVM guest, so it should be dirt-simple for anyone to reproduce.

I bisected it down to:

Quoted 22 lines

commit 0902a9044fa5b7a0456ea4daacec2c2b3189ba8c

Author: Rafael J. Wysocki <[email protected]>
Date:   Fri May 3 00:25:49 2013 +0200

Driver core: Use generic offline/online for CPU offline/online

Rework the CPU hotplug code in drivers/base/cpu.c to use the generic offline/online support introduced previously instead of its own CPU-specific code.

For this purpose, modify cpu_subsys to provide offline and online callbacks for CONFIG_HOTPLUG_CPU set and remove the code handling the CPU-specific 'online' sysfs attribute.

This modification is not supposed to change the user-observable behavior of the kernel (i.e. the 'online' attribute will be present in exactly the same place in sysfs and should trigger exactly the same actions as before).

Signed-off-by Rafael J. Wysocki <[email protected]>
Acked-by Greg Kroah-Hartman <[email protected]>
Reviewed-by Toshi Kani <[email protected]>
#1 lore raw
Quoted 14 lines · Dave Hansen

If I boot with: maxcpus=2 possible_cpus=4, I get

	# grep . /sys/devices/system/cpu/cpu[0-9]*/online'
	/sys/devices/system/cpu/cpu1/online:1
	/sys/devices/system/cpu/cpu2/online:1
	/sys/devices/system/cpu/cpu3/online:1

on bad kernels, and this on working ones:

/sys/devices/system/cpu/cpu1/online:1
/sys/devices/system/cpu/cpu2/online:0
/sys/devices/system/cpu/cpu3/online:0

Quoted 28 lines

I also get -EINVAL if I try to re-offline them in this state. 2 and 3 don't show up in /proc/cpuinfo, so sysfs just looks broken here. This happens in a KVM guest, so it should be dirt-simple for anyone to reproduce.

I bisected it down to:

Quoted 22 lines

commit 0902a9044fa5b7a0456ea4daacec2c2b3189ba8c

Author: Rafael J. Wysocki <[email protected]>
Date:   Fri May 3 00:25:49 2013 +0200

Driver core: Use generic offline/online for CPU offline/online

Rework the CPU hotplug code in drivers/base/cpu.c to use the generic offline/online support introduced previously instead of its own CPU-specific code.

For this purpose, modify cpu_subsys to provide offline and online callbacks for CONFIG_HOTPLUG_CPU set and remove the code handling the CPU-specific 'online' sysfs attribute.

This modification is not supposed to change the user-observable behavior of the kernel (i.e. the 'online' attribute will be present in exactly the same place in sysfs and should trigger exactly the same actions as before).

Signed-off-by Rafael J. Wysocki <[email protected]>
Acked-by Greg Kroah-Hartman <[email protected]>
Reviewed-by Toshi Kani <[email protected]>

Thanks for the report. The following patch fixes the problem. -Toshi

====
From: Toshi Kani <[email protected]>
Subject: [PATCH] ACPI: Fix sysfs cpu/online of offlined cpus

As reported by Dave Hansen, sysfs cpu/online shows 1 for offlined cpus at boot.
https://lkml.org/lkml/2013/5/29/403

Fix this problem by initializing dev.offline with cpu_online() when registering a cpu.

Reported-by Dave Hansen <[email protected]>
Signed-off-by Toshi Kani <[email protected]>
---
 drivers/base/cpu.c | 1 +
 1 file changed, 1 insertion(+)
drivers/base/cpu.c +1 -0
index 130ba0b..b9f0eec 100644
@@ -281,6 +281,7 @@ int __cpuinit register_cpu(struct cpu *cpu, int num)
 	cpu->dev.bus = &cpu_subsys;
 	cpu->dev.release = cpu_device_release;
 	cpu->dev.offline_disabled = !cpu->hotpluggable;
+	cpu->dev.offline = !cpu_online(num);
 #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
 	cpu->dev.bus->uevent = arch_cpu_uevent;
 #endif
Signature · 1 line
1.8.1.4
#2 lore raw
Quoted 1 line · Toshi Kani

On Wed, 2013-05-29 at 10:10 -0700, Dave Hansen wrote:

:

Quoted 6 lines

Thanks for the report. The following patch fixes the problem. -Toshi

====
From: Toshi Kani <[email protected]>
Subject: [PATCH] ACPI: Fix sysfs cpu/online of offlined cpus

Typo. The subject needs to be:

Subject: [PATCH] cpu: Fix sysfs cpu/online of offlined cpus

-Toshi

Quoted 25 lines

As reported by Dave Hansen, sysfs cpu/online shows 1 for offlined cpus at boot.
https://lkml.org/lkml/2013/5/29/403

Fix this problem by initializing dev.offline with cpu_online() when registering a cpu.

Reported-by Dave Hansen <[email protected]>
Signed-off-by Toshi Kani <[email protected]>
---
 drivers/base/cpu.c | 1 +
 1 file changed, 1 insertion(+)
drivers/base/cpu.c +1 -0
index 130ba0b..b9f0eec 100644
@@ -281,6 +281,7 @@ int __cpuinit register_cpu(struct cpu *cpu, int num)
 	cpu->dev.bus = &cpu_subsys;
 	cpu->dev.release = cpu_device_release;
 	cpu->dev.offline_disabled = !cpu->hotpluggable;
+	cpu->dev.offline = !cpu_online(num);
 #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
 	cpu->dev.bus->uevent = arch_cpu_uevent;
 #endif
#3 lore raw
Quoted 7 lines · Toshi Kani
Quoted 1 line · Toshi Kani

On Wed, 2013-05-29 at 10:10 -0700, Dave Hansen wrote:

:

Quoted 3 lines

Thanks for the report. The following patch fixes the problem. -Toshi

Quoted 18 lines
Quoted 3 lines

====
From: Toshi Kani <[email protected]>
Subject: [PATCH] ACPI: Fix sysfs cpu/online of offlined cpus

Typo. The subject needs to be:

Subject: [PATCH] cpu: Fix sysfs cpu/online of offlined cpus

-Toshi

Quoted 9 lines

As reported by Dave Hansen, sysfs cpu/online shows 1 for offlined cpus at boot.
https://lkml.org/lkml/2013/5/29/403

Fix this problem by initializing dev.offline with cpu_online() when registering a cpu.

Reported-by Dave Hansen <[email protected]>
Signed-off-by Toshi Kani <[email protected]>

Thanks Toshi!

Dave, can you please confirm that the problem is fixed by this patch?

Rafael

Quoted 4 lines
Quoted 4 lines
---
  drivers/base/cpu.c | 1 +
  1 file changed, 1 insertion(+)
Quoted 13 lines

drivers/base/cpu.c int __cpuinit register_cpu(struct cpu *cpu, int num) · line 287

Quoted 12 lines
drivers/base/cpu.c +1 -0
index 130ba0b..b9f0eec 100644
@@ -281,6 +281,7 @@ int __cpuinit register_cpu(struct cpu *cpu, int num)
  	cpu->dev.bus = &cpu_subsys;
  	cpu->dev.release = cpu_device_release;
  	cpu->dev.offline_disabled = !cpu->hotpluggable;
+	cpu->dev.offline = !cpu_online(num);
  #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
  	cpu->dev.bus->uevent = arch_cpu_uevent;
  #endif

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Tested-by
#4 lore raw
Quoted 4 lines · Rafael J. Wysocki
Quoted 4 lines
Quoted 4 lines
drivers/base/cpu.c +0 -0
index 130ba0b..b9f0eec 100644
Quoted 8 lines
Quoted 8 lines

drivers/base/cpu.c int __cpuinit register_cpu(struct cpu *cpu, int num) · line 287

Quoted 8 lines
drivers/base/cpu.c +1 -0
@@ -281,6 +281,7 @@ int __cpuinit register_cpu(struct cpu *cpu, int num)
      cpu->dev.bus = &cpu_subsys;
      cpu->dev.release = cpu_device_release;
      cpu->dev.offline_disabled = !cpu->hotpluggable;
+    cpu->dev.offline = !cpu_online(num);
  #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
      cpu->dev.bus->uevent = arch_cpu_uevent;
  #endif

This gets things working for me again. Thanks for the quick response!

Tested-by Dave Hansen <[email protected]>
Applied
#5 lore raw
Quoted 16 lines · Dave Hansen
Quoted 4 lines · Rafael J. Wysocki
Quoted 4 lines
Quoted 4 lines
drivers/base/cpu.c +0 -0
index 130ba0b..b9f0eec 100644
Quoted 8 lines
Quoted 8 lines

drivers/base/cpu.c int __cpuinit register_cpu(struct cpu *cpu, int num) · line 287

Quoted 8 lines
drivers/base/cpu.c +1 -0
@@ -281,6 +281,7 @@ int __cpuinit register_cpu(struct cpu *cpu, int num)
      cpu->dev.bus = &cpu_subsys;
      cpu->dev.release = cpu_device_release;
      cpu->dev.offline_disabled = !cpu->hotpluggable;
+    cpu->dev.offline = !cpu_online(num);
  #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
      cpu->dev.bus->uevent = arch_cpu_uevent;
  #endif

This gets things working for me again. Thanks for the quick response!

Quoted 1 line
Tested-by Dave Hansen <[email protected]>

Applied.

Thanks,
Rafael

Signature · 2 lines
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.