Hi guys, i tried cpuhotplug on pandaboard for both Pandroid_Froyo_L27.8.2_release_pkg and Linaro 11.11. It has failed to work stably. On Pandroid_Froyo_L27.8.2_release_pkg, unplugging cpu1 works well: # echo 0 > /sys/devices/system/cpu/cpu1/online CPU1: shutdown
if i enable the cpu1 again by "echo 1 > /sys/devices/system/cpu/cpu1/online", the system will restore to 3 random status: hang, normal, panic.
Using Linaro 11.11 release, "echo 0 > /sys/devices/system/cpu/cpu1/online" will make system hang and the whole system will not be able to reset by pressing reset key, the only way to reset system is pulling out AV power.
i am sorry i can't get more time to debug and find more clues. just want to ask people whether this is a version the cpuhotplug works normal on?
Thanks barry
On Wed, Dec 21, 2011 at 05:23:48PM +0800, Barry Song wrote:
Hi guys, i tried cpuhotplug on pandaboard for both Pandroid_Froyo_L27.8.2_release_pkg and Linaro 11.11. It has failed to work stably. On Pandroid_Froyo_L27.8.2_release_pkg, unplugging cpu1 works well: # echo 0 > /sys/devices/system/cpu/cpu1/online CPU1: shutdown
if i enable the cpu1 again by "echo 1 > /sys/devices/system/cpu/cpu1/online", the system will restore to 3 random status: hang, normal, panic.
Using Linaro 11.11 release, "echo 0 > /sys/devices/system/cpu/cpu1/online" will make system hang and the whole system will not be able to reset by pressing reset key, the only way to reset system is pulling out AV power.
i am sorry i can't get more time to debug and find more clues. just want to ask people whether this is a version the cpuhotplug works normal on?
cpu hotplug is basically totally buggered - the preconditions placed upon the bringup code path are basically impossible to satisfy in any shape or form at the moment.
There's the requirement that the secondary CPU is marked online and active before interrupts are enabled for the thread migration stuff to behave correctly. However, this is incompatible with smp_call_function() which will wait for online CPUs to respond to an IPI - which this one won't because interrupts are disabled.
I think there was some discussion about how to fix this but I don't recall the details.
2011/12/21 Russell King - ARM Linux linux@arm.linux.org.uk:
On Wed, Dec 21, 2011 at 05:23:48PM +0800, Barry Song wrote:
Hi guys, i tried cpuhotplug on pandaboard for both Pandroid_Froyo_L27.8.2_release_pkg and Linaro 11.11. It has failed to work stably. On Pandroid_Froyo_L27.8.2_release_pkg, unplugging cpu1 works well: # echo 0 > /sys/devices/system/cpu/cpu1/online CPU1: shutdown
if i enable the cpu1 again by "echo 1 > /sys/devices/system/cpu/cpu1/online", the system will restore to 3 random status: hang, normal, panic.
Using Linaro 11.11 release, "echo 0 > /sys/devices/system/cpu/cpu1/online" will make system hang and the whole system will not be able to reset by pressing reset key, the only way to reset system is pulling out AV power.
i am sorry i can't get more time to debug and find more clues. just want to ask people whether this is a version the cpuhotplug works normal on?
cpu hotplug is basically totally buggered - the preconditions placed upon the bringup code path are basically impossible to satisfy in any shape or form at the moment.
There's the requirement that the secondary CPU is marked online and active before interrupts are enabled for the thread migration stuff to behave correctly. However, this is incompatible with smp_call_function() which will wait for online CPUs to respond to an IPI - which this one won't because interrupts are disabled.
I think there was some discussion about how to fix this but I don't recall the details.
thanks, Russell. then could i think this is an ARM-kernel-specific bug which exists on all ARM SMP chips for the moment? and that bug doesn't happen on x86: root@ubuntu:~/simple-rootfs/initrd/bin# echo 0 > /sys/devices/system/cpu/cpu3/online root@ubuntu:~/simple-rootfs/initrd/bin# echo 1 > /sys/devices/system/cpu/cpu3/online root@ubuntu:~/simple-rootfs/initrd/bin# echo 0 > /sys/devices/system/cpu/cpu2/online root@ubuntu:~/simple-rootfs/initrd/bin# echo 1 > /sys/devices/system/cpu/cpu2/online
-barry
On Wed, Dec 21, 2011 at 05:59:07PM +0800, Barry Song wrote:
2011/12/21 Russell King - ARM Linux linux@arm.linux.org.uk:
cpu hotplug is basically totally buggered - the preconditions placed upon the bringup code path are basically impossible to satisfy in any shape or form at the moment.
There's the requirement that the secondary CPU is marked online and active before interrupts are enabled for the thread migration stuff to behave correctly. However, this is incompatible with smp_call_function() which will wait for online CPUs to respond to an IPI - which this one won't because interrupts are disabled.
I think there was some discussion about how to fix this but I don't recall the details.
thanks, Russell. then could i think this is an ARM-kernel-specific bug which exists on all ARM SMP chips for the moment? and that bug doesn't happen on x86:
I don't think so. There's nothing ARM specific about it.
+ Peter Z
On Wed, Dec 21, 2011 at 3:37 PM, Russell King - ARM Linux linux@arm.linux.org.uk wrote:
On Wed, Dec 21, 2011 at 05:59:07PM +0800, Barry Song wrote:
2011/12/21 Russell King - ARM Linux linux@arm.linux.org.uk:
cpu hotplug is basically totally buggered - the preconditions placed upon the bringup code path are basically impossible to satisfy in any shape or form at the moment.
There's the requirement that the secondary CPU is marked online and active before interrupts are enabled for the thread migration stuff to behave correctly. However, this is incompatible with smp_call_function() which will wait for online CPUs to respond to an IPI - which this one won't because interrupts are disabled.
I think there was some discussion about how to fix this but I don't recall the details.
thanks, Russell. then could i think this is an ARM-kernel-specific bug which exists on all ARM SMP chips for the moment? and that bug doesn't happen on x86:
I don't think so. There's nothing ARM specific about it.
There are few patches floating around for this issue. I posted one version long back [1] and then there was one more form Thomas G. The most recent is from one is from Peter Z [2] which is moving the fix for the cup online race to core code.
Can you try Peter's patch with your test-case ?
Regards, Santosh
[1] https://lkml.org/lkml/2011/6/20/79 [2] https://lkml.org/lkml/2011/12/15/255
On Thu, Dec 22, 2011 at 02:19:23PM +0530, Shilimkar, Santosh wrote:
- Peter Z
On Wed, Dec 21, 2011 at 3:37 PM, Russell King - ARM Linux linux@arm.linux.org.uk wrote:
On Wed, Dec 21, 2011 at 05:59:07PM +0800, Barry Song wrote:
2011/12/21 Russell King - ARM Linux linux@arm.linux.org.uk:
cpu hotplug is basically totally buggered - the preconditions placed upon the bringup code path are basically impossible to satisfy in any shape or form at the moment.
There's the requirement that the secondary CPU is marked online and active before interrupts are enabled for the thread migration stuff to behave correctly. However, this is incompatible with smp_call_function() which will wait for online CPUs to respond to an IPI - which this one won't because interrupts are disabled.
I think there was some discussion about how to fix this but I don't recall the details.
thanks, Russell. then could i think this is an ARM-kernel-specific bug which exists on all ARM SMP chips for the moment? and that bug doesn't happen on x86:
I don't think so. There's nothing ARM specific about it.
There are few patches floating around for this issue. I posted one version long back [1] and then there was one more form Thomas G. The most recent is from one is from Peter Z [2] which is moving the fix for the cup online race to core code.
Can you try Peter's patch with your test-case ?
Regards, Santosh
[1] https://lkml.org/lkml/2011/6/20/79 [2] https://lkml.org/lkml/2011/12/15/255
[1] is already fixed - and is not the latest "problem" with this code. Fixing the problem in [1] actually itself created the latest problem with smp_call_function() which wasn't there before this change. Patch [2] refers to this problem and proposes a fix for it.
On Thu, Dec 22, 2011 at 3:54 PM, Russell King - ARM Linux linux@arm.linux.org.uk wrote:
On Thu, Dec 22, 2011 at 02:19:23PM +0530, Shilimkar, Santosh wrote:
- Peter Z
On Wed, Dec 21, 2011 at 3:37 PM, Russell King - ARM Linux linux@arm.linux.org.uk wrote:
On Wed, Dec 21, 2011 at 05:59:07PM +0800, Barry Song wrote:
2011/12/21 Russell King - ARM Linux linux@arm.linux.org.uk:
cpu hotplug is basically totally buggered - the preconditions placed upon the bringup code path are basically impossible to satisfy in any shape or form at the moment.
There's the requirement that the secondary CPU is marked online and active before interrupts are enabled for the thread migration stuff to behave correctly. However, this is incompatible with smp_call_function() which will wait for online CPUs to respond to an IPI - which this one won't because interrupts are disabled.
I think there was some discussion about how to fix this but I don't recall the details.
thanks, Russell. then could i think this is an ARM-kernel-specific bug which exists on all ARM SMP chips for the moment? and that bug doesn't happen on x86:
I don't think so. There's nothing ARM specific about it.
There are few patches floating around for this issue. I posted one version long back [1] and then there was one more form Thomas G. The most recent is from one is from Peter Z [2] which is moving the fix for the cup online race to core code.
Can you try Peter's patch with your test-case ?
Regards, Santosh
[1] https://lkml.org/lkml/2011/6/20/79 [2] https://lkml.org/lkml/2011/12/15/255
[1] is already fixed - and is not the latest "problem" with this code. Fixing the problem in [1] actually itself created the latest problem with smp_call_function() which wasn't there before this change. Patch [2] refers to this problem and proposes a fix for it.
Thanks Russell for information. Looks like I missed in between thread.
Regards Santosh
-
Barry Song -
Russell King - ARM Linux -
Shilimkar, Santosh