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FS#43088 - [linux] 4.2.x enable CONFIG_CHECKPOINT_RESTORE

Attached to Project: Arch Linux
Opened by Ruslan Kuprieiev (efiop) - Friday, 12 December 2014, 10:54 GMT
Last edited by Tobias Powalowski (tpowa) - Thursday, 03 September 2015, 13:55 GMT
Task Type Feature Request
Category Kernel
Status Closed
Assigned To Tobias Powalowski (tpowa)
Thomas Bächler (brain0)
Architecture x86_64
Severity Low
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 14
Private No


criu project heavily depends on CONFIG_CHECKPOINT_RESTORE, which is disabled in arch since v3.14(
It is enabled by default in all popular linux distros(Debian, Fedora, Ubuntu, etc), so, I guess, it is stable enough.

Additional info:
* package version(s)
* config and/or log files etc.

Steps to reproduce:
This task depends upon

Closed by  Tobias Powalowski (tpowa)
Thursday, 03 September 2015, 13:55 GMT
Reason for closing:  Fixed
Additional comments about closing:  4.2.0-1
Comment by Jan de Groot (JGC) - Friday, 12 December 2014, 12:25 GMT
This was already discussed on arch-dev-public, so far it doesn't look like we will implement this in our stock kernel. The fact that other distributions are enabling an option behind CONFIG_EXPERT doesn't mean we should also do this.
Comment by Daniel Micay (thestinger) - Tuesday, 16 December 2014, 01:42 GMT
Respecting the upstream decision to keep this behind CONFIG_EXPERT is in the spirit of the distribution. It wouldn't be behind it if the upstream intention was for distribution kernels to enable it at this point.
Comment by Ruslan Kuprieiev (efiop) - Tuesday, 23 December 2014, 01:44 GMT
Well, arch has CONFIG_NAMESPACES enabled, even though it is under CONFIG_EXPERT.
Comment by Daniel Micay (thestinger) - Tuesday, 23 December 2014, 01:58 GMT
Arch doesn't enable CONFIG_EXPERT at the moment, so that's not true. It may have been under CONFIG_EXPERT at one point but it hasn't been for quite some time.
Comment by Ruslan Kuprieiev (efiop) - Wednesday, 24 December 2014, 12:03 GMT
Well, thats not true. See
menuconfig NAMESPACES
bool "Namespaces support" if EXPERT

Which means, that CONFIG_NAMESPACE depend on CONFIG_EXPERT and it is enabled it default arch kernel.
Comment by Thomas Bächler (brain0) - Wednesday, 24 December 2014, 12:11 GMT
That's wrong. CONFIG_NAMESPACE does not depend on EXPERT. This only means that you can only configure it with EXPERT. If EXPERT is disabled, CONFIG_NAMESPACE is always on:

menuconfig NAMESPACES
bool "Namespaces support" if EXPERT
default !EXPERT
Comment by Ruslan Kuprieiev (efiop) - Wednesday, 24 December 2014, 13:10 GMT
Oh, now I see. You are absolutely right. Sorry for the noise.

So, what are the requirements to enable CONFIG_CHECKPOINT_RESTORE again?
Is it only to make it enabled without CONFIG_EXPERT?
Comment by Daniel Micay (thestinger) - Wednesday, 24 December 2014, 19:16 GMT
Yes, if it's not behind CONFIG_EXPERT then I don't think there's any reason to leave it disabled. As it is, enabling it would expose a bunch of options that are not really supposed to be there. I interpret the dependency on CONFIG_EXPERT as an indication that it's not yet ready, although perhaps it is a legacy wart.
Comment by Iago López Galeiras (iaguis) - Monday, 18 May 2015, 15:02 GMT
Enabling this option is now "strongly recommended" in systemd for the kcmp() syscall:

Also, in rkt we want to get children information through /proc/<pid>/task/<tid>/children which also depends on CONFIG_CHECKPOINT_RESTORE:

These features should probably be independent from CONFIG_CHECKPOINT_RESTORE but for now it would be nice to have this option enabled in Arch.
Comment by Iago López Galeiras (iaguis) - Monday, 01 June 2015, 09:01 GMT
The patch for separating the enabling of /proc/<pid>/task/<tid>/children from CONFIG_CHECKPOINT_RESTORE is now on linux-next[1] so hopefully it will be part of the 4.2 kernel.

Comment by Tobias Powalowski (tpowa) - Thursday, 03 September 2015, 13:55 GMT
CONFIG_PROC_CHILDREN added to 4.2.0-1