Re: [PATCH 2/3] percpu counter: cast this_cpu_sub() adjustment

From: Greg Thelen
Date: Sun Oct 27 2013 - 12:13:33 EST

On Sun, Oct 27 2013, Tejun Heo wrote:

> On Sun, Oct 27, 2013 at 05:04:29AM -0700, Andrew Morton wrote:
>> On Sun, 27 Oct 2013 07:22:55 -0400 Tejun Heo <tj@xxxxxxxxxx> wrote:
>> > We probably want to cc stable for this and the next one. How should
>> > these be routed? I can take these through percpu tree or mm works
>> > too. Either way, it'd be best to route them together.
>> Yes, all three look like -stable material to me. I'll grab them later
>> in the week if you haven't ;)
> Tried to apply to percpu but the third one is a fix for a patch which
> was added to -mm during v3.12-rc1, so these are yours. :)

I don't object to stable for the first two non-memcg patches, but it's
probably unnecessary. I should have made it more clear, but an audit of
v3.12-rc6 shows that only new memcg code is affected - the new
mem_cgroup_move_account_page_stat() is the only place where an unsigned
adjustment is used. All other callers (e.g. shrink_dcache_sb) already
use a signed adjustment, so no problems before v3.12. Though I did not
audit the stable kernel trees, so there could be something hiding in

>> The names of the first two patches distress me. They rather clearly
>> assert that the code affects percpu_counter.[ch], but that is not the case.
>> Massaging is needed to fix that up.
> Yeah, something like the following would be better
> percpu: add test module for various percpu operations
> percpu: fix this_cpu_sub() subtrahend casting for unsigneds
> memcg: use __this_cpu_sub() to dec stats to avoid incorrect subtrahend casting

No objection to renaming. Let me know if you want these reposed with
updated titles.
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