Re: [PATCH v2 1/1] percpu-refcount: do not forget to rcu_barrier() just before freeing

From	Roman Penyaev <roman.penyaev@profitbricks.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 1/1] percpu-refcount: do not forget to rcu_barrier() just before freeing
Date	2016-08-11 19:40 +0200
Message-ID	<s527v-6Tl-9@gated-at.bofh.it> (permalink)
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Hi,

On Thu, Aug 11, 2016 at 6:29 PM, Tejun Heo <tj@kernel.org> wrote:
> Hello, Roman.
>
> On Thu, Aug 11, 2016 at 11:07:14AM +0200, Roman Penyaev wrote:
>> Yes, exactly, this is an illegal operation.  But it is not more illegal
>> than calling kill() twice or reinit() when counter is not yet zero.
>> And those illegals are covered with warnings, which can be observed
>> for example with this freeze/unfreeze blk-mq bug.
>
> I have no objections about adding warnings for these conditions;
> however, adding rcu barrier to mask illegal usages is a very different
> thing.  That adds a lot of unnecessary latency to the exit function
> and makes it unusable from non-sleepable contexts.
>

Yes, for sure that makes sense.  I changed the patch a little.
Have sent.

--
Roman

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Re: [PATCH v2 1/1] percpu-refcount: do not forget to rcu_barrier()  just before freeing Tejun Heo <tj@kernel.org> - 2016-08-11 00:10 +0200
  Re: [PATCH v2 1/1] percpu-refcount: do not forget to rcu_barrier()  just before freeing Roman Penyaev <roman.penyaev@profitbricks.com> - 2016-08-11 11:10 +0200
    Re: [PATCH v2 1/1] percpu-refcount: do not forget to rcu_barrier()  just before freeing Tejun Heo <tj@kernel.org> - 2016-08-11 18:30 +0200
      Re: [PATCH v2 1/1] percpu-refcount: do not forget to rcu_barrier()  just before freeing Roman Penyaev <roman.penyaev@profitbricks.com> - 2016-08-11 19:40 +0200

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