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Re: [PATCH v2] jump_label: reduce the size of struct static_key

From Ingo Molnar <mingo@kernel.org>
Newsgroups linux.kernel
Subject Re: [PATCH v2] jump_label: reduce the size of struct static_key
Date 2017-01-21 08:10 +0100
Message-ID <t1XYd-17D-1@gated-at.bofh.it> (permalink)
References <sVYNk-8qL-7@gated-at.bofh.it> <t1BO1-4ji-1@gated-at.bofh.it> <t1NFv-3kN-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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* Jason Baron <jbaron@akamai.com> wrote:

> >For example the last line could sure be written as:
> >
> >			key->entries = jlm->entries;
> >			key->type |= static_key_type(key);
> >
> >right?
> 
> Hi,
> 
> So that is going to over-write the static_key_type(key) in the first
> assignment. If the order is reversed we can't just |= in the pointer type.

Indeed, I missed that.

> How about:
> 
> static void jump_key_set_entries(struct static_key *key, struct jump_entry *entries)
> {
>        unsigned long type;
> 
>        type = static_key_type(key);
>        key->entries = entries;
>        key->type |= type;
> }
> 
> and then we can also add:
> 
> void jump_key_set_mod(struct static_key *key, struct static_key_mod *mod)
> 
> doing basically the same thing. That will avoid the casts that you called
> out.
> 
> better?

Yeah - and it should generate the exact same code, right?

I'd also add a short comment to the helper function that points out the 
union/aliasing, in case anyone is wondering.

Thanks,

	Ingo

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Thread

Re: [PATCH v2] jump_label: reduce the size of struct static_key Ingo Molnar <mingo@kernel.org> - 2017-01-20 08:30 +0100
  Re: [PATCH v2] jump_label: reduce the size of struct static_key Jason Baron <jbaron@akamai.com> - 2017-01-20 21:10 +0100
    Re: [PATCH v2] jump_label: reduce the size of struct static_key Ingo Molnar <mingo@kernel.org> - 2017-01-21 08:10 +0100
      Re: [PATCH v2] jump_label: reduce the size of struct static_key Jason Baron <jbaron@akamai.com> - 2017-01-23 21:50 +0100

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