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From:   Andy Lutomirski <luto@amacapital.net>
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Subject: Re: [RESEND][PATCH v3 14/17] static_call: Add static_cond_call()
Date:   Tue, 24 Mar 2020 09:22:29 -0700
Message-Id: <86D80EA7-9087-4042-8119-12DD5FCEAA87@amacapital.net>
References: <CAHk-=wiumU4QxAkT+GqhBt5f-iUsoLNC0sqVfRKp0xypA6aNYg@mail.gmail.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Jason Baron <jbaron@akamai.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>, Nadav Amit <namit@vmware.com>,
        Peter Anvin <hpa@zytor.com>,
        Andrew Lutomirski <luto@kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>
In-Reply-To: <CAHk-=wiumU4QxAkT+GqhBt5f-iUsoLNC0sqVfRKp0xypA6aNYg@mail.gmail.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Sender: linux-kernel-owner@vger.kernel.org
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> On Mar 24, 2020, at 9:14 AM, Linus Torvalds <torvalds@linux-foundation.org=
> wrote:
>=20
> =EF=BB=BFOn Tue, Mar 24, 2020 at 7:25 AM Peter Zijlstra <peterz@infradead.=
org> wrote:
>>=20
>> Extend the static_call infrastructure to optimize the following common
>> pattern:
>>=20
>>        if (func_ptr)
>>                func_ptr(args...)
>=20
> Is there any reason why this shouldn't be the default static call pattern?=

>=20
> IOW, do we need the special "cond" versions at all? Couldn't we just
> say that this is how static calls fundamentally work - if the function
> is NULL, they are nops?
>=20
>=20

I haven=E2=80=99t checked if static calls currently support return values, b=
ut the conditional case only makes sense for functions that return void.=20

Aside from that, it might be nice for passing NULL in to warn or bug when th=
e NULL pointer is stored instead of silently NOPping out the call in cases w=
here having a real implementation isn=E2=80=99t optional.=