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([2601:646:c200:7429:e00c:94b8:58e8:8ffb]) by smtp.gmail.com with ESMTPSA id v19-v6sm15420019pgn.94.2018.09.15.12.58.22 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 15 Sep 2018 12:58:22 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (1.0) Subject: Re: [PATCH net-next v3 01/17] asm: simd context helper API From: Andy Lutomirski X-Mailer: iPhone Mail (15G77) In-Reply-To: Date: Sat, 15 Sep 2018 12:58:21 -0700 Cc: kevin@guarana.org, Andrew Lutomirski , LKML , Netdev , David Miller , Greg Kroah-Hartman , Thomas Gleixner , Samuel Neves , linux-arch@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <61B4DFD6-9BB5-4B81-BD0E-ACF112EA8AF7@amacapital.net> References: <20180911010838.8818-1-Jason@zx2c4.com> <20180911010838.8818-2-Jason@zx2c4.com> <20180912061433.GA8484@ip-172-31-15-78> <20180913050301.GA26367@ip-172-31-15-78> To: "Jason A. Donenfeld" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Sep 13, 2018, at 6:52 AM, Jason A. Donenfeld wrote: >=20 >> On Thu, Sep 13, 2018 at 7:03 AM Kevin Easton wrote: >> Yes. It's also how most get/put APIs already work in the kernel, eg >> kref_get/put (mostly because they tend to be 'getting/putting' an >> already-initialized object, though). >=20 > Right; in this case the object wouldn't be initialized yet, which > might defeat the purpose, since one advantage of the & way you > mentioned is _put modifies the context. >=20 > Andy - any opinions on this? The tl;dr is: >=20 > 1) what we have now: >=20 > simd_context_t simd_context =3D simd_get(); > for (item in items) { > do_something(item); > simd_context =3D simd_relax(simd_context); > } > simd_put(); >=20 > 2) what kevin is proposing: >=20 > simd_context_t simd_context; >=20 > simd_get(&simd_context); > for (item in items) { > do_something(item); > simd_relax(&simd_context); > } > simd_put(&simd_context); >=20 > I can see pros and cons of each approach. I have no strong opinion, except that, if you paint the bikeshed =E2=80=9Cpa= ss by value=E2=80=9D, then simd_get and simd_relax should probably have warn= _unused_result set.=