linux-kernel - [PATCH -tip v1 0/3] seqlock: assorted cleanups

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Date:   Sun,  6 Dec 2020 17:21:40 +0100
From:   "Ahmed S. Darwish" <a.darwish@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Jonathan Corbet <corbet@....net>,
        Jason Gunthorpe <jgg@...dia.com>,
        John Hubbard <jhubbard@...dia.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "Sebastian A. Siewior" <bigeasy@...utronix.de>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>
Subject: [PATCH -tip v1 0/3] seqlock: assorted cleanups

Hi,

When the seqcount_LOCKNAME_t group of data types were introduced, two
classes of seqlock.h sequence counter macros were added:

  - An external public API which can either take a plain seqcount_t or
    any of the seqcount_LOCKNAME_t variants.

  - An internal API which takes only a plain seqcount_t.

To distinguish between the two groups, the "*_seqcount_t_*" pattern was
used for the latter. This confused a number of mm/ call-site developers,
and Linus also commented that this was not the standard practice for
marking kernel internal APIs. [1]

Distinguish the latter group of macros by prefixing a "do_".

A number of call-site developers also complained that the automatic
preemption disable/enable for the write side macros was not obvious, or
documented. [2] Linus also suggested adding few comments explaining that
behavior. [3] Fix it by completing the seqcount write side kernel-doc
annotations.

Finally, fix a minor naming inconsistency w.r.t. seqlock.h
vs. Documentation/locking/seqlock.rst.

This series does not change the output "allyesconfig" kernel binary:

    text         data            bss      ...        filename
  247616963    289662125       81498728   ...  ../build-x86-64/vmlinux.old
  247616963    289662125       81498728   ...  ../build-x86-64/vmlinux
  145054028    78270273        18435468   ...  ../build-arm/vmlinux.old
  145054028    78270273        18435468   ...  ../build-arm/vmlinux

Note: based over -tip locking/core, instead of latest -rc, due to -tip
      ab440b2c604b ("seqlock: Rename __seqprop() users").

References:

[1] https://lkml.kernel.org/r/CAHk-=wgB8nyOQufpn0o6a5BpJCJPnXvH+kRxApujhsgG+7qAwQ@mail.gmail.com
[2] https://lkml.kernel.org/r/20201030235121.GQ2620339@nvidia.com
[3] https://lkml.kernel.org/r/CAHk-=wikhGExmprXgaW+MVXG1zsGpztBbVwOb23vetk41EtTBQ@mail.gmail.com

8<--------------

Ahmed S. Darwish (3):
  Documentation: seqlock: s/LOCKTYPE/LOCKNAME/g
  seqlock: Prefix internal seqcount_t-only macros with a "do_"
  seqlock: kernel-doc: Specify when preemption is automatically altered

 Documentation/locking/seqlock.rst | 21 ++++----
 include/linux/seqlock.h           | 83 ++++++++++++++++---------------
 2 files changed, 54 insertions(+), 50 deletions(-)

base-commit: 97d62caa32d6d79dadae3f8d19af5c92ea9a589a
--
2.29.2