linux-kernel - Re: [PATCH v3 00/14] kernel/locking: qspinlock improvements

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Message-ID: <8fdcfa2d-7717-5eb6-a938-53524db8ea41@redhat.com>
Date:   Thu, 26 Apr 2018 16:18:56 -0400
From:   Waiman Long <longman@...hat.com>
To:     Will Deacon <will.deacon@....com>, linux-kernel@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org, peterz@...radead.org,
        mingo@...nel.org, boqun.feng@...il.com, paulmck@...ux.vnet.ibm.com
Subject: Re: [PATCH v3 00/14] kernel/locking: qspinlock improvements

On 04/26/2018 06:34 AM, Will Deacon wrote:
> Hi all,
>
> This is version three of the qspinlock patches I posted previously:
>
>   v1: https://lkml.org/lkml/2018/4/5/496
>   v2: https://lkml.org/lkml/2018/4/11/618
>
> Changes since v2 include:
>   * Fixed bisection issues
>   * Fixed x86 PV build
>   * Added patch proposing me as a co-maintainer
>   * Rebased onto -rc2
>
> All feedback welcome,
>
> Will
>
> --->8
>
> Jason Low (1):
>   locking/mcs: Use smp_cond_load_acquire() in mcs spin loop
>
> Waiman Long (1):
>   locking/qspinlock: Add stat tracking for pending vs slowpath
>
> Will Deacon (12):
>   barriers: Introduce smp_cond_load_relaxed and atomic_cond_read_relaxed
>   locking/qspinlock: Merge struct __qspinlock into struct qspinlock
>   locking/qspinlock: Bound spinning on pending->locked transition in
>     slowpath
>   locking/qspinlock/x86: Increase _Q_PENDING_LOOPS upper bound
>   locking/qspinlock: Remove unbounded cmpxchg loop from locking slowpath
>   locking/qspinlock: Kill cmpxchg loop when claiming lock from head of
>     queue
>   locking/qspinlock: Use atomic_cond_read_acquire
>   locking/qspinlock: Use smp_cond_load_relaxed to wait for next node
>   locking/qspinlock: Make queued_spin_unlock use smp_store_release
>   locking/qspinlock: Elide back-to-back RELEASE operations with
>     smp_wmb()
>   locking/qspinlock: Use try_cmpxchg instead of cmpxchg when locking
>   MAINTAINERS: Add myself as a co-maintainer for LOCKING PRIMITIVES
>
>  MAINTAINERS                               |   1 +
>  arch/x86/include/asm/qspinlock.h          |  21 ++-
>  arch/x86/include/asm/qspinlock_paravirt.h |   3 +-
>  include/asm-generic/atomic-long.h         |   2 +
>  include/asm-generic/barrier.h             |  27 +++-
>  include/asm-generic/qspinlock.h           |   2 +-
>  include/asm-generic/qspinlock_types.h     |  32 +++-
>  include/linux/atomic.h                    |   2 +
>  kernel/locking/mcs_spinlock.h             |  10 +-
>  kernel/locking/qspinlock.c                | 247 ++++++++++++++----------------
>  kernel/locking/qspinlock_paravirt.h       |  44 ++----
>  kernel/locking/qspinlock_stat.h           |   9 +-
>  12 files changed, 209 insertions(+), 191 deletions(-)
>
Other than my comment on patch 5 (which can wait as the code path is
unlikely to be used soon), I have no other issue with this patchset.

Acked-by: Waiman Long <longman@...hat.com>

Cheers,
Longman