Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32

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To: Christoph Müllner <christophm30@xxxxxxxxx>
Subject: Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Wed, 7 Apr 2021 17:52:36 +0200
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>, Guo Ren <guoren@xxxxxxxxxx>, linux-riscv <linux-riscv@xxxxxxxxxxxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, linux-csky@xxxxxxxxxxxxxxx, linux-arch <linux-arch@xxxxxxxxxxxxxxx>, Guo Ren <guoren@xxxxxxxxxxxxxxxxx>, Will Deacon <will@xxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Waiman Long <longman@xxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, Anup Patel <anup@xxxxxxxxxxxxxx>
In-reply-to: <CAHB2gtROGuoNzv5f9QrhWX=3ZtZmUM=SAjYhKqP7dTiTTQwkqA@mail.gmail.com>
References: <1616868399-82848-4-git-send-email-guoren@kernel.org> <YGGGqftfr872/4CU@hirez.programming.kicks-ass.net> <CAJF2gTQNV+_txMHJw0cmtS-xcnuaCja-F7XBuOL_J0yN39c+uQ@mail.gmail.com> <YGG5c4QGq6q+lKZI@hirez.programming.kicks-ass.net> <CAJF2gTQUe237NY-kh+4_Yk4DTFJmA5_xgNQ5+BMpFZpUDUEYdw@mail.gmail.com> <YGHM2/s4FpWZiEQ6@hirez.programming.kicks-ass.net> <CAJF2gTS4jexKsSiXBY=5rz53LjcLUZ1K4pxjYJDVQCWx_8JTuA@mail.gmail.com> <YGwKpmPkn5xIxIyx@hirez.programming.kicks-ass.net> <20210407094224.GA3393992@infradead.org> <CAHB2gtROGuoNzv5f9QrhWX=3ZtZmUM=SAjYhKqP7dTiTTQwkqA@mail.gmail.com>

On Wed, Apr 07, 2021 at 04:29:12PM +0200, Christoph Müllner wrote:
> The comparison with sparc64 is not applicable, as sparc64 does not
> have LL/SC instructions.

Sparc64 has CAS, without hardware fwd progress. It has to do software
backoff for failed CAS in order to do software fwd progress.

Follow-Ups:
- Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
  - From: Peter Zijlstra

References:
- [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
  - From: guoren
- Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
  - From: Peter Zijlstra
- Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
  - From: Guo Ren
- Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
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- Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
  - From: Guo Ren
- Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
  - From: Peter Zijlstra
- Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
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- Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
  - From: Peter Zijlstra
- Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
  - From: Christoph Hellwig
- Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
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