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SubjectRe: [PATCH 0/6] Switch arm64 over to qrwlock
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Date
Hi,


On 10/05/2017 07:54 AM, Will Deacon wrote:
> Hi all,
>
> This patch series reworks bits of the qrwlock code that it can be used
> to replace the asm rwlocks currently implemented for arm64. The structure
> of the series is:
>
> Patches 1-3 : Work WFE into qrwlock using atomic_cond_read_acquire so
> we can avoid busy-waiting.
>
> Patch 4 : Enable qrwlocks for arm64
>
> Patch 5-6 : Ensure writer slowpath fairness. This has a potential
> performance impact on the writer unlock path, so I've
> kept them at the end.
>
> The patches apply on top of my other locking cleanups:
>
> http://lkml.kernel.org/r/1507055129-12300-1-git-send-email-will.deacon@arm.com
>
> although the conflict with mainline is trivial to resolve without those.
> The full stack is also pushed here:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git qrwlock
>
> All comments (particularly related to testing and performance) welcome!

I haven't done any perf testing, but the machines continue to boot, and
the stress-ng test which causes task lock problems with the normal arm64
rwlock now appears to run as expected. So, its a good start!



>
> Cheers,
>
> Will
>
> --->8
>
> Will Deacon (6):
> kernel/locking: Use struct qrwlock instead of struct __qrwlock
> locking/atomic: Add atomic_cond_read_acquire
> kernel/locking: Use atomic_cond_read_acquire when spinning in qrwlock
> arm64: locking: Move rwlock implementation over to qrwlocks
> kernel/locking: Prevent slowpath writers getting held up by fastpath
> kernel/locking: Remove unused union members from struct qrwlock
>
> arch/arm64/Kconfig | 17 ++++
> arch/arm64/include/asm/Kbuild | 1 +
> arch/arm64/include/asm/spinlock.h | 164 +-------------------------------
> arch/arm64/include/asm/spinlock_types.h | 6 +-
> include/asm-generic/atomic-long.h | 3 +
> include/asm-generic/qrwlock.h | 14 +--
> include/asm-generic/qrwlock_types.h | 2 +-
> include/linux/atomic.h | 4 +
> kernel/locking/qrwlock.c | 83 +++-------------
> 9 files changed, 43 insertions(+), 251 deletions(-)
>

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