linux-kernel - Re: [PATCH-tip v2 00/10] locking/rwsem: Rwsem rearchitecture part 1

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Date:   Tue, 26 Feb 2019 10:20:13 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Waiman Long <longman@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>
Subject: Re: [PATCH-tip v2 00/10] locking/rwsem: Rwsem rearchitecture part 1

On Fri, 15 Feb 2019, Waiman Long wrote:

> v2:
>  - Sync up to v4 of the part 0 patch.
>  - Remove the rwsem.h->rwsem-xadd.h renaming patch & change patches
>    to modify rwsem.h instead of rwsem-xadd.h.
>  - Add a new patch to micro-optimize rwsem_try_read_lock_unqueued().
>
>This is part 1 of a 3-part (0/1/2) series to rearchitect the internal
>operation of rwsem. This depends on the v4 part 0 patches sent out
>previously
>
>https://lore.kernel.org/lkml/1550095217-12047-1-git-send-email-longman@redhat.com
>
>This part lays the foundation for part 2 without making any functional
>changes. This part includes the following changes:
>
> 1) Move code around and micro-optimize rwsem_try_read_lock_unqueued()
>    (patches 1-4).
> 2) Enhance the DEBUG_RWSEMS_WARN_ON() macro to provide more information
>    and add additional checks (patches 5 & 6).
> 3) Make the core qspinlock_stat.h code generic (lock event counting)
>    so that it can be used by all the architectures as well as other
>    locking subsystems such as rwsem (patches 7-10). Lock event
>    counting help us visualize how frequently a code path is being
>    used as well as spotting abnormal behavior due to bugs in the code
>    without noticeably affecting kernel performance and hence behavior.
>
>Both (2) and (3) are useful debugging aids.

Yes, this will come in handy in the future. Feel free to add my:

Acked-by: Davidlohr Bueso <dbueso@...e.de>

Thanks.