From: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
Russell King <linux@armlinux.org.uk>,
Ingo Molnar <mingo@redhat.com>, Waiman Long <longman@redhat.com>,
Will Deacon <will@kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFC PATCH 0/3] Queued spinlocks/RW-locks for ARM
Date: Tue, 8 Oct 2019 21:47:25 +0200 [thread overview]
Message-ID: <20191008194724.evlk3bnomcz3kxwg@flow> (raw)
In-Reply-To: <CAK8P3a0UH8_pSPbEd7fRjws-TZ=+q-gLQZXvEOtoX9YtZY9tmA@mail.gmail.com>
On 2019-10-08 16:32:27 [+0200], Arnd Bergmann wrote:
> On Tue, Oct 8, 2019 at 3:36 PM Waiman Long <longman@redhat.com> wrote:
> > In x86, the lock instruction prefix is patched out when running on UP
> > system. This downgrades the atomic cmpxchg to non-atomic one. We may do
> > something similar in other architectures.
>
> Unfortunately, the atomic macros cannot trivially be made cheaper
> on non-SMP systems based on load-locked/store-conditional
> based architectures, as there may be an interrupt in-between,
> and disabling interrupts would likely be more expensive.
>
> However, there might be a way to take a shortcut out of
> queued_spin_lock() using asm-goto combined with the ARM
> __ALT_SMP_ASM() macro.
The smp_xchg16_relaxed() snippet above looked good. I would buy it :)
Where are you heading with __ALT_SMP_ASM()?
> Arnd
Sebastian
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-10-08 19:47 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-07 21:44 [RFC PATCH 0/3] Queued spinlocks/RW-locks for ARM Sebastian Andrzej Siewior
2019-10-07 21:44 ` [PATCH 1/3] ARM: Use qrwlock implementation Sebastian Andrzej Siewior
2019-10-07 21:44 ` [PATCH 2/3] ARM: Use qspinlock implementation Sebastian Andrzej Siewior
2019-10-07 21:44 ` [PATCH 3/3] ARM: Inline locking functions for !PREEMPTION Sebastian Andrzej Siewior
2019-10-08 11:42 ` [RFC PATCH 0/3] Queued spinlocks/RW-locks for ARM Arnd Bergmann
2019-10-08 13:36 ` Waiman Long
2019-10-08 14:32 ` Arnd Bergmann
2019-10-08 19:47 ` Sebastian Andrzej Siewior [this message]
2019-10-08 21:47 ` Arnd Bergmann
2019-10-08 22:02 ` Sebastian Andrzej Siewior
2019-10-09 8:15 ` Arnd Bergmann
2019-10-09 8:46 ` Peter Zijlstra
2019-10-09 8:57 ` Arnd Bergmann
2019-10-09 9:31 ` Peter Zijlstra
2019-10-09 10:31 ` Arnd Bergmann
2019-10-09 10:56 ` Peter Zijlstra
2019-10-09 12:00 ` Arnd Bergmann
2019-10-09 12:06 ` Peter Zijlstra
2019-10-09 12:52 ` Will Deacon
2019-10-09 13:50 ` Arnd Bergmann
2019-10-09 21:42 ` Sebastian Andrzej Siewior
2019-10-08 19:32 ` Sebastian Andrzej Siewior
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191008194724.evlk3bnomcz3kxwg@flow \
--to=sebastian@breakpoint.cc \
--cc=arnd@arndb.de \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux@armlinux.org.uk \
--cc=longman@redhat.com \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.