All of lore.kernel.org
 help / color / mirror / Atom feed
From: Baoquan He <bhe@redhat.com>
To: Uros Bizjak <ubizjak@gmail.com>
Cc: akpm@linux-foundation.org, kexec@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	Eric Biederman <ebiederm@xmission.com>
Subject: Re: [PATCH] kexec: Use atomic_try_cmpxchg_acquire() in kexec_trylock()
Date: Mon, 22 Jul 2024 18:30:36 +0800	[thread overview]
Message-ID: <Zp40zOw+E1Na/Lly@MiWiFi-R3L-srv> (raw)
In-Reply-To: <CAFULd4Y8vhcTWG-eNMSLEJHR_1=LuQzKj7q4JX8Kv7auJKAYDQ@mail.gmail.com>

On 07/22/24 at 10:53am, Uros Bizjak wrote:
> On Mon, Jul 22, 2024 at 5:09 AM Baoquan He <bhe@redhat.com> wrote:
> >
> > On 07/19/24 at 12:38pm, Uros Bizjak wrote:
> > > Use atomic_try_cmpxchg_acquire(*ptr, &old, new) instead of
> > > atomic_cmpxchg_acquire(*ptr, old, new) == old in kexec_trylock().
> > > x86 CMPXCHG instruction returns success in ZF flag, so
> > > this change saves a compare after cmpxchg.
> >
> > Seems it can simplify code even though on non-x86 arch, should we
> > replace atomic_try_cmpxchg_acquire() with atomic_try_cmpxchg_acquire()
> > in all similar places?
> 
> Yes, the change is beneficial also for non-x86 architectures, please
> see analysis at thread [1]. I've been looking through the kernel
> sources for these places for quite some time, and I believe I have
> changed most of the places. The change is relatively straightforward,
> and immediately results in a better code.
> 
> [1] https://lore.kernel.org/lkml/871qwgmqws.fsf@mpe.ellerman.id.au/

Good to know, thanks for telling.


_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

WARNING: multiple messages have this Message-ID (diff)
From: Baoquan He <bhe@redhat.com>
To: Uros Bizjak <ubizjak@gmail.com>
Cc: akpm@linux-foundation.org, kexec@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	Eric Biederman <ebiederm@xmission.com>
Subject: Re: [PATCH] kexec: Use atomic_try_cmpxchg_acquire() in kexec_trylock()
Date: Mon, 22 Jul 2024 18:30:36 +0800	[thread overview]
Message-ID: <Zp40zOw+E1Na/Lly@MiWiFi-R3L-srv> (raw)
In-Reply-To: <CAFULd4Y8vhcTWG-eNMSLEJHR_1=LuQzKj7q4JX8Kv7auJKAYDQ@mail.gmail.com>

On 07/22/24 at 10:53am, Uros Bizjak wrote:
> On Mon, Jul 22, 2024 at 5:09 AM Baoquan He <bhe@redhat.com> wrote:
> >
> > On 07/19/24 at 12:38pm, Uros Bizjak wrote:
> > > Use atomic_try_cmpxchg_acquire(*ptr, &old, new) instead of
> > > atomic_cmpxchg_acquire(*ptr, old, new) == old in kexec_trylock().
> > > x86 CMPXCHG instruction returns success in ZF flag, so
> > > this change saves a compare after cmpxchg.
> >
> > Seems it can simplify code even though on non-x86 arch, should we
> > replace atomic_try_cmpxchg_acquire() with atomic_try_cmpxchg_acquire()
> > in all similar places?
> 
> Yes, the change is beneficial also for non-x86 architectures, please
> see analysis at thread [1]. I've been looking through the kernel
> sources for these places for quite some time, and I believe I have
> changed most of the places. The change is relatively straightforward,
> and immediately results in a better code.
> 
> [1] https://lore.kernel.org/lkml/871qwgmqws.fsf@mpe.ellerman.id.au/

Good to know, thanks for telling.


  reply	other threads:[~2024-07-22 10:30 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-07-19 10:38 [PATCH] kexec: Use atomic_try_cmpxchg_acquire() in kexec_trylock() Uros Bizjak
2024-07-19 10:38 ` Uros Bizjak
2024-07-22  3:09 ` Baoquan He
2024-07-22  3:09   ` Baoquan He
2024-07-22  8:53   ` Uros Bizjak
2024-07-22  8:53     ` Uros Bizjak
2024-07-22 10:30     ` Baoquan He [this message]
2024-07-22 10:30       ` Baoquan He

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=Zp40zOw+E1Na/Lly@MiWiFi-R3L-srv \
    --to=bhe@redhat.com \
    --cc=akpm@linux-foundation.org \
    --cc=ebiederm@xmission.com \
    --cc=kexec@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=ubizjak@gmail.com \
    /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.