All of lore.kernel.org
 help / color / mirror / Atom feed
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: nigel@nigel.suspend2.net, kexec@lists.infradead.org,
	linux-kernel@vger.kernel.org, rjw@sisk.pl,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	pavel@ucw.cz, ying.huang@intel.com, mingo@elte.hu,
	torvalds@linux-foundation.org, vgoyal@redhat.com
Subject: Re: [PATCH] kexec jump: fix compiling warning on xchg(&kexec_lock, 0) in kernel_kexec()
Date: Wed, 13 Aug 2008 16:15:04 -0400	[thread overview]
Message-ID: <1218658504.9042.61.camel@localhost> (raw)
In-Reply-To: <20080813124406.21091eae.akpm@linux-foundation.org>

On Wed, 2008-08-13 at 12:44 -0700, Andrew Morton wrote:

> - Is xchg() guaranteed to be atomic?  That's what atomic_xchg() is for.

Yes, xchg() is guaranteed to be atomic. atomic_xchg() applies only to
the atomic_t type, and is almost always #defined to xchg().

> - xchg() isn't guaranteed to exist on all architectures.  atomic_xchg() is.

You appear to be confusing xchg() with cmpxchg(). AFAIK, xchg() exists
on all architectures, and is used in several instances of generic code.
It is particularly extensively used in the networking layer.

Trond


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

WARNING: multiple messages have this Message-ID (diff)
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	torvalds@linux-foundation.org, ying.huang@intel.com,
	pavel@ucw.cz, nigel@nigel.suspend2.net, rjw@sisk.pl,
	vgoyal@redhat.com, mingo@elte.hu, linux-kernel@vger.kernel.org,
	kexec@lists.infradead.org
Subject: Re: [PATCH] kexec jump: fix compiling warning on xchg(&kexec_lock, 0) in kernel_kexec()
Date: Wed, 13 Aug 2008 16:15:04 -0400	[thread overview]
Message-ID: <1218658504.9042.61.camel@localhost> (raw)
In-Reply-To: <20080813124406.21091eae.akpm@linux-foundation.org>

On Wed, 2008-08-13 at 12:44 -0700, Andrew Morton wrote:

> - Is xchg() guaranteed to be atomic?  That's what atomic_xchg() is for.

Yes, xchg() is guaranteed to be atomic. atomic_xchg() applies only to
the atomic_t type, and is almost always #defined to xchg().

> - xchg() isn't guaranteed to exist on all architectures.  atomic_xchg() is.

You appear to be confusing xchg() with cmpxchg(). AFAIK, xchg() exists
on all architectures, and is used in several instances of generic code.
It is particularly extensively used in the networking layer.

Trond


  parent reply	other threads:[~2008-08-13 20:15 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-08-13  9:12 [PATCH] kexec jump: fix compiling warning on xchg(&kexec_lock, 0) in kernel_kexec() Huang Ying
2008-08-13  9:12 ` Huang Ying
2008-08-13  9:27 ` Andrew Morton
2008-08-13  9:27   ` Andrew Morton
2008-08-13 17:01   ` Linus Torvalds
2008-08-13 17:01     ` Linus Torvalds
2008-08-13 17:25     ` Andrew Morton
2008-08-13 17:25       ` Andrew Morton
2008-08-13 17:59       ` Ingo Molnar
2008-08-13 17:59         ` Ingo Molnar
2008-08-13 16:57 ` Linus Torvalds
2008-08-13 16:57   ` Linus Torvalds
2008-08-13 18:12   ` Eric W. Biederman
2008-08-13 18:12     ` Eric W. Biederman
2008-08-13 18:31     ` Vivek Goyal
2008-08-13 18:31       ` Vivek Goyal
2008-08-13 19:44     ` Andrew Morton
2008-08-13 19:44       ` Andrew Morton
2008-08-13 19:50       ` Linus Torvalds
2008-08-13 19:50         ` Linus Torvalds
2008-08-13 20:07         ` Andrew Morton
2008-08-13 20:07           ` Andrew Morton
2008-08-13 20:13           ` Linus Torvalds
2008-08-13 20:13             ` Linus Torvalds
2008-08-13 20:25             ` Andrew Morton
2008-08-13 20:25               ` Andrew Morton
2008-08-13 20:31               ` Linus Torvalds
2008-08-13 20:31                 ` Linus Torvalds
2008-08-13 20:41                 ` Andrew Morton
2008-08-13 20:41                   ` Andrew Morton
2008-08-13 21:21                   ` Vivek Goyal
2008-08-13 21:21                     ` Vivek Goyal
2008-08-13 22:17                   ` Linus Torvalds
2008-08-13 22:17                     ` Linus Torvalds
2008-08-13 20:15       ` Trond Myklebust [this message]
2008-08-13 20:15         ` Trond Myklebust

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=1218658504.9042.61.camel@localhost \
    --to=trond.myklebust@fys.uio.no \
    --cc=akpm@linux-foundation.org \
    --cc=ebiederm@xmission.com \
    --cc=kexec@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@elte.hu \
    --cc=nigel@nigel.suspend2.net \
    --cc=pavel@ucw.cz \
    --cc=rjw@sisk.pl \
    --cc=torvalds@linux-foundation.org \
    --cc=vgoyal@redhat.com \
    --cc=ying.huang@intel.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.