From: ebiederm@xmission.com (Eric W. Biederman)
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Huang Ying <ying.huang@intel.com>, Pavel Machek <pavel@ucw.cz>,
nigel@nigel.suspend2.net, "Rafael J. Wysocki" <rjw@sisk.pl>,
Vivek Goyal <vgoyal@redhat.com>,
mingo@elte.hu, Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org,
Kexec Mailing List <kexec@lists.infradead.org>
Subject: Re: [PATCH -v3 1/7] kexec jump: clean up #ifdef and comments
Date: Tue, 12 Aug 2008 21:47:22 -0700 [thread overview]
Message-ID: <m1ej4tikrp.fsf@frodo.ebiederm.org> (raw)
In-Reply-To: <20080812204900.db63deaa.akpm@linux-foundation.org> (Andrew Morton's message of "Tue, 12 Aug 2008 20:49:00 -0700")
Andrew Morton <akpm@linux-foundation.org> writes:
> On Tue, 12 Aug 2008 11:14:21 +0800 Huang Ying <ying.huang@intel.com> wrote:
>
>> xchg(&kexec_lock, 0);
>
> kernel/kexec.c: In function 'kernel_kexec':
> kernel/kexec.c:1501: warning: value computed is not used
A good question is why we are warned.
> Is there any reason why we cannot use the more conventional
> test_and_set_bit() etc, rather than this peculiarity?
>
> Or perhaps spin_trylock?
Totally odd.
Let me stop and take a look and see what has been changed. The original
code used a xchg based read copy update scheme, which was extremely
compatible with a lot of goals. The primary one being no blocking paths
in a successful kexec, and minimal dependence on library functions.
We need that minimal dependence to handle the kexec on panic case.
That doesn't rule out something like test_and_set_bit.
Eric
prev parent reply other threads:[~2008-08-13 4:53 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-12 3:14 [PATCH -v3 1/7] kexec jump: clean up #ifdef and comments Huang Ying
2008-08-13 3:49 ` Andrew Morton
2008-08-13 4:44 ` Huang Ying
2008-08-13 4:47 ` Eric W. Biederman [this message]
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=m1ej4tikrp.fsf@frodo.ebiederm.org \
--to=ebiederm@xmission.com \
--cc=akpm@linux-foundation.org \
--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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox