All of lore.kernel.org
 help / color / mirror / Atom feed
From: "Jan Beulich" <jbeulich@novell.com>
To: <mingo@elte.hu>, "Peter Zijlstra" <peterz@infradead.org>,
	<tglx@linutronix.de>, <mingo@redhat.com>, <hpa@zytor.com>
Cc: <linux-kernel@vger.kernel.org>
Subject: Re: [tip:core/ipi] generic-ipi: eliminate spurious pointlessWARN_ON()s
Date: Fri, 13 Mar 2009 09:21:50 +0000	[thread overview]
Message-ID: <49BA33BE.76E4.0078.0@novell.com> (raw)
In-Reply-To: <1236934491.5188.209.camel@laptop>

>>> Peter Zijlstra <peterz@infradead.org> 13.03.09 09:54 >>>
>Wouldn't leaving them in place but changing them to:
>
>WARN_ON(irqs_disabled() && system_state == SYSTEM_RUNNING);
>
>be clearer?

I don't think that would be precise: system_state gets set to
SYSTEM_RUNNING much later than APs get brought up (i.e. there are
cases where the WARN_ON()s could validly trigger with SYSTEM_BOOTING),
and also doesn't cover states > SYSTEM_RUNNING (where, again, after
perhaps having brought down all APs the warnings could become pointless,
but the warnings could be meaningful as long as there are still some APs
online).

While from an abstract code reading perspective your suggestion might
seem reasonable, the changed placement really reflects what the warning
is trying to warn about - a potential deadlock which cannot occur under
the conditions filtered out by conditionals the warnings were moved
beyond.

Jan


  reply	other threads:[~2009-03-13  9:25 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-03-12 13:21 [PATCH, resend] eliminate spurious pointless WARN_ON()s Jan Beulich
2009-03-12 13:48 ` Andi Kleen
2009-03-13  8:52   ` Peter Zijlstra
2009-03-13  1:39 ` [tip:core/ipi] generic-ipi: " Jan Beulich
2009-03-13  8:54   ` Peter Zijlstra
2009-03-13  9:21     ` Jan Beulich [this message]
2009-03-13  9:43       ` [tip:core/ipi] generic-ipi: eliminate spurious pointlessWARN_ON()s Peter Zijlstra
2009-03-13 10:38         ` Ingo Molnar
2009-03-19 22:14           ` Eric W. Biederman
2009-03-20  8:52             ` Ingo Molnar
2009-03-20  9:58               ` Eric W. Biederman
2009-03-20 18:24                 ` Ingo Molnar
2009-03-20 18:52                   ` Peter Zijlstra
2009-03-20 19:34                     ` cpu hotplug and lockdep (was: Re: [tip:core/ipi] generic-ipi: eliminate spurious pointlessWARN_ON()s) Peter Zijlstra
2009-03-21  7:39                       ` [PATCH 0/2] sysctl: lockdep support Eric W. Biederman
2009-03-21  7:40                         ` [PATCH 1/2] sysctl: Don't take the use count of multiple heads at a time Eric W. Biederman
2009-03-21  7:42                           ` [PATCH 2/2] sysctl: lockdep support for sysctl reference counting Eric W. Biederman
2009-03-30 22:26                             ` Andrew Morton
2009-03-30 22:53                               ` Eric W. Biederman
2009-03-30 23:18                                 ` Andrew Morton
2009-03-30 23:50                                   ` Eric W. Biederman
2009-03-31  8:10                               ` Peter Zijlstra
2009-03-31  8:47                                 ` Eric W. Biederman
2009-03-31  8:17                             ` Peter Zijlstra
2009-03-31 13:40                               ` Eric W. Biederman
2009-03-31 15:35                                 ` Peter Zijlstra
2009-03-31 22:44                                   ` Eric W. Biederman
2009-04-10  9:18                             ` Andrew Morton
2009-03-20 23:40                     ` [tip:core/ipi] generic-ipi: eliminate spurious pointlessWARN_ON()s Eric W. Biederman
2009-03-21 10:20                       ` Peter Zijlstra
2009-03-13  9:31     ` [tip:core/ipi] generic-ipi: eliminate spurious pointless WARN_ON()s Ingo Molnar
2009-03-13 10:36 ` [tip:core/ipi] generic-ipi: eliminate WARN_ON()s during oops/panic Ingo Molnar
2009-03-13 10:36 ` [tip:core/ipi] panic: decrease oops_in_progress only after having done the panic Ingo Molnar
2009-03-13 10:36 ` [tip:core/ipi] panic, smp: provide smp_send_stop() wrapper on UP too Ingo Molnar
2009-03-13 10:36 ` [tip:core/ipi] panic: clean up kernel/panic.c Ingo Molnar

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=49BA33BE.76E4.0078.0@novell.com \
    --to=jbeulich@novell.com \
    --cc=hpa@zytor.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@elte.hu \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=tglx@linutronix.de \
    /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.