linux-kernel - Re: [PATCH/RFC] remove irqs_disabled warning from local_bh

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Message-Id: <20080617.160839.112511197.davem@davemloft.net>
Date:	Tue, 17 Jun 2008 16:08:39 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	johannes@...solutions.net
Cc:	linux-kernel@...r.kernel.org, mb@...sch.de,
	david@...ntd.dyndns.org, linux-wireless@...r.kernel.org,
	mingo@...e.hu, torvalds@...ux-foundation.org
Subject: Re: [PATCH/RFC] remove irqs_disabled warning from local_bh_enable

From: Johannes Berg <johannes@...solutions.net>
Date: Tue, 17 Jun 2008 23:57:14 +0200

> This warning has started to trigger with mac80211 because it can, under
> some circumstances, use spin_lock_bh() protected sections within
> irq-disabled sections. Is that a bug?

It is a bug.  The only legal nesting is base --> BH --> IRQ locking.

> Also, if you're going to treat IRQs being enabled as a bug, there's no
> point in disabling them right afterwards, is there?

It's treating IRQs being "disabled" as a bug.  It expects them to
be enabled, always.

> If you're going to reject this patch, I'll post one that adds the
> warning to local_bh_enable_ip() to allow detecting this for everybody
> and not just those poor people running UP/NO-PREEMPT :)

That might be useful :)
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