linux-kernel - [PATCH] preempt: fix kernel build with !CONFIG

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Date:	Thu, 28 Oct 2010 13:20:44 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	linux-kernel@...r.kernel.org, Avi Kivity <avi@...hat.com>,
	Brian Gerst <brgerst@...il.com>,
	David Howells <dhowells@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Pekka Enberg <penberg@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Venkatesh Pallipadi <venki@...gle.com>, x86@...nel.org
Subject: [PATCH] preempt: fix kernel build with !CONFIG_BKL

The preempt count logic tries to take the BKL into account, which breaks
when CONFIG_BKL is not set.

Use the same preempt_count offset that we use without CONFIG_PREEMPT
when CONFIG_BKL is disabled.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Reported-by: "Kirill A. Shutemov" <kirill@...temov.name>

---
> /home/kas/git/tmp/linux-2.6-local/arch/x86/include/asm/i387.h: In function ‘irq_ts_save’:
> /home/kas/git/tmp/linux-2.6-local/arch/x86/include/asm/i387.h:324: error: implicit declaration of function ‘kernel_locked’
> make[1]: *** [arch/x86/kernel/asm-offsets.s] Error 1
> make: *** [prepare0] Error 2

Ah, found it. I had not considered or tested the case of CONFIG_BKL=n
with CONFIG_PREEMPT=y.

Does this work? Ideally please test with LOCKDEP enabled to see if
there are other problems in this configuration that I missed.

--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -96,7 +96,7 @@
  */
 #define in_nmi()	(preempt_count() & NMI_MASK)
 
-#if defined(CONFIG_PREEMPT)
+#if defined(CONFIG_PREEMPT) && defined(CONFIG_BKL)
 # define PREEMPT_INATOMIC_BASE kernel_locked()
 # define PREEMPT_CHECK_OFFSET 1
 #else
--
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