Subject: Re: linux-next: build failure after merge of the akpm-current tree

From: "Luis R. Rodriguez" <[email-masked]>
Date: Thu, 26 Jun 2014 10:29:40 +0200

On Thu, Jun 26, 2014 at 04:22:57PM +1000, Stephen Rothwell wrote:
> Hi Andrew,
> 
> After merging the akpm tree, today's linux-next build (powerpc
> ppc44x_defconfig) failed like this:
> 
> kernel/printk/printk.c: In function 'log_buf_add_cpu':
> kernel/printk/printk.c:269:37: error: 'CONFIG_LOG_CPU_MAX_BUF_SHIFT' undeclared (first use in this function)
>  #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
>                                      ^
> kernel/printk/printk.c:864:42: note: in expansion of macro '__LOG_CPU_MAX_BUF_LEN'
>   cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
>                                           ^
> kernel/printk/printk.c:269:37: note: each undeclared identifier is reported only once for each function it appears in
>  #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
>                                      ^
> kernel/printk/printk.c:864:42: note: in expansion of macro '__LOG_CPU_MAX_BUF_LEN'
>   cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
>                                           ^
> 
> Caused by commit 58209adf633e ("printk: allow increasing the ring
> buffer depending on the number of CPUs").  CONFIG_LOG_CPU_MAX_BUF_SHIFT
> is not defined for this configuration.

diff --git a/init/Kconfig b/init/Kconfig
index 573d3f6..2339118 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -822,10 +822,9 @@ config LOG_BUF_SHIFT
 
 config LOG_CPU_MAX_BUF_SHIFT
 	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
-	range 0 21
-	default 12
-	depends on SMP
-	depends on !BASE_SMALL
+	range 0 21 if SMP && !BASE_SMALL
+	default 12 if SMP && !BASE_SMALL
+	default 0 if !SMP || BASE_SMALL
 	help
 	  The kernel ring buffer will get additional data logged onto it
 	  when multiple CPUs are supported. Typically the contributions are