Re: linux-next: build failure after merge of the rcu tree

From: Borislav Petkov
Date: Mon Apr 13 2015 - 07:08:45 EST

On Mon, Apr 13, 2015 at 08:39:17PM +1000, Stephen Rothwell wrote:
> Hi Paul,
> After merging the rcu tree, today's linux-next build (powerpc allnoconfig)
> failed like this:
> init/main.c: In function 'rest_init':
> init/main.c:387:2: error: implicit declaration of function 'smpboot_thread_init' [-Werror=implicit-function-declaration]
> smpboot_thread_init();
> ^
> Caused by commit c55f6e1f6f69 ("cpu: Defer smpboot kthread unparking
> until CPU known to scheduler"). The declaration in include/linux/cpu.h
> is protected by CONFIG_SMP, its use is not.
> I have reverted that commit for today.

Thanks for the report Stephen, I know today is the day of b0rked
linux-next builds :-(

I think Ingo merged Paul's patch already so here's a fix ontop:

From: Borislav Petkov <bp@xxxxxxx>
Date: Mon, 13 Apr 2015 13:01:32 +0200
Subject: [PATCH] smpboot: Fix CONFIG_SMP=n build

Stephen Rothwell reported a CONFIG_SMP=n breakage with latest rcu/next.
The timing of this is very unfortunate as we've been hunting this bug
hastily over the weekend, just to be in time for the merge window.

So here's a fix ontop.

Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: <x86@xxxxxxxxxx>
include/linux/cpu.h | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 091badf0f6ba..bbdee1e6cf48 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -198,6 +198,10 @@ static inline void __unregister_cpu_notifier(struct notifier_block *nb)

+static inline void smpboot_thread_init(void)
static inline void cpu_maps_update_begin(void)


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