linux-kernel - Re: [PATCH v2] rcu: ensure kernel/rcu/rcu.h can be sourced/used stand-alone

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Message-ID: <20140220015317.GL4250@linux.vnet.ibm.com>
Date:	Wed, 19 Feb 2014 17:53:17 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:	Dipankar Sarma <dipankar@...ibm.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] rcu: ensure kernel/rcu/rcu.h can be sourced/used
 stand-alone

On Wed, Feb 19, 2014 at 02:33:27PM -0500, Paul Gortmaker wrote:
> The kbuild test bot uncovered an implicit dependence on the
> trace header being present before rcu.h in ia64 allmodconfig
> that looks like this:
> 
> In file included from kernel/ksysfs.c:22:0:
> kernel/rcu/rcu.h: In function '__rcu_reclaim':
> kernel/rcu/rcu.h:107:3: error: implicit declaration of function 'trace_rcu_invoke_kfree_callback' [-Werror=implicit-function-declaration]
> kernel/rcu/rcu.h:112:3: error: implicit declaration of function 'trace_rcu_invoke_callback' [-Werror=implicit-function-declaration]
> cc1: some warnings being treated as errors
> 
> Looking at other rcu.h users, we can find that they all
> were sourcing the trace header in advance of rcu.h itself,
> as seen in the context of this diff.  There were also some
> inconsistencies as to whether it was or wasn't sourced based
> on the parent tracing Kconfig.
> 
> Rather than "fix" it at each use site, and have inconsistent
> use based on whether "#ifdef CONFIG_RCU_TRACE" was used or not,
> lets just source the trace header just once, in the actual consumer
> of it, which is rcu.h itself.  We include it unconditionally, as
> build testing shows us that is a hard requirement for some files.
> 
> Reported-by: kbuild test robot <fengguang.wu@...el.com>
> Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>

Queued for 3.16, thank you, Paul!

							Thanx, Paul

> ---
> 
> [v2: move the #include <trace/events/rcu.h> outside of the scope
>  of #ifdef CONFIG_RCU_TRACE so it is unconditionally included.]
> 
>  kernel/rcu/rcu.h    | 1 +
>  kernel/rcu/srcu.c   | 2 --
>  kernel/rcu/tiny.c   | 4 ----
>  kernel/rcu/tree.c   | 2 --
>  kernel/rcu/update.c | 1 -
>  5 files changed, 1 insertion(+), 9 deletions(-)
> 
> diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
> index 1bd787fddcb2..3d2a037332b2 100644
> --- a/kernel/rcu/rcu.h
> +++ b/kernel/rcu/rcu.h
> @@ -23,6 +23,7 @@
>  #ifndef __LINUX_RCU_H
>  #define __LINUX_RCU_H
> 
> +#include <trace/events/rcu.h>
>  #ifdef CONFIG_RCU_TRACE
>  #define RCU_TRACE(stmt) stmt
>  #else /* #ifdef CONFIG_RCU_TRACE */
> diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
> index 5db7e9272d37..8e66b05bfd82 100644
> --- a/kernel/rcu/srcu.c
> +++ b/kernel/rcu/srcu.c
> @@ -36,8 +36,6 @@
>  #include <linux/delay.h>
>  #include <linux/srcu.h>
> 
> -#include <trace/events/rcu.h>
> -
>  #include "rcu.h"
> 
>  /*
> diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
> index 53b95bbf4abb..d9efcc13008c 100644
> --- a/kernel/rcu/tiny.c
> +++ b/kernel/rcu/tiny.c
> @@ -37,10 +37,6 @@
>  #include <linux/prefetch.h>
>  #include <linux/ftrace_event.h>
> 
> -#ifdef CONFIG_RCU_TRACE
> -#include <trace/events/rcu.h>
> -#endif /* #else #ifdef CONFIG_RCU_TRACE */
> -
>  #include "rcu.h"
> 
>  /* Forward declarations for tiny_plugin.h. */
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index c7a00dbe768b..351faba48b91 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -58,8 +58,6 @@
>  #include <linux/suspend.h>
> 
>  #include "tree.h"
> -#include <trace/events/rcu.h>
> -
>  #include "rcu.h"
> 
>  MODULE_ALIAS("rcutree");
> diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
> index fd0d5b5b8e7c..4c0a9b0af469 100644
> --- a/kernel/rcu/update.c
> +++ b/kernel/rcu/update.c
> @@ -49,7 +49,6 @@
>  #include <linux/module.h>
> 
>  #define CREATE_TRACE_POINTS
> -#include <trace/events/rcu.h>
> 
>  #include "rcu.h"
> 
> -- 
> 1.8.5.2
> 

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