linux-kernel - Re: [PATCH] FRV: Fix no-hardware-breakpoint case

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Message-ID: <20091215072439.GA14651@elte.hu>
Date:	Tue, 15 Dec 2009 08:24:39 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	David Howells <dhowells@...hat.com>
Cc:	torvalds@...l.org, akpm@...ux-foundation.org, fweisbec@...il.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] FRV: Fix no-hardware-breakpoint case


* David Howells <dhowells@...hat.com> wrote:

> If there is no hardware breakpoint support, modify_user_hw_breakpoint() tries
> to return a NULL pointer through as an 'int' return value:
> 
> In file included from kernel/exit.c:53:
> include/linux/hw_breakpoint.h: In function 'modify_user_hw_breakpoint':
> include/linux/hw_breakpoint.h:96: warning: return makes integer from pointer without a cast
> 
> Return 0 instead.
> 
> Signed-off-by: David Howells <dhowells@...hat.com>
> ---
> 
>  include/linux/hw_breakpoint.h |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> 
> diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h
> index 69f07a9..e268388 100644
> --- a/include/linux/hw_breakpoint.h
> +++ b/include/linux/hw_breakpoint.h
> @@ -93,7 +93,7 @@ register_user_hw_breakpoint(struct perf_event_attr *attr,
>  			    struct task_struct *tsk)	{ return NULL; }
>  static inline int
>  modify_user_hw_breakpoint(struct perf_event *bp,
> -			  struct perf_event_attr *attr)	{ return NULL; }
> +			  struct perf_event_attr *attr)	{ return 0; }

Note, this patch is wrong as it only papers over the warning without 
understanding the underlying bug: the right fix is to return an error code.

The latest perf update has the right fix - AFAICS Linus did the conflict 
resolution correctly so upstream should be fine.

	Ingo
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