linux-kernel - Re: [PATCH] i386: Remove unneeded test of 'task' in dump

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Message-Id: <1394212900.25122.91826945.38D96F18@webmail.messagingengine.com>
Date:	Fri, 07 Mar 2014 18:21:40 +0100
From:	Alexander van Heukelum <heukelum@...tmail.fm>
To:	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Jesper Juhl <jesper.juhl@...il.com>
Subject: Re: [PATCH] i386: Remove unneeded test of 'task' in dump_trace() (again)

On Fri, Mar 7, 2014, at 16:52, Steven Rostedt wrote:
> 
> Commit 028a690a1ebc8b "i386: Remove unneeded test of 'task' in dump_trace()"
> correctly removed the unneeded 'task != NULL' check because it would
> be set to current if it was NULL.
> 
> Commit 2bc5f927d489 "i386: split out dumpstack code from traps_32.c"
> moved the code from traps_32.c to its own file dump_stack.c for
> preparation of the i386 / x86_64 merge.
> 
> Commit 8a541665b906 "dumpstack: x86: various small unification steps"
> worked to make i386 and x86_64 dump_stack logic similar. But this
> actually reverted the correct change from 028a690a1ebc8b.
> 
> Commit d0caf292505d "x86/dumpstack: Remove unneeded check in dump_trace()"
> removed the unneeded "task != NULL" check for x86_64 but left that same
> unneeded check for i386, that was added because x86_64 had it!
> 
> This chain of events ironically had i386 add back the unneeded task != NULL
> check because x86_64 did it, and then the fix for x86_64 was fixed
> by Dan. And even more ironically, it was Dan's smatch bot that told
> me that a change to dump_stack_32 I made may be wrong if current can
> be NULL (it can't), as there was a check for it by assigning task to
> current, and then checking if task is NULL.
> 
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> Cc: Jesper Juhl <jesper.juhl@...il.com>
> Cc: Alexander van Heukelum <heukelum@...tmail.fm>

Great archeology ;)

Acked-by: Alexander van Heukelum <heukelum@...tmail.fm>

> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> ---
>  arch/x86/kernel/dumpstack_32.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
> index dca820b..5abd4cd 100644
> --- a/arch/x86/kernel/dumpstack_32.c
> +++ b/arch/x86/kernel/dumpstack_32.c
> @@ -53,7 +53,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
>  		unsigned long dummy;
>  
>  		stack = &dummy;
> -		if (task && task != current)
> +		if (task != current)
>  			stack = (unsigned long *)task->thread.sp;
>  	}
>  
> -- 
> 1.8.1.4
> 
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