linux-kernel - RE: [RFC][PATCH] futex: Hide false positive about uninit var usage

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Date:	Tue, 16 Nov 2010 10:59:53 -0600
From:	"Aguirre, Sergio" <saaguirre@...com>
To:	Darren Hart <dvhart@...ux.intel.com>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Namhyung Kim <namhyung@...il.com>
Subject: RE: [RFC][PATCH] futex: Hide false positive about uninit var usage

Hi Darren,

> -----Original Message-----
> From: Darren Hart [mailto:dvhart@...ux.intel.com]
> Sent: Tuesday, November 16, 2010 10:43 AM
> To: Aguirre, Sergio
> Cc: LKML; Thomas Gleixner; Peter Zijlstra; Ingo Molnar; Namhyung Kim
> Subject: Re: [RFC][PATCH] futex: Hide false positive about uninit var
> usage
> 
> On 11/16/2010 08:32 AM, Sergio Aguirre wrote:
> > In exit_robust_list, there was this warning shown:
> >
> > kernel/futex.c: In function 'exit_robust_list':
> > kernel/futex.c:2492: warning: 'next_pi' may be used uninitialized in
> this function
> >
> > Which is a false positive, since in the function, the only scenario
> > possible in which the var is read, is after a successful excecution of
> > fetch_robust_entry, which populates the variable.
> >
> > So there's no real possibility of it being used uninitialized.
> 
> Hi Sergio,
> 
> You are correct. Thomas has recently pulled my fix for this into tip, it
> should be queued for mainline already.

Oh ok. Sorry, I didn't know that. Please ignore this patch then.

Regards,
Sergio

> 
> Thanks,
> 
> Darren Hart
> 
> >
> > Signed-off-by: Sergio Aguirre<saaguirre@...com>
> > Cc: Thomas Gleixner<tglx@...utronix.de>
> > Cc: Peter Zijlstra<a.p.zijlstra@...llo.nl>
> > Cc: Darren Hart<dvhart@...ux.intel.com>
> > Cc: Ingo Molnar<mingo@...e.hu>
> > Cc: Namhyung Kim<namhyung@...il.com>
> > ---
> >   kernel/futex.c |    3 ++-
> >   1 files changed, 2 insertions(+), 1 deletions(-)
> >
> > diff --git a/kernel/futex.c b/kernel/futex.c
> > index 6c683b3..3646157 100644
> > --- a/kernel/futex.c
> > +++ b/kernel/futex.c
> > @@ -2489,7 +2489,8 @@ void exit_robust_list(struct task_struct *curr)
> >   {
> >   	struct robust_list_head __user *head = curr->robust_list;
> >   	struct robust_list __user *entry, *next_entry, *pending;
> > -	unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
> > +	unsigned int limit = ROBUST_LIST_LIMIT, pi;
> > +	unsigned int uninitialized_var(next_pi), pip;
> >   	unsigned long futex_offset;
> >   	int rc;
> >
> 
> 
> --
> Darren Hart
> Yocto Linux Kernel
--
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