Re: [RFC][PATCH] futex: Hide false positive about uninit var usage

[Darren Hart]

On 11/16/2010 08:59 AM, Aguirre, Sergio wrote:
> Hi Darren,
>
> > -----Original Message-----
> > From: Darren Hart [mailto:dvhart@xxxxxxxxxxxxxxx]
> > 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.

No problem. In the future, if you run into problems with futexes, check 
the linux-2.6-tip repository for fixes as that is where they are queued 
up before going into mainline.

git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git
branch: core/futexes

Thanks,

Darren

> Regards,
> Sergio
>
> > Thanks,
> >
> > Darren Hart
> >
> > > Signed-off-by: Sergio Aguirre<saaguirre@xxxxxx>
> > > Cc: Thomas Gleixner<tglx@xxxxxxxxxxxxx>
> > > Cc: Peter Zijlstra<a.p.zijlstra@xxxxxxxxx>
> > > Cc: Darren Hart<dvhart@xxxxxxxxxxxxxxx>
> > > Cc: Ingo Molnar<mingo@xxxxxxx>
> > > Cc: Namhyung Kim<namhyung@xxxxxxxxx>
> > > ---
> > >    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


--
Darren Hart
Yocto Linux Kernel
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