linux-kernel - Re: [PATCH] Next branch: authgss: authgss.c: Fix warnings for uninitizlized variable expire

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Message-ID: <20140902132140.GA31793@fieldses.org>
Date:	Tue, 2 Sep 2014 09:21:40 -0400
From:	Bruce Fields <bfields@...ldses.org>
To:	Boaz Harrosh <openosd@...il.com>
Cc:	Trond Myklebust <trond.myklebust@...marydata.com>,
	Shakil A Khan <shakilk1729@...il.com>,
	Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
	Linux Kernel mailing list <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	William Andros Adamson <andros@...app.com>,
	Jeffrey Layton <jlayton@...marydata.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] Next branch: authgss: authgss.c: Fix warnings for
 uninitizlized variable expire

On Tue, Sep 02, 2014 at 01:52:15PM +0300, Boaz Harrosh wrote:
> On 09/01/2014 04:50 PM, Trond Myklebust wrote:
> > On Mon, Sep 1, 2014 at 7:32 AM, Shakil A Khan <shakilk1729@...il.com> wrote:
> >> Signed-off-by : Shakil A Khan <shakilk1729@...il.com>
> >> ---
> >>  net/sunrpc/auth_gss/auth_gss.c |    2 +-
> >>  1 files changed, 1 insertions(+), 1 deletions(-)
> >>
> >> diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
> >> index afb292c..bea0951 100644
> >> --- a/net/sunrpc/auth_gss/auth_gss.c
> >> +++ b/net/sunrpc/auth_gss/auth_gss.c
> >> @@ -1387,7 +1387,7 @@ gss_key_timeout(struct rpc_cred *rc)
> >>         struct gss_cred *gss_cred = container_of(rc, struct gss_cred, gc_base);
> >>         struct gss_cl_ctx *ctx;
> >>         unsigned long now = jiffies;
> >> -       unsigned long expire;
> >> +       unsigned long expire = 0;
> >>
> >>         rcu_read_lock();
> >>         ctx = rcu_dereference(gss_cred->gc_ctx);
> >> --
> >> 1.7.1
> > 
> > That would be a compiler bug, not a kernel bug. The kernel code is
> > perfectly correct as it stands, and will never access the
> > uninitialised variable.
> > 
> 
> Than you will need the infamous uninitialised_var()

You'd rather avoid sprinkling that all over, though.  If nothing else it
increases the chances you'll suppress a legimate warning some day.

And unless I'm missing something this one really does look like an
unambiguous compiler bug.

--b.

> 
> diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
> index afb292c..bea0951 100644
> --- a/net/sunrpc/auth_gss/auth_gss.c
> +++ b/net/sunrpc/auth_gss/auth_gss.c
> @@ -1387,7 +1387,7 @@ gss_key_timeout(struct rpc_cred *rc)
>  	struct gss_cred *gss_cred = container_of(rc, struct gss_cred, gc_base);
>  	struct gss_cl_ctx *ctx;
>  	unsigned long now = jiffies;
> -	unsigned long expire;
> +	unsigned long uninitialised_var(expire);
>  
>  	rcu_read_lock();
>  	ctx = rcu_dereference(gss_cred->gc_ctx);
> 
> Cheers
> Boaz
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