Return-Path: Received: from fieldses.org ([173.255.197.46]:44931 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753878AbbJIULE (ORCPT ); Fri, 9 Oct 2015 16:11:04 -0400 Date: Fri, 9 Oct 2015 16:10:59 -0400 From: "J. Bruce Fields" To: Arnd Bergmann Cc: Trond Myklebust , linux-nfs@vger.kernel.org, Anna Schumaker , Jeff Layton , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] sunrpc: avoid warning in gss_key_timeout Message-ID: <20151009201059.GC8188@fieldses.org> References: <6995148.OQIKcAcqHW@wuerfel> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <6995148.OQIKcAcqHW@wuerfel> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, Oct 09, 2015 at 04:13:45PM +0200, Arnd Bergmann wrote: > The gss_key_timeout() function causes a harmless warning in some > configurations, e.g. ARM imx_v6_v7_defconfig with gcc-5.2, if the > compiler cannot figure out the state of the 'expire' variable across > an rcu_read_unlock(): > > net/sunrpc/auth_gss/auth_gss.c: In function 'gss_key_timeout': > net/sunrpc/auth_gss/auth_gss.c:1422:211: warning: 'expire' may be used uninitialized in this function [-Wmaybe-uninitialized] > > To avoid this warning without adding a bogus initialization, this > rewrites the function so the comparison is done inside of the > critical section. As a side-effect, it also becomes slightly > easier to understand because the implementation now more closely > resembles the comment above it. Looks reasonable, thanks; applying for 4.4--b. > > Signed-off-by: Arnd Bergmann > Fixes: c5e6aecd034e7 ("sunrpc: fix RCU handling of gc_ctx field") > > diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c > index dace13d7638e..799e65b944b9 100644 > --- a/net/sunrpc/auth_gss/auth_gss.c > +++ b/net/sunrpc/auth_gss/auth_gss.c > @@ -1411,17 +1411,16 @@ 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 timeout = jiffies + (gss_key_expire_timeo * HZ); > + int ret = 0; > > rcu_read_lock(); > ctx = rcu_dereference(gss_cred->gc_ctx); > - if (ctx) > - expire = ctx->gc_expiry - (gss_key_expire_timeo * HZ); > + if (!ctx || time_after(timeout, ctx->gc_expiry)) > + ret = -EACCES; > rcu_read_unlock(); > - if (!ctx || time_after(now, expire)) > - return -EACCES; > - return 0; > + > + return ret; > } > > static int