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Fri, 29 Nov 2019 12:08:18 -0800 (PST) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id y6sm23937455pfm.12.2019.11.29.12.08.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 29 Nov 2019 12:08:18 -0800 (PST) Date: Fri, 29 Nov 2019 15:08:17 -0500 From: Joel Fernandes To: Amol Grover Cc: Paul Moore , Eric Paris , linux-kernel-mentees@lists.linuxfoundation.org, Shuah Khan , linux-audit@redhat.com, LKML Subject: Re: [PATCH] kernel: audit.c: Add __rcu notation to RCU pointer Message-ID: <20191129200817.GB239292@google.com> References: <20191126172723.GA12759@workstation-kernel-dev> <20191127022925.GB157739@google.com> <20191127052827.GA9782@workstation-portable> <20191128150949.GA30181@workstation-portable> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191128150949.GA30181@workstation-portable> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 28, 2019 at 08:39:49PM +0530, Amol Grover wrote: > On Wed, Nov 27, 2019 at 10:25:57AM -0500, Joel Fernandes wrote: > > On Wed, Nov 27, 2019 at 12:29 AM Amol Grover wrote: > > > > > > On Tue, Nov 26, 2019 at 09:29:25PM -0500, Joel Fernandes wrote: > > > > On Tue, Nov 26, 2019 at 10:57:23PM +0530, Amol Grover wrote: > > > > > add __rcu notation to RCU protected global pointer auditd_conn > > > > > > > > > > Fixes multiple instances of sparse error: > > > > > error: incompatible types in comparison expression > > > > > (different address spaces) > > > > > > > > > > Signed-off-by: Amol Grover > > > > > --- > > > > > kernel/audit.c | 6 ++++-- > > > > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > > > > > > > diff --git a/kernel/audit.c b/kernel/audit.c > > > > > index da8dc0db5bd3..30e7fc9b8da2 100644 > > > > > --- a/kernel/audit.c > > > > > +++ b/kernel/audit.c > > > > > @@ -102,12 +102,14 @@ struct audit_net { > > > > > * This struct is RCU protected; you must either hold the RCU lock for reading > > > > > * or the associated spinlock for writing. > > > > > */ > > > > > -static struct auditd_connection { > > > > > +struct auditd_connection { > > > > > struct pid *pid; > > > > > u32 portid; > > > > > struct net *net; > > > > > struct rcu_head rcu; > > > > > -} *auditd_conn = NULL; > > > > > +}; > > > > > +static struct auditd_connection __rcu *auditd_conn; > > > > > +RCU_INIT_POINTER(auditd_conn); > > > > > > > > Looks like this causes a build error. Always please build test your patches > > > > in the very least. And I also did not understand how RCU_INIT_POINTER can > > > > even be used outside of a function. In C, executable code cannot be outside > > > > functions. > > > > > > > > Is doing the following not sufficient to fix the sparse issue? > > > > > > > > thanks, > > > > > > > > - Joel > > > > > > > > ---8<----------------------- > > > > > > > > diff --git a/kernel/audit.c b/kernel/audit.c > > > > index 49b6049b26ac..c5d4b5a2dea1 100644 > > > > --- a/kernel/audit.c > > > > +++ b/kernel/audit.c > > > > @@ -108,8 +108,8 @@ struct auditd_connection { > > > > struct net *net; > > > > struct rcu_head rcu; > > > > }; > > > > -static struct auditd_connection __rcu *auditd_conn; > > > > -RCU_INIT_POINTER(auditd_conn); > > > > +static struct auditd_connection __rcu *auditd_conn = NULL; > > > > > > I ran a quick checkpatch and it gave me this error: > > > ERROR: do not initialise statics to NULL > > > > > > So in order to fix it I decided to INIT the pointer (and failed) > > > > Well, try to understand the checkpatch error then, and do the right thing :) > > I read-up a few articles about this. I think I've understood the problem. I'm > sending in the ammended patch now. Sorry for this. Won't happen again. Oh, no need apology. You are learning. But yeah always do a thorough job before sending patches. thanks, - Joel