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    SubjectRe: [PATCH] kernel: audit.c: Add __rcu notation to RCU pointer
    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 <frextrite@gmail.com> 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 <frextrite@gmail.com>
    > > > > > ---
    > > > > > 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

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