Re: [PATCH] kernel: audit.c: Add __rcu notation to RCU pointer

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(a)gmail.com&gt; > > --- > > 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)