Re: [PATCH rdma-next] IB/core: Avoid deadlock during netlink message handling

[Leon Romanovsky <leon@kernel.org>]

On Thu, Oct 24, 2019 at 10:17:43AM -0300, Jason Gunthorpe wrote:
> On Tue, Oct 15, 2019 at 11:07:33AM +0300, Leon Romanovsky wrote:
>
> > diff --git a/drivers/infiniband/core/netlink.c b/drivers/infiniband/core/netlink.c
> > index 81dbd5f41bed..a3507b8be569 100644
> > +++ b/drivers/infiniband/core/netlink.c
> > @@ -42,9 +42,12 @@
> >  #include <linux/module.h>
> >  #include "core_priv.h"
> >
> > -static DEFINE_MUTEX(rdma_nl_mutex);
> >  static struct {
> > -	const struct rdma_nl_cbs   *cb_table;
> > +	const struct rdma_nl_cbs __rcu *cb_table;
> > +	/* Synchronizes between ongoing netlink commands and netlink client
> > +	 * unregistration.
> > +	 */
> > +	struct srcu_struct unreg_srcu;
>
> A srcu in every index is serious overkill for this. Lets just us a
> rwsem:

I liked previous variant more than rwsem, but it is Parav's patch.

Thanks