On Mon, Mar 24, 2014 at 07:11:44AM -0400, Neil Horman wrote:
> On Mon, Mar 24, 2014 at 12:42:46AM +0530, Monam Agarwal wrote:
> > This patch replaces rcu_assign_pointer(x, NULL) with RCU_INIT_POINTER(x,
> > NULL)
> >
> > The rcu_assign_pointer() ensures that the initialization of a structure
> >
> > is carried out before storing a pointer to that structure.
> > And in the case of the NULL pointer, there is no structure to initialize.
> > So, rcu_assign_pointer(p, NULL) can be safely converted to
> > RCU_INIT_POINTER(p, NULL)
> >
> > Signed-off-by: Monam Agarwal <monamagarwal...@gmail.com>
> No, I don't think this is right. __netpoll_cleanup can be called in parallel
> with bottom half access to dev->npinfo. rcu_assign pointer is safe against
> those accesses, but RCU_INIT_POINTER is not.
Hello, Neil,
But in this case, NULL is being assigned, so there should be no problem.
If this was a non-NULL pointer to a structure that had not already been
exposed to readers, then yes, this would be a problem. But NULL pointers
are OK to assign using RCU_INIT_POINTER().
Thanx, Paul
> Neil
>
> > ---
> > net/core/netpoll.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/net/core/netpoll.c b/net/core/netpoll.c
> > index 7291dde..41c4e9c 100644
> > --- a/net/core/netpoll.c
> > +++ b/net/core/netpoll.c
> > @@ -809,7 +809,7 @@ void __netpoll_cleanup(struct netpoll *np)
> > if (ops->ndo_netpoll_cleanup)
> > ops->ndo_netpoll_cleanup(np->dev);
> >
> > - rcu_assign_pointer(np->dev->npinfo, NULL);
> > + RCU_INIT_POINTER(np->dev->npinfo, NULL);
> > call_rcu_bh(&npinfo->rcu, rcu_cleanup_netpoll_info);
> > }
> > }
> > --
> > 1.7.9.5
> >
> >
> --
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