Messages in this thread | | | Date | Wed, 9 Oct 2013 15:26:56 -0700 | From | Josh Triplett <> | Subject | Re: [PATCH v2 tip/core/rcu 01/13] rcu: Make rcu_assign_pointer's assignment volatile and type-safe |
| |
On Wed, Oct 09, 2013 at 02:29:34PM -0700, Paul E. McKenney wrote: > From: Josh Triplett <josh@joshtriplett.org> > > rcu_assign_pointer needs to use ACCESS_ONCE to make the assignment to > the destination pointer volatile, to protect against compilers too > clever for their own good. > > In addition, since rcu_assign_pointer force-casts the source pointer to > add the __rcu address space (overriding any existing address space), add > an explicit check that the source pointer has the __kernel address space > to start with. > > This new check produces warnings like this, when attempting to assign > from a __user pointer: > > test.c:25:9: warning: incorrect type in argument 2 (different address spaces) > test.c:25:9: expected struct foo *<noident> > test.c:25:9: got struct foo [noderef] <asn:1>*badsrc > > Signed-off-by: Josh Triplett <josh@joshtriplett.org> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
See my responses to the cover letter; I'd suggest making this the last patch of the series to avoid introducing and subsequently fixing warnings.
I'd suggest adding the comment I mentioned in my second response as the new first patch of the series, since it applies to the old version as well; thus, the series would first add the comment documenting the evaluate-once constraint, then add all the calls to rcu_access_pointer, and finally add this patch introducing the sparse checking.
- Josh Triplett
| |