Re: [PATCH 01/18] drivers core: Add I/O ASID allocator

Paul E. McKenney
2019-04-09T23:17:27Z

On Tue, Apr 09, 2019 at 06:21:30PM +0300, Andriy Shevchenko wrote:
> On Tue, Apr 09, 2019 at 07:53:08AM -0700, Paul E. McKenney wrote:
> > On Tue, Apr 09, 2019 at 01:30:30PM +0300, Andriy Shevchenko wrote:
> > > On Tue, Apr 09, 2019 at 03:04:36AM -0700, Christoph Hellwig wrote:
> > > > On Tue, Apr 09, 2019 at 01:00:49PM +0300, Andriy Shevchenko wrote:
> > > > > I think it makes sense to add a helper macro to rcupdate.h
> > > > > (and we have several cases in kernel that can utilize it)
> > > > >
> > > > > #define kfree_non_null_rcu(ptr, rcu_head) \
> > > > > do { \
> > > > > if (ptr) \
> > > > > kfree_rcu(ptr, rcu_head); \
> > > > > } while (0)
> > > > >
> > > > > as a more common pattern for resource deallocators.
> > > >
> > > > I think that should move straight into kfree_rcu.
> > >
> > > Possible. I didn't dare to offer this due to lack of knowledge how it's used in
> > > other places.
> > >
> > > > In general
> > > > we expect *free* to deal with NULL pointers transparently, so we
> > > > should do so here as well.
> > >
> > > Exactly my point, thanks.
> >
> > As shown below?
>
> Looks pretty much good to me, thanks!
> Reviewed-by: Andriy Shevchenko <andriy.shevchenko@linux.intel.com>

Applied, thank you!

Thanx, Paul

> > And now that you mention it, it is a bit surprising that no one has
> > complained before. ;-)
> >
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > commit 23ad938244968e9d2a8001a1c52887c113b182f6
> > Author: Paul E. McKenney <paulmck@linux.ibm.com>
> > Date: Tue Apr 9 07:48:18 2019 -0700
> >
> > rcu: Make kfree_rcu() ignore NULL pointers
> >
> > This commit makes the kfree_rcu() macro's semantics be consistent
> > with the likes of kfree() by adding a check for NULL pointers, so
> > that kfree_rcu(NULL, ...) is a no-op.
> >
> > Reported-by: Andriy Shevchenko <andriy.shevchenko@linux.intel.com>
> > Reported-by: Christoph Hellwig <hch@infradead.org>
> > Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
> >
> > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> > index 922bb6848813..c68649b9bcec 100644
> > --- a/include/linux/rcupdate.h
> > +++ b/include/linux/rcupdate.h
> > @@ -828,9 +828,13 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
> > * The BUILD_BUG_ON check must not involve any function calls, hence the
> > * checks are done in macros here.
> > */
> > -#define kfree_rcu(ptr, rcu_head) \
> > - __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
> > -
> > +#define kfree_rcu(ptr, rhf) \
> > +do { \
> > + typeof (ptr) ___p = (ptr); \
> > + \
> > + if (___p) \
> > + __kfree_rcu(&((___p)->rhf), offsetof(typeof(*(ptr)), rhf)); \
> > +} while (0)
> >
> > /*
> > * Place this after a lock-acquisition primitive to guarantee that
> >
>
> --
> With Best Regards,
> Andy Shevchenko