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? 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 <paul...@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.shevche...@linux.intel.com> Reported-by: Christoph Hellwig <h...@infradead.org> Signed-off-by: Paul E. McKenney <paul...@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 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu