On Thu, 11 Dec 2025 at 13:26, Peter Zijlstra <[email protected]> wrote: > > On Thu, Nov 20, 2025 at 04:09:41PM +0100, Marco Elver wrote: > > Mark functions that conditionally acquire the passed lock. > > > > Signed-off-by: Marco Elver <[email protected]> > > --- > > include/linux/kref.h | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/include/linux/kref.h b/include/linux/kref.h > > index 88e82ab1367c..9bc6abe57572 100644 > > --- a/include/linux/kref.h > > +++ b/include/linux/kref.h > > @@ -81,6 +81,7 @@ static inline int kref_put(struct kref *kref, void > > (*release)(struct kref *kref) > > static inline int kref_put_mutex(struct kref *kref, > > void (*release)(struct kref *kref), > > struct mutex *mutex) > > + __cond_acquires(true, mutex) > > { > > if (refcount_dec_and_mutex_lock(&kref->refcount, mutex)) { > > release(kref); > > @@ -102,6 +103,7 @@ static inline int kref_put_mutex(struct kref *kref, > > static inline int kref_put_lock(struct kref *kref, > > void (*release)(struct kref *kref), > > spinlock_t *lock) > > + __cond_acquires(true, lock) > > { > > if (refcount_dec_and_lock(&kref->refcount, lock)) { > > release(kref); > > -- > > 2.52.0.rc1.455.g30608eb744-goog > > > > Note that both use the underlying refcount_dec_and_*lock() functions. > Its a bit sad that annotation those isn't sufficient. These are inline > functions after all, the compiler should be able to see through all that.
Wrappers will need their own annotations; for this kind of static analysis (built-in warning diagnostic), inferring things like __cond_acquires(true, lock) is far too complex (requires intra-procedural control-flow analysis), and would likely be incomplete too. It might also be reasonable to argue that the explicit annotation is good for documentation. Aside: There's other static analysis tooling, like clang-analyzer that can afford to do more complex flow-sensitive intra-procedural analysis. But that has its own limitations, requires separate invocation, and is pretty slow in comparison.
