On Mon, 26 Jan 2026 at 22:36, Peter Zijlstra <[email protected]> wrote: > > On Mon, Jan 26, 2026 at 10:54:56AM -0800, Bart Van Assche wrote: > > > Has it ever been considered to add support in the clang compiler for a > > variant of __must_hold() that expresses that one of two capabilities > > must be held by the caller? I think that would remove the need to > > annotate SRCU update-side code with __acquire_shared(ssp) and > > __release_shared(ssp). > > Right, I think I've asked for logical operators like that. Although I > think it was in the __guarded_by() clause rather than the __must_hold(). > Both || and && would be nice to have ;-)
Some attributes take multiple arguments (__must_hold does), though __guarded_by doesn't. Yet, && can still be had with adding it multiple times e.g. '__guarded_by(pi_lock) __guarded_by(rq->__lock)'. Only thing that doesn't exist is ||. I think the syntax you ask for won't fly, but I can add it to the backlog to investigate an _any variant of these attributes. Don't hold your breath though, given the time it takes to land all that in a released Clang version. > Specifically, I think I asked for something like: > > cpumask_t cpus_allowed __guarded_by(pi_lock && rq->__lock) > __guarded_shared_by(pi_lock || > rq->__lock); > > > I think Marco's suggestion was to use 'fake' locks to mimic those > semantics.
