On Mon, Jan 19, 2026 at 09:45:48AM -0500, Joel Fernandes wrote: > On Sun, Jan 19, 2026 at 03:11:18PM +0100, Peter Zijlstra wrote: > > By holding an extra rcu_sync reference, the percpu rwsem is kept into > > the the slow path, avoiding the rcu-sync on down_write(), which was very > > prevalent per this: > > > > https://lkml.kernel.org/r/[email protected] > > Makes sense, though I wonder if we should have a separate percpu-rwsem API > for this rather than directly accessing the lock-internal rcu_sync state? > Other future percpu_rw_semaphore users may benefit as well.
Yeah, perhaps. There is one other user, the above makes two. kernel/cgroup/cgroup.c: rcu_sync_enter(&cgroup_threadgroup_rwsem.rss);
