On Wed, 14 Feb 2024 23:01:04 +0000, Oliver Upton <oliver.upton@xxxxxxxxx> wrote: > > On Wed, Feb 14, 2024 at 08:01:19PM +0000, Marc Zyngier wrote: > > > > Of course, we only have 3 marks, so that's a bit restrictive from a > > > > concurrency perspective, but since most callers hold a lock, it should > > > > be OK. > > > > > > They all hold *a* lock, but maybe not the same one! :) > > > > Indeed. But as long as there isn't more than 3 locks (and that the > > xarray is OK being concurrently updated with marks), we're good! > > Oh, you mean to give each existing caller their own mark? Well, each caller "class". Where "class" means "holding look 'foo'". Same lock, same mark. With a maximum of 3 (and I think we can get away with 2). > > > Maybe we should serialize the use of markers on the LPI list on the > > > config_lock. A slight misuse, but we need a mutex since we're poking at > > > guest memory. Then we can go through the whole N-dimensional locking > > > puzzle and convince ourselves it is still correct. > > > > Maybe. This thing is already seeing so many abuses that one more may > > not matter much. Need to see how it fits in the whole hierarchy of > > GIC-related locks... > > It doesn't work. We have it that the config_lock needs to be taken > outside the its_lock. > > Too many damn locks! Well, the joys of emulating highly complex HW with a braindead programming interface. I'd explore the above suggestion to avoid introducing a new lock, if at all possible. Thanks, M. -- Without deviation from the norm, progress is not possible.
