The `BasePrefetcher` python class had members `_events` and `_tlbs` defined as lists, meaning that any call to `list.append` on them would affect `_events` and `_tlbs` for all prefetchers, not just the calling object. This change redefines them as instance members to fix the problem. Change-Id: I68feb1d6d78e2fa5e8775afba8c81c6dd0de6c60 Signed-off-by: Isaac Sánchez Barrera <isaac.sanchez@bsc.es> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/32394 Maintainer: Jason Lowe-Power <power.jg@gmail.com> Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Jason Lowe-Power <power.jg@gmail.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>