* [PATCH 6/7] selftests/damon: prevent remaining cross-object state pollution
2026-08-31 14:26 [PATCH 0/7] mm/damon: misc cleanups SJ Park
2026-08-31 14:26 ` [PATCH 4/7] selftests/damon/sysfs.py: clean up sh processes used for obsolete_target test SJ Park
@ 2026-08-31 14:26 ` SJ Park
1 sibling, 0 replies; 3+ messages in thread
From: SJ Park @ 2026-08-31 14:26 UTC (permalink / raw)
To: Andrew Morton
Cc: zhaozhengzhuo, SJ Park, Shuah Khan, damon, linux-kernel,
linux-kselftest, linux-mm
From: zhaozhengzhuo <zhaozhengzhuo@uniontech.com>
_damon_sysfs.py defines constructors with mutable default arguments,
including DamosAccessPattern(), DamosQuota(), DamosWatermarks(),
DamosDests(), IntervalsGoal(), and empty lists.
Default arguments are evaluated once at function definition time.
Damos() instances created without explicit arguments therefore share
the same DamosQuota(), and the other default-constructed sub-objects
and lists are shared in the same way. The sub-objects keep
back-pointers to their owner scheme, so constructing the second Damos()
rebinds the shared quota's scheme pointer to the second object. An
item appended to one object's default contexts or filters list is also
visible from other default-constructed objects.
The shared state can corrupt test configurations. DamosQuota.sysfs_dir()
derives the sysfs directory from its scheme pointer, so operating on
the first scheme's default quota may write to the second scheme's
directory. The wrong values often match the defaults, so tests still
pass, but the behavior depends on object creation order.
Commit 8319dadcbd81 ("selftests/damon: prevent cross-context state
pollution in DamonCtx") fixed the same pattern in DamonCtx only. Fix
the remaining constructors by defaulting to None and creating fresh
objects or lists inside each constructor. Explicit arguments keep
their previous behavior.
Signed-off-by: zhaozhengzhuo <zhaozhengzhuo@uniontech.com>
Reviewed-by: SJ Park <sj@kernel.org>
Signed-off-by: SJ Park <sj@kernel.org>
---
Changes from v1
- v1: https://lore.kernel.org/38E4AAAAEDFCC283+20260827021515.1316838-1-zhaozhengzhuo@uniontech.com
- Collec R-b: from SJ.
- Rebase to latest mm-new.
tools/testing/selftests/damon/_damon_sysfs.py | 38 ++++++++++++++-----
1 file changed, 28 insertions(+), 10 deletions(-)
diff --git a/tools/testing/selftests/damon/_damon_sysfs.py b/tools/testing/selftests/damon/_damon_sysfs.py
index e6a2265d721e8..f604b7d6530b3 100644
--- a/tools/testing/selftests/damon/_damon_sysfs.py
+++ b/tools/testing/selftests/damon/_damon_sysfs.py
@@ -321,8 +321,10 @@ class DamosFilters:
filters = None
scheme = None # owner scheme
- def __init__(self, name, filters=[]):
+ def __init__(self, name, filters=None):
self.name = name
+ if filters is None:
+ filters = []
self.filters = filters
for idx, filter_ in enumerate(self.filters):
filter_.idx = idx
@@ -368,7 +370,9 @@ class DamosDests:
dests = None
scheme = None # owner scheme
- def __init__(self, dests=[]):
+ def __init__(self, dests=None):
+ if dests is None:
+ dests = []
self.dests = dests
for idx, dest in enumerate(self.dests):
dest.idx = idx
@@ -426,15 +430,21 @@ class Damos:
stats = None
tried_regions = None
- def __init__(self, action='stat', access_pattern=DamosAccessPattern(),
- quota=DamosQuota(), watermarks=DamosWatermarks(),
- core_filters=[], ops_filters=[], filters=[], target_nid=0,
- dests=DamosDests(), apply_interval_us=0):
+ def __init__(self, action='stat', access_pattern=None, quota=None,
+ watermarks=None, core_filters=None, ops_filters=None,
+ filters=None, target_nid=0, dests=None,
+ apply_interval_us=0):
self.action = action
+ if access_pattern is None:
+ access_pattern = DamosAccessPattern()
self.access_pattern = access_pattern
self.access_pattern.scheme = self
+ if quota is None:
+ quota = DamosQuota()
self.quota = quota
self.quota.scheme = self
+ if watermarks is None:
+ watermarks = DamosWatermarks()
self.watermarks = watermarks
self.watermarks.scheme = self
@@ -448,6 +458,8 @@ class Damos:
self.filters.scheme = self
self.target_nid = target_nid
+ if dests is None:
+ dests = DamosDests()
self.dests = dests
self.dests.scheme = self
@@ -568,10 +580,12 @@ class DamonAttrs:
context = None
def __init__(self, sample_us=5000, aggr_us=100000,
- intervals_goal=IntervalsGoal(), update_us=1000000,
- min_nr_regions=10, max_nr_regions=1000):
+ intervals_goal=None, update_us=1000000, min_nr_regions=10,
+ max_nr_regions=1000):
self.sample_us = sample_us
self.aggr_us = aggr_us
+ if intervals_goal is None:
+ intervals_goal = IntervalsGoal()
self.intervals_goal = intervals_goal
self.intervals_goal.attrs = self
self.update_us = update_us
@@ -703,7 +717,9 @@ class Kdamond:
idx = None # index of this kdamond between siblings
kdamonds = None # parent
- def __init__(self, contexts=[], refresh_ms=None):
+ def __init__(self, contexts=None, refresh_ms=None):
+ if contexts is None:
+ contexts = []
self.contexts = contexts
self.refresh_ms = refresh_ms
for idx, context in enumerate(self.contexts):
@@ -853,7 +869,9 @@ class Kdamond:
class Kdamonds:
kdamonds = []
- def __init__(self, kdamonds=[]):
+ def __init__(self, kdamonds=None):
+ if kdamonds is None:
+ kdamonds = []
self.kdamonds = kdamonds
for idx, kdamond in enumerate(self.kdamonds):
kdamond.idx = idx
--
2.47.3
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