selftests/damon: prevent cross-context state pollution in DamonCtx

Patch series "selftests/damon: misc fixes for test bugs", v3.

This series fixes several bugs in the DAMON selftests.  Most are trivial
but makes test output wrong or even silently pass the one test case for
'avail_operation' file existence check.

Patch 1 fixes mutable default arguments in DamonCtx.__init__() that cause
state to leak between test instances.

Patch 2 fixes wrong operator precedence and join TypeError in
damos_tried_regions.py.

Patch 3 fixes several wrong strings that produce dead elif branches,
skipped file existence checks, and broken dict key lookups.


This patch (of 3):

DamonCtx.__init__() uses mutable default values for monitoring_attrs,
targets, and schemes.  In Python these are evaluated once at function
definition time, so multiple DamonCtx instances can unintentionally share
the same lists and DamonAttrs instance.

Replace the mutable defaults with None sentinels and initialize the
objects when needed.

Link: https://lore.kernel.org/20260629144648.134092-1-sj@kernel.org
Link: https://lore.kernel.org/20260601032314.424013-2-kunwu.chan@linux.dev
Link: https://lore.kernel.org/20260629144648.134092-2-sj@kernel.org
Co-developed-by: Wang Lian <lianux.mm@gmail.com>
Signed-off-by: Wang Lian <lianux.mm@gmail.com>
Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
Signed-off-by: SJ Park <sj@kernel.org>
Reviewed-by: SJ Park <sj@kernel.org>
Cc: Kunwu Chan <chentao@kylinos.cn>
Cc: Wang Lian <lianux.mm@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/tools/testing/selftests/damon/_damon_sysfs.py b/tools/testing/selftests/damon/_damon_sysfs.py
index 8b12cc048440..2f6f2699db25 100644
--- a/tools/testing/selftests/damon/_damon_sysfs.py
+++ b/tools/testing/selftests/damon/_damon_sysfs.py
@@ -624,17 +624,23 @@ class DamonCtx:
     pause = None
     idx = None
 
-    def __init__(self, ops='paddr', monitoring_attrs=DamonAttrs(), targets=[],
-            schemes=[], pause=False):
+    def __init__(self, ops='paddr', monitoring_attrs=None, targets=None,
+            schemes=None, pause=False):
         self.ops = ops
+        if monitoring_attrs is None:
+            monitoring_attrs = DamonAttrs()
         self.monitoring_attrs = monitoring_attrs
         self.monitoring_attrs.context = self
 
+        if targets is None:
+            targets = []
         self.targets = targets
         for idx, target in enumerate(self.targets):
             target.idx = idx
             target.context = self
 
+        if schemes is None:
+            schemes = []
         self.schemes = schemes
         for idx, scheme in enumerate(self.schemes):
             scheme.idx = idx