selftests/damon/sysfs.py: stop DAMON for dumping failures

Commit 4ece01897627 ("selftests/damon: add python and drgn-based DAMON
sysfs test") in mm-stable tree introduced sysfs.py that runs drgn for
dumping DAMON status.  When the DAMON status dumping fails for reasons
including drgn uninstalled environment, the test fails without stopping
DAMON.  Following DAMON selftests that assumes DAMON is not running when
they executed therefore fail.  Catch dumping failures and stop DAMON for
that case.

Link: https://lkml.kernel.org/r/20250722060330.56068-1-sj@kernel.org
Fixes: 4ece01897627 ("selftests/damon: add python and drgn-based DAMON sysfs test")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202507220707.9c5d6247-lkp@intel.com
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/damon/sysfs.py b/tools/testing/selftests/damon/sysfs.py
index e67008fd055dfe330b886a535e84719258877aea..fdc04f12be547097dce694eb98f50337b43f017d 100755 (executable)
--- a/tools/testing/selftests/damon/sysfs.py
+++ b/tools/testing/selftests/damon/sysfs.py
@@ -8,6 +8,10 @@ import subprocess
 import _damon_sysfs
 
 def dump_damon_status_dict(pid):
+    try:
+        subprocess.check_output(['which', 'drgn'], stderr=subprocess.DEVNULL)
+    except:
+        return None, 'drgn not found'
     file_dir = os.path.dirname(os.path.abspath(__file__))
     dump_script = os.path.join(file_dir, 'drgn_dump_damon_status.py')
     rc = subprocess.call(['drgn', dump_script, pid, 'damon_dump_output'],
@@ -40,6 +44,7 @@ def main():
     status, err = dump_damon_status_dict(kdamonds.kdamonds[0].pid)
     if err is not None:
         print(err)
+        kdamonds.stop()
         exit(1)
 
     if len(status['contexts']) != 1: