contest: vm: kmemleak: eat, sleep, rave, repeat

As recommended by Catalin (and Fatboy Slim???), it seems better to scan,
wait for the grace period, scan again, then look for leaks. This should
catch most issues, and avoid most of the false positives.

Link: https://lore.kernel.org/[email protected]
Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>

Author: matttbe

contest/remote/lib/vm.py

@@ -405,12 +405,13 @@ def check_health(self):
         if self.fail_state:
             return
         if self.has_kmemleak:
+            # First scan, to identify possible leaks
+            self.cmd("echo scan > /sys/kernel/debug/kmemleak")
+            self.drain_to_prompt()
             # kmemleak needs objects to be at least MSECS_MIN_AGE (5000)
             # before it considers them to have been leaked
             sleep(5)
-            self.cmd("echo scan > /sys/kernel/debug/kmemleak && cat /sys/kernel/debug/kmemleak")
-            self.drain_to_prompt()
-            # Do it twice, kmemleak likes to hide the leak on the first attempt
+            # Second scan, to identify what has really leaked
             self.cmd("echo scan > /sys/kernel/debug/kmemleak && cat /sys/kernel/debug/kmemleak")
             self.drain_to_prompt()