diff --git a/swh/loader/mercurial/hgutil.py b/swh/loader/mercurial/hgutil.py
--- a/swh/loader/mercurial/hgutil.py
+++ b/swh/loader/mercurial/hgutil.py
@@ -2,6 +2,7 @@
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
+
 from collections import defaultdict
 from dataclasses import dataclass
 import io
@@ -17,6 +18,8 @@
 from mercurial import bookmarks, context, error, hg, smartset, util  # type: ignore
 import mercurial.ui  # type: ignore
 
+from swh.scheduler.utils import utcnow
+
 NULLID = mercurial.node.nullid
 HgNodeId = NewType("HgNodeId", bytes)
 Repository = hg.localrepo
@@ -125,6 +128,7 @@
         errors: message queue to communicate errors
     """
     try:
+        print(f"{utcnow()} clone start")
         hg.clone(
             ui=mercurial.ui.ui.load(),
             peeropts={},
@@ -132,10 +136,12 @@
             dest=dest.encode(),
             update=False,
         )
+        print(f"{utcnow()} clone end")
     except Exception as e:
         exc_buffer = io.StringIO()
         traceback.print_exc(file=exc_buffer)
         errors.put_nowait(exc_buffer.getvalue())
+        print(f"{utcnow()} clone raise")
         raise e
 
 
@@ -147,23 +153,31 @@
         dest: clone destination
         timeout: timeout in seconds
     """
+    print(f"{utcnow()} start")
     errors: Queue = Queue()
     process = Process(target=_clone_task, args=(src, dest, errors))
+    print(f"{utcnow()} start")
     process.start()
     process.join(timeout)
+    print(f"{utcnow()} joined")
 
     if process.is_alive():
+        print(f"{utcnow()} process still alive")
         process.terminate()
-        # Give it a second (literally), then kill it
+        # Give it literally a second (in successive steps of 0.1 second), then kill it.
         # Can't use `process.join(1)` here, billiard appears to be bugged
         # https://github.com/celery/billiard/issues/270
         killed = False
+        step = 0.1
         for _ in range(10):
-            time.sleep(0.1)
+            print(f"{utcnow()} sleep {step} second")
+            time.sleep(step)
             if not process.is_alive():
+                print(f"{utcnow()} process not alive, break")
                 break
         else:
             killed = True
+            print(f"{utcnow()} process {process.pid} to stop: killed=={killed}")
             os.kill(process.pid, signal.SIGKILL)
         raise CloneTimeout(src, timeout, killed)
 
diff --git a/swh/loader/mercurial/tests/test_hgutil.py b/swh/loader/mercurial/tests/test_hgutil.py
--- a/swh/loader/mercurial/tests/test_hgutil.py
+++ b/swh/loader/mercurial/tests/test_hgutil.py
@@ -9,6 +9,8 @@
 from mercurial import hg  # type: ignore
 import pytest
 
+from swh.scheduler.utils import utcnow
+
 from .. import hgutil
 
 
@@ -16,11 +18,15 @@
     src = "https://www.mercurial-scm.org/repo/hello"
     dest = "/dev/null"
     timeout = 0.1
+    sleepy_time = 10 * timeout
+    assert sleepy_time > timeout
 
-    def clone(*args, **kwargs):
+    def clone(*args, sleepy_time=sleepy_time, **kwargs):
         # ignore SIGTERM to force sigkill
         signal.signal(signal.SIGTERM, lambda signum, frame: None)
-        time.sleep(2)
+        print(f"(false clone) {utcnow()} Sleep for {sleepy_time} seconds.")
+        time.sleep(sleepy_time)  # we make sure we exceed the timeout
+        print(f"(false clone) {utcnow()} Slept but this should never get printed!")
 
     monkeypatch.setattr(hg, "clone", clone)