diff --git a/spec_15.rst b/spec_15.rst
index 2f41599..8d944b8 100644
--- a/spec_15.rst
+++ b/spec_15.rst
@@ -389,8 +389,10 @@ to do so, the IMP SHALL handle SIGUSR1 as a surrogate for SIGKILL.  Upon
 receipt of this signal, the IMP SHOULD deliver SIGKILL to all processes in
 the job's container, including the job shell.
 
-The mechanism by which processes are identified to receive SIGKILL is
-outside the scope of this document.
+The IMP shall get the basename of the current cgroup directory at startup.
+If the directory begins with "imp-shell", then the IMP SHALL deliver SIGKILL
+to all PIDs listed in cgroup.procs. Otherwise, the IMP SHALL deliver SIGKILL
+only to its direct child and optionally MAY include descendants.
 
 IMP configuration
 =================
diff --git a/spell.en.pws b/spell.en.pws
index 26b80fe..8437516 100644
--- a/spell.en.pws
+++ b/spell.en.pws
@@ -492,3 +492,5 @@ DoS
 lookups
 chu
 unsatisfiable
+cgroup
+procs