From 3a77d81c5b30dccc3c1a97d55e00d7e853c5ddf4 Mon Sep 17 00:00:00 2001
From: Julia Vassiliki <julia.vassiliki@unsw.edu.au>
Date: Wed, 22 Apr 2026 17:29:17 +1000
Subject: [PATCH] Add improved sigint handling for cancellation

Actually propagate upwards the SIGINT as the cause
of the failure.

Signed-off-by: Julia Vassiliki <julia.vassiliki@unsw.edu.au>
---
 scripts/common  | 15 +++++++++++++++
 scripts/enqueue | 14 ++++++++++++--
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/scripts/common b/scripts/common
index 8955fcc..9049039 100755
--- a/scripts/common
+++ b/scripts/common
@@ -16,6 +16,21 @@ HOST=tftp.keg.cse.unsw.edu.au
 # Config file location
 CONFIG=~/.mq
 
+# Bash implements the "Wait and Cooperative Exit" protocol
+# If, when we receive a trap like SIGINT, we do not then exit because of a SIGINT,
+# bash assumes that we have handled SIGINT and continues as if we did not try
+# to just stop the program execution, making it look like nothing happened.
+# Hence, we must emulate this behaviour for bash to believe that we have died
+# due to the SIGINT (i.e. that after the wait() syscall, WTERMSIG(status) is SIGINT).
+# Ref: https://www.cons.org/cracauer/sigint.html
+# Ref: https://mywiki.wooledge.org/SignalTrap#Special_Note_On_SIGINT_and_SIGQUIT
+TrapExitSigInt() {
+    # Restore default handling for SIGINT
+    trap - SIGINT
+    kill -s INT $$
+}
+
+
 # Add all the other bits and pieces
 
 . "${SCRIPT_PATH}/scripts/remote"
diff --git a/scripts/enqueue b/scripts/enqueue
index 92d56d5..f162d15 100755
--- a/scripts/enqueue
+++ b/scripts/enqueue
@@ -230,7 +230,7 @@ Enqueue() {
 
         # We can setup the trap early as we check if we actually own the
         # the lock before releasing it
-        trap "UnlockSystem \"${system}\" 0 \"${key}\"; exit 1" ${SIGNALS}
+        trap "UnlockSystem \"${system}\" 0 \"${key}\"; TrapExitSigInt" ${SIGNALS}
 
         if ! LockSystem "${system}" "${retry_period}" "${total_retries}" "${key}"; then
             echo "Failed to acquire lock for system (${system})"
@@ -257,11 +257,21 @@ Enqueue() {
         # Ditto for 'bitstreamflag'
         SystemRunImage "${system}" "${completion}" "${completion_timeout}" "${errortxt}" "${logfile}" "${keep_alive}" ${linux} ${dtbflag} ${bitstreamflag} $files
         ret=$?
+
+        # Special case: SSH does not return indicating a SIGINT, so we special
+        # case instead that it returns 255 in this case.
+        # https://github.com/openssh/openssh-portable/blob/V_10_0_P1/mux.c#L2057-L2059
+        # (However, sometimes it will instead forward through status 130 from the process
+        # which received SIGINT on the other end of the SSH session. Sometimes...)
+        if [ "${ret}" == "255" ]; then
+            TrapExitSigInt
+        fi
     fi
 
     if ! ${no_lock_mods} ; then
         UnlockSystem "${system}" 0 "${key}"
-        trap "exit 1" ${SIGNALS}
+        # Reset trap behaviour to default.
+        trap - ${SIGNALS}
     fi
 
     exit $ret