introduced lock on screen panes to prevent races

1 files changed, 101 insertions, 74 deletions

diff --git a/src/twopane.bash b/src/twopane.bash
index 1ed840b..59077fe 100755
--- a/src/twopane.bash
+++ b/src/twopane.bash
@@ -1,6 +1,6 @@
 #!/bin/bash
 BASH_ARGV0=twopane.bash
-echo -n "$0" >/proc/$$/comm
+echo -n "$0" >/proc/$BASHPID/comm
 set -e
 set -f
 set -o pipefail
@@ -8,17 +8,26 @@ shopt -s lastpipe
 
 . read_chars.bash
 
+kill_tty_forward()
+{
+        read pid < "$TWOPANE"/tty_forward.pid
+        /bin/kill "${1:-'-INT'}" -- -$pid 2>/dev/null
+}
+
 BOT_SIZE=8
 BOT_TITLE=input
 
 if [ $# = 0 ]
 then
         TOP_CMD="$SHELL -i"
-        BOT_CMD=foreground
-        #BOT_CMD=start
+        BOT_CMD=start
         #TOP_EXIT=quit
-        #TOP_EXIT=prompt
-        TOP_EXIT=restart
+        TOP_EXIT=prompt
+        #TOP_EXIT=restart
+elif [ "$TWOPANE" -a "$*" = detach ]
+then
+        kill_tty_forward -TSTP
+        exit
 else
         TOP_CMD=$*
         BOT_CMD=start
@@ -75,26 +84,41 @@ screen -ln -t "$BOT_TITLE" 0 bash --noprofile --rcfile "$TWOPANE"/bashrc -i
 layout save 0
 .
 
+with_screen_pane()
+{
+        (( $# > 1 )) || return
+        declare -i PANE="$1" LOCK
+        (( PANE > 0 )) || return
+        (
+                flock $LOCK
+                "$2" "$1" "${@:3}"
+        ) {LOCK}>"$TWOPANE"/pane$PANE
+}
+
 check_screen_pane()
 {
-        screen -p "$pane" -Q info >/dev/null
+        (( PANE > 0 )) || return
+        screen -p "$PANE" -Q info >/dev/null
 }
 
 kill_screen_pane()
 {
-        while check_screen_pane
+        (( PANE > 0 )) || return
+        while check_screen_pane "$PANE"
         do
-                screen -p "$pane" -X kill
+                screen -p "$PANE" -X kill
         done
 }
 
 start_screen_pane()
 {
-        declare -i pane="${1:-1}"
-        (( pane > 0 )) || return
-        if check_screen_pane "$pane"
+        (( PANE > 0 )) || return
+        if check_screen_pane "$PANE"
         then
+                i "pane already running: $PANE"
                 return
+        else
+                i "starting pane: $PANE"
         fi
         shift
         if [ $# = 0 ]
@@ -105,49 +129,55 @@ start_screen_pane()
         TOP_TITLE="Command: ${*@Q}"
         screen -X focus top
         screen -X screen -ln -t "$TOP_TITLE" 1 "$@"
-        start_screen_pane_subprocess "$pane"
+        start_screen_pane_subprocess
 }
 
 start_screen_pane_subprocess()
 {
-        declare -i pane="${1:-1}"
+        (( PANE > 0 )) || return
         subproc_command=(
                 exec -a top-pane-tty-forward
                         socat
                                 UNIX-LISTEN:"$TWOPANE"/socket
                                 STDIN,cfmakeraw,opost=1,onlcr=1!!STDOUT
         )
-        screen -p "$pane" -X exec .!. bash -c "${subproc_command[*]}"
+        screen -p "$PANE" -X exec .!. bash -c "${subproc_command[*]}"
 }
 
-restart_screen_pane()
+restart_pane()
 {
+        (( PANE > 0 )) || return
         kill_screen_pane
         start_screen_pane "$@"
 }
 
+restart_top_pane()
+{
+        with_screen_pane 1 restart_pane "$@"
+}
+
 connect_coproc()
 {
+        [ $# -gt 0 ] || set -- COPROC
         declare -n coproc="$1"
         shift
+        [ $# -gt 0 ] || set -- "${!coproc}"
         declare -n std1="${!coproc}_STDOUT"
         declare -n std0="${!coproc}_STDIN"
         declare -n opid="${!coproc}_PID"
-
-        if [ $# = 0 ]
-        then
-                set -- "${!coproc}"
-        fi
         if ! [ "$opid" ]
         then
+                i "coproc starting: ${!coproc}"
                 local STDERR
                 {
                         coproc "${!coproc}" \
                         {
                                 "$@"
                         } 2>&$STDERR {STDERR}>&-
+                        disown "%coproc ${!coproc} "
                 } {STDERR}>&2 2>/dev/null
-                disown
+        else
+                i "coproc already running: ${!coproc}"
         fi
         # The copied file descriptors (unlike the original coprocess
         # file descriptors, in ${coproc[0]} and ${coproc[1]}) can be
@@ -160,7 +190,7 @@ connect_coproc()
 
 disconnect_coproc()
 {
-        [ $# = 1 ] || return
+        [ $# -gt 0 ] || set -- COPROC
         declare -n coproc="$1"
         declare -n std0="${!coproc}_STDIN"
         declare -n std1="${!coproc}_STDOUT"
@@ -212,46 +242,21 @@ start()
         foreground "$@"
 }
 
-check_tty_reader()
-{
-        [ "$TTY_FORWARD_PID" ] || return
-        TTY_FORWARD_JOBSPEC=$(jobs -sl | pid_to_jobspec "$TTY_FORWARD_PID")
-        [ "$TTY_FORWARD_JOBSPEC" ]
-}
-
-pid_to_jobspec()
-{
-        while read jspec pid status cmd
-        do
-                [ "$pid" = "$1" ] || continue
-                jspec=${jspec%]*}
-                jspec=%${jspec#[}
-                echo $jspec
-                return
-        done
-        false
-}
-
 tty_forward()
 {
         printf '%d\n' "$BASHPID" > "$TWOPANE"/tty_forward.pid
         read-tty
 }
 
-kill_tty_forward()
-{
-        read pid < "$TWOPANE"/tty_forward.pid
-        /bin/kill -INT -- -$pid 2>/dev/null
-}
-
 TOP_PANE()
 {
         (exec -a bottom-pane-tty-forward socat - UNIX-CONNECT:"$TWOPANE"/socket,forever)
-        kill_tty_forward
+        x kill_tty_forward
         case "$TOP_EXIT" in
                 restart )
-                        start_screen_pane 1
-                        kill -USR1 $$
+                        # x kill -USR1 $$
+                        x kill -INT $$
+                        with_screen_pane 1 start_screen_pane "$@"
                 ;;
                 quit )
                         kill -INT $$
@@ -263,11 +268,13 @@ TOP_PANE()
         esac
 }
 
-sink()
+connect_sink()
 {
+        [ "$1" ] || return
         declare -n fd="$1"
         declare -n pid="${!fd}_PID"
         disconnect_sink "$fd"
+        i "sink starting: ${!fd}"
         exec {fd}> >("${@:2}")
         pid=$!
 }
@@ -278,6 +285,7 @@ disconnect_sink()
         declare -n fd="$1"
         [ "$fd" ] || return
         declare -n pid="${!fd}_PID"
+        i "sink stopping: ${!fd}"
         exec {fd}>&-
         kill $pid 2>/dev/null
         unset fd pid
@@ -299,30 +307,36 @@ echo_sender()
 
 background()
 {
-        start_screen_pane 1 "$@"
+        with_screen_pane 1 start_screen_pane "$@"
         focus bottom
 
         disconnect_sink ECHOSEND
         connect
-        sink ECHOSEND echo_sender
+        connect_sink ECHOSEND echo_sender
+        kill %tty_forward
+        %tty_forward &
+        disown %tty_forward
+        i 'starting tty_forward'
         quiet_bg tty_forward >&$ECHOSEND
-
-        TTY_FORWARD_PID=$!
-        printf '%d\n' "$TTY_FORWARD_PID" > "$TWOPANE"/tty_forward.pid
-        printf '%s\n' \
-                "#!/bin/bash" \
-                "kill -TSTP $TTY_FORWARD_PID" \
-                "screen -X focus bottom" \
-                > "$TWOPANE"/unforward
-        chmod +x "$TWOPANE"/unforward
+        echo $! > "$TWOPANE"/tty_forward.pid
 }
 
 foreground()
 {
-        check_tty_reader || background "$@"
-        focus top
-        fg %tty_forward >/dev/null 2>&1
-        focus bottom
+        while true
+        do
+                background "$@"
+                focus top
+                set -x
+                %tty_forward >/dev/null 2>&1
+                if [ "$TOP_EXIT" != restart ] || jobs %tty_forward >/dev/null 2>&1
+                then
+                        focus bottom
+                        set +x
+                        break
+                fi
+                set +x
+        done
 }
 
 twopane()
@@ -345,34 +359,47 @@ resize()
         screen -X resize "$@"
 }
 
+attach()
+{
+        if jobs %tty_forward >/dev/null 2>&1
+        then
+                %tty_forward
+        else
+                foreground
+        fi
+}
+
 SIGUSR1()
 {
-        i SIGUSR1 "${BASH_COMMAND@A}"
+        i "SIGUSR1: ${BASH_COMMAND@A}"
+}
+
+SIGCHLD()
+{
+        i "SIGCHILD: ${BASH_COMMAND@A}"
 }
 
 our_bashrc_main()
 {
+        BASH_ARGV0=twopane
+        echo -n "$0" >/proc/$BASHPID/comm
         set -m
         set -f
         set -o pipefail
-        trap 'quit' EXIT
         trap 'SIGUSR1' USR1
+        # trap 'SIGCHLD' CHLD
+        trap '! [ "$DEBUG" ] || read -p "Exit> "; quit' EXIT
         export PS1="$BOT_TITLE\\\$ "
 }
 
 save_file bashrc <<.
-BASH_ARGV0=twopane
-echo -n "\$0" >/proc/\$\$/comm
 ${TOP_CMD@A}
 ${BOT_CMD@A}
 ${TOP_TITLE@A}
 ${BOT_TITLE@A}
-
 ${TOP_EXIT@A}
-
 $(declare -f)
 our_bashrc_main
-
 $BOT_CMD
 .