NOTES: Killing stray 'rsession' processes might require SIGKILL

[HenrikBengtsson]

A user had stray rsession processes. Using:

pkill rsession

was not sufficient to terminate those. They had to use:

pkill -SIGKILL rsession

to get rid of them.

[HenrikBengtsson]

FWIW, terminate_pid() tries with 4 x SIGTERM, then SIGKILL;

rstudio-server-controller/bin/rsc

Lines 864 to 883 in b5df9ba

	if [[ ${#signals[@]} -eq 0 ]]; then
	signals=("SIGTERM" "SIGTERM" "SIGTERM" "SIGTERM" "SIGKILL")
	fi
	mdebug " - pid: ${pid} (before check)"
	mdebug " - signals: [n=${#signals[@]}] ${signals[*]}"
	pid=$(check_pid "${pid}")
	for kk in $(seq ${#signals[@]}); do
	if [[ ${pid} -eq 0 ]]; then
	break
	fi
	signal=${signals[$((kk - 1))]}
	mdebug "Attempt ${kk}: kill -${signal} ${pid}"
	kill "-${signal}" "${pid}" && mdebug "Sending ${signal} to PID ${pid}"
	sleep 1.0
	pid=$(check_pid "${pid}")
	if [[ ${pid} -ne 0 ]]; then
	warn "Failed to terminate process (PID ${pid}). Will try again in three seconds"
	sleep 2.0
	fi
	done