Merge pull request #61 from v9v/fix-autosave-race

Fix race condition in autosave

Author: bruno-

scripts/continuum_save.sh

@@ -34,8 +34,26 @@ fetch_and_run_tmux_resurrect_save_script() {
 	fi
 }
 
+acquire_lock() {
+	# Sometimes tmux starts multiple saves in parallel. We want only one
+	# save to be running, otherwise we can get corrupted saved state.
+	local lockdir_prefix="/tmp/tmux-continuum-$(current_tmux_server_pid)-lock-"
+	# The following implements a lock that auto-expires after 100...200s.
+	local lock_generation=$((`date +%s` / 100))
+	local lockdir1="${lockdir_prefix}${lock_generation}"
+	local lockdir2="${lockdir_prefix}$(($lock_generation + 1))"
+	if mkdir "$lockdir1"; then
+		trap "rmdir "$lockdir1"" EXIT
+		if mkdir "$lockdir2"; then
+			trap "rmdir "$lockdir1" "$lockdir2"" EXIT
+			return 0
+		fi
+	fi
+	return 1  # Someone else has the lock.
+}
+
 main() {
-	if supported_tmux_version_ok && auto_save_not_disabled && enough_time_since_last_run_passed; then
+	if supported_tmux_version_ok && auto_save_not_disabled && enough_time_since_last_run_passed && acquire_lock; then
 		fetch_and_run_tmux_resurrect_save_script
 	fi
 }