From: Paul Hänsch Date: Mon, 23 Aug 2021 15:29:30 +0000 (+0200) Subject: simpler lock algorithm using files X-Git-Url: http://git.plutz.net/?a=commitdiff_plain;h=07b4b96f662c7649130701b27865a851488ee2f7;hp=38702dbb48387609925572f2269b222f87eb9c1a;p=cgilite simpler lock algorithm using files --- diff --git a/storage.sh b/storage.sh index 61eec88..77ee29c 100755 --- a/storage.sh +++ b/storage.sh @@ -1,6 +1,6 @@ #!/bin/sh -# Copyright 2018, 2019 Paul Hänsch +# Copyright 2018, 2019, 2021 Paul Hänsch # # This is a file format helper, part of CGIlite. # @@ -25,41 +25,40 @@ BR=' ' LOCK(){ - local lock timeout block - lock="${1}.lock" - timeout="${2-20}" - if [ \! -w "${lock%/*}" ] || [ -e "$lock" -a \! -d "$lock" ]; then + local lock="${1}.lock" timeout="${2-20}" block + + if [ \! -w "${lock%/*}" ] || [ -e "$lock" -a \! -f "$lock" ]; then debug "Impossible to get lock: $lock" return 1 fi - while ! mkdir "$lock" 2>&-; do - block="$(cat "$lock/pid" || printf 1)" - if ! { ps -eo pid |grep -qwF "$block"; }; then - debug "Overriding stale lock: $lock" - break - fi - if [ $timeout -le 0 ]; then - debug "Timeout while trying to get lock: $lock" - return 1 + while [ $timeout -gt 0 ]; do + printf '%i\n' $$ >>"${lock}" + read block <"$lock" + if [ "$block" = $$ ]; then + return 0 + elif ! { ps -eo pid |grep -qwF "$block"; }; then + debug "Trying to override stale lock: $lock" + if LOCK "$lock" 1; then + rm -- "$lock" + RELEASE "$lock" + fi + else + timeout=$((timeout - 1)) + [ $timeout -gt 0 ] && sleep 1 fi - timeout=$((timeout - 1)) - sleep 1 done - printf '%i\n' $$ >"${lock}/pid" - return 0 + + debug "Timeout while trying to get lock: $lock" + return 1 } RELEASE(){ - local lock - lock="${1}.lock" - if [ "$(cat "$lock/pid")" = "$$" ]; then - rm "$lock/pid" - if ! rmdir "$lock"; then - debug "Cannot remove tainted lock: $lock" - printf '%i\n' $$ >"${lock}/pid" - return 1 - fi + local lock="${1}.lock" block + + read block <"$lock" + if [ "$block" = $$ ]; then + rm -- "$lock" return 0 else debug "Refusing to release foreign lock: $lock"