Merge branch 'darktohka/dblock' into 'master'

Ignore database locks if the process that locked the database no longer exists

See merge request pacman/pacman!231

lib/libalpm/handle.c

@@ -21,6 +21,7 @@
  */
 
 #include <errno.h>
+#include <signal.h>
 #include <stdlib.h>
 #include <string.h>
 #include <limits.h>
@@ -135,10 +136,59 @@ int _alpm_handle_lock(alpm_handle_t *handle)
 	FREE(dir);
 
 	do {
-		handle->lockfd = open(handle->lockfile, O_WRONLY | O_CREAT | O_EXCL | O_CLOEXEC, 0000);
+		handle->lockfd = open(handle->lockfile, O_RDWR | O_CREAT | O_CLOEXEC, 0000);
 	} while(handle->lockfd == -1 && errno == EINTR);
 
-	return (handle->lockfd >= 0 ? 0 : -1);
+	if(handle->lockfd < 0) {
+		/* failed to open lock for writing */
+		return -1;
+	}
+
+	/* lock opened */
+	/* check the pid */
+	pid_t pid = getpid();
+	char buf[12];
+	ssize_t bytesread = read(handle->lockfd, buf, sizeof(buf) - 1);
+
+	buf[bytesread] = '\0';
+	pid_t lockedpid;
+
+	if(sscanf(buf, "%d", &lockedpid) == 1 && kill(lockedpid, 0) == 0 && errno != ESRCH) {
+		/* could not grab lock */
+		/* old pid is still active */
+		close(handle->lockfd);
+		handle->lockfd = -1;
+		return -1;
+	}
+
+	/* write pid to lock */
+	/* first allocate string for pid */
+	char *pidstr = NULL;
+	int len = asprintf(&pidstr, "%d\n", pid);
+
+	if(len == -1) {
+		_alpm_log(handle, ALPM_LOG_ERROR, "alloc failure: could not allocate pid");
+		close(handle->lockfd);
+		unlink(handle->lockfile);
+		handle->lockfd = -1;
+		return -1;
+	}
+
+	/* finally write pid to lock */
+	int writtenbytes = write(handle->lockfd, pidstr, len);
+
+	/* cleanup */
+	FREE(pidstr);
+
+	if(writtenbytes != len) {
+		_alpm_log(handle, ALPM_LOG_ERROR, "could not write pid to lockfile");
+		close(handle->lockfd);
+		unlink(handle->lockfile);
+		handle->lockfd = -1;
+		return -1;
+	}
+
+	return 0;
 }
 
 int SYMEXPORT alpm_unlock(alpm_handle_t *handle)

scripts/libmakepkg/util/lock.sh.in

@@ -0,0 +1,31 @@
+#!/bin/bash
+#
+#   lock.sh - functions to handle pacman locking
+#
+#   Copyright (c) 2024 Pacman Development Team <pacman-dev@lists.archlinux.org>
+#
+#   This program is free software; you can redistribute it and/or modify
+#   it under the terms of the GNU General Public License as published by
+#   the Free Software Foundation; either version 2 of the License, or
+#   (at your option) any later version.
+#
+#   This program is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#   GNU General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+is_pacman_locked() {
+	local lockfile="$(pacman-conf DBPath)/db.lck"
+	if [[ -f $lockfile ]]; then
+		local pid=$(<"$lockfile")
+		# Check if the pid is valid and the process is still running
+		if [[ -n $pid && $pid =~ ^[0-9]+$ && -d /proc/$pid ]]; then
+			return 0
+		fi
+	fi
+	return 1
+}

scripts/libmakepkg/util/meson.build

@@ -5,6 +5,7 @@ sources = [
   'config.sh.in',
   'dirsize.sh.in',
   'error.sh.in',
+  'lock.sh.in',
   'message.sh.in',
   'option.sh.in',
   'parseopts.sh.in',

scripts/makepkg.sh.in

@@ -243,15 +243,12 @@ run_pacman() {
 		else
 			cmd=(su root -c "$cmdescape")
 		fi
-		local lockfile="$(pacman-conf DBPath)/db.lck"
-		while [[ -f $lockfile ]]; do
 		local timer=0
-			msg "$(gettext "Pacman is currently in use, please wait...")"
+		while is_pacman_locked && (( timer < 10 )); do
-			while [[ -f $lockfile ]] && (( timer < 10 )); do
 			(( ++timer ))
+			msg "$(gettext "Pacman is currently in use, please wait...")"
 			sleep 3
 		done
-		done
 	fi
 	"${cmd[@]}"
 }

scripts/pacman-db-upgrade.sh.in

@@ -30,6 +30,7 @@ declare -r myver='@PACKAGE_VERSION@'
 MAKEPKG_LIBRARY=${MAKEPKG_LIBRARY:-'@libmakepkgdir@'}
 
 # Import libmakepkg
+source "$MAKEPKG_LIBRARY"/util/lock.sh
 source "$MAKEPKG_LIBRARY"/util/message.sh
 source "$MAKEPKG_LIBRARY"/util/parseopts.sh
 
@@ -132,15 +133,18 @@ fi
 
 # strip any trailing slash from our dbroot
 dbroot="${dbroot%/}"
+
+# make sure pacman isn't running
+if is_pacman_locked; then
+	die "$(gettext "Pacman lock file was found. Cannot run while pacman is running.")"
+fi
+
 # form the path to our lockfile location
 lockfile="${dbroot}/db.lck"
 
-# make sure pacman isn't running
-if [[ -f $lockfile ]]; then
-	die "$(gettext "Pacman lock file was found. Cannot run while pacman is running.")"
-fi
 # do not let pacman run while we do this
-touch "$lockfile"
+# write our pid to the lockfile
+echo $$ > "$lockfile"
 
 if [[ -f "${dbroot}"/local/ALPM_DB_VERSION ]]; then
 	db_version=$(cat "${dbroot}"/local/ALPM_DB_VERSION)

test/pacman/pmtest.py

@@ -232,7 +232,7 @@ class pmtest(object):
         return files
 
     def run(self, pacman):
-        if os.path.isfile(util.PM_LOCK):
+        if util.ispacmanlocked():
             tap.bail("\tERROR: another pacman session is on-going -- skipping")
             return
 

test/pacman/util.py

@@ -184,3 +184,15 @@ def mkdir(path):
     elif os.path.isfile(path):
         raise OSError("'%s' already exists and is not a directory" % path)
     os.makedirs(path, 0o755)
+
+#
+# Locking
+#
+def ispacmanlocked():
+    if not os.path.exists(PM_LOCK):
+        return False
+
+    with open(PM_LOCK, 'r') as f:
+        pid = f.read().strip()
+
+    return pid.isdigit() and os.path.exists(f'/proc/{pid}')