On Thu, Aug 15, 2013 at 12:03:33AM +0200, Mattias Andrée wrote:
> This allows for further improvement of pacman where shared locks
> could also be used, in cases there pacman only reads the database
> and does not edit it.
>
> File locks also makes it easy to let pacman wait until the
> block instance has finished, by just not using the LOCK_NB flag.
> ---
And the question that comes up every time this patch arises: what about
NFS?
No, we won't change this.
> lib/libalpm/be_sync.c | 5 +----
> lib/libalpm/handle.c | 26 ++++++++++++++------------
> lib/libalpm/handle.h | 2 +-
> lib/libalpm/trans.c | 7 +------
> scripts/pacman-db-upgrade.sh.in | 9 +++++----
> scripts/pacman-optimize.sh.in | 9 +++++----
> 6 files changed, 27 insertions(+), 31 deletions(-)
>
> diff --git a/lib/libalpm/be_sync.c b/lib/libalpm/be_sync.c
> index 0b99684..e7c8c4b 100644
> --- a/lib/libalpm/be_sync.c
> +++ b/lib/libalpm/be_sync.c
> @@ -284,10 +284,7 @@ int SYMEXPORT alpm_db_update(int force, alpm_db_t *db)
>
> cleanup:
>
> - if(_alpm_handle_unlock(handle)) {
> - _alpm_log(handle, ALPM_LOG_WARNING, _("could not remove lock
> file %s\n"),
> - handle->lockfile);
> - }
> + _alpm_handle_unlock(handle);
> free(syncpath);
> umask(oldmask);
> return ret;
> diff --git a/lib/libalpm/handle.c b/lib/libalpm/handle.c
> index 53c86c5..5d1cfb7 100644
> --- a/lib/libalpm/handle.c
> +++ b/lib/libalpm/handle.c
> @@ -27,6 +27,7 @@
> #include <sys/types.h>
> #include <syslog.h>
> #include <sys/stat.h>
> +#include <sys/file.h>
> #include <fcntl.h>
>
> /* libalpm */
> @@ -44,6 +45,7 @@ alpm_handle_t *_alpm_handle_new(void)
>
> CALLOC(handle, 1, sizeof(alpm_handle_t), return NULL);
> handle->deltaratio = 0.0;
> + handle->lckstream = -1;
>
> return handle;
> }
> @@ -95,7 +97,7 @@ int _alpm_handle_lock(alpm_handle_t *handle)
> char *dir, *ptr;
>
> ASSERT(handle->lockfile != NULL, return -1);
> - ASSERT(handle->lckstream == NULL, return 0);
> + ASSERT(handle->lckstream < 0, return 0);
>
> /* create the dir of the lockfile first */
> dir = strdup(handle->lockfile);
> @@ -110,14 +112,14 @@ int _alpm_handle_lock(alpm_handle_t *handle)
> FREE(dir);
>
> do {
> - fd = open(handle->lockfile, O_WRONLY | O_CREAT | O_EXCL, 0000);
> + fd = open(handle->lockfile, O_WRONLY | O_CREAT);
> } while(fd == -1 && errno == EINTR);
> if(fd >= 0) {
> - FILE *f = fdopen(fd, "w");
> - fprintf(f, "%ld\n", (long)getpid());
> - fflush(f);
> fsync(fd);
> - handle->lckstream = f;
> + if(flock(fd, LOCK_EX | LOCK_NB) < 0) {
> + return -1;
> + }
> + handle->lckstream = fd;
> return 0;
> }
> return -1;
> @@ -127,14 +129,14 @@ int _alpm_handle_lock(alpm_handle_t *handle)
> int _alpm_handle_unlock(alpm_handle_t *handle)
> {
> ASSERT(handle->lockfile != NULL, return -1);
> - ASSERT(handle->lckstream != NULL, return 0);
> -
> - fclose(handle->lckstream);
> - handle->lckstream = NULL;
> + ASSERT(handle->lckstream >= 0, return 0);
>
> - if(unlink(handle->lockfile) && errno != ENOENT) {
> - return -1;
> + flock(handle->lckstream, LOCK_UN);
> + if(flock(handle->lckstream, LOCK_EX | LOCK_NB) == 0) {
> + unlink(handle->lockfile);
> + flock(handle->lckstream, LOCK_UN);
> }
> + handle->lckstream = NULL;
> return 0;
> }
>
> diff --git a/lib/libalpm/handle.h b/lib/libalpm/handle.h
> index 5e84d58..7ca90ff 100644
> --- a/lib/libalpm/handle.h
> +++ b/lib/libalpm/handle.h
> @@ -55,7 +55,7 @@ struct __alpm_handle_t {
> alpm_db_t *db_local; /* local db pointer */
> alpm_list_t *dbs_sync; /* List of (alpm_db_t *) */
> FILE *logstream; /* log file stream pointer */
> - FILE *lckstream; /* lock file stream pointer if one exists */
> + int lckstream; /* lock file file descriptor if one exists */
> alpm_trans_t *trans;
>
> #ifdef HAVE_LIBCURL
> diff --git a/lib/libalpm/trans.c b/lib/libalpm/trans.c
> index 8d4e0e7..122f35b 100644
> --- a/lib/libalpm/trans.c
> +++ b/lib/libalpm/trans.c
> @@ -215,12 +215,7 @@ int SYMEXPORT alpm_trans_release(alpm_handle_t *handle)
>
> /* unlock db */
> if(!nolock_flag) {
> - if(_alpm_handle_unlock(handle)) {
> - _alpm_log(handle, ALPM_LOG_WARNING, _("could not remove
> lock file %s\n"),
> - handle->lockfile);
> - alpm_logaction(handle, ALPM_CALLER_PREFIX,
> - "warning: could not remove lock file %s\n",
> handle->lockfile);
> - }
> + _alpm_handle_unlock(handle);
> }
>
> return 0;
> diff --git a/scripts/pacman-db-upgrade.sh.in b/scripts/pacman-db-upgrade.sh.in
> index a1630c5..20cf035 100644
> --- a/scripts/pacman-db-upgrade.sh.in
> +++ b/scripts/pacman-db-upgrade.sh.in
> @@ -102,12 +102,12 @@ dbroot="${dbroot%/}"
> # form the path to our lockfile location
> lockfile="${dbroot}/db.lck"
>
> -# make sure pacman isn't running
> -if [[ -f $lockfile ]]; then
> +# make sure pacman isn't running and stop other instances for starting
> +exec 100<>"$lockfile"
> +if ! flock -x --nonblock 100; then
> + flock --close 100
> 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"
>
> # pacman-3.4 to 3.5 upgrade - merge depends into desc
> if [[ $(find "$dbroot"/local -name depends) ]]; then
> @@ -123,5 +123,6 @@ fi
>
> # remove the lock file
> rm -f "$lockfile"
> +flock --close 100
>
> # vim: set ts=2 sw=2 noet:
> diff --git a/scripts/pacman-optimize.sh.in b/scripts/pacman-optimize.sh.in
> index 47fbb49..8c6e556 100644
> --- a/scripts/pacman-optimize.sh.in
> +++ b/scripts/pacman-optimize.sh.in
> @@ -114,12 +114,12 @@ dbroot="${dbroot%/}"
> lockfile="${dbroot}/db.lck"
> localdb="${dbroot}/local"
>
> -# make sure pacman isn't running
> -if [[ -f $lockfile ]]; then
> +# make sure pacman isn't running and stop other instances for starting
> +exec 100<>"$lockfile"
> +if ! flock -x --nonblock 100; then
> + flock --close 100
> 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"
>
> workdir=$(mktemp -d "${TMPDIR:-/tmp}/pacman-optimize.XXXXXXXXXX") ||
> die_r "$(gettext "Can not create temp directory for database
> building.")\n" >&2
> @@ -178,6 +178,7 @@ rm -rf "$localdb.old"
>
> # remove the lock file and our working directory with sums and tarfile
> rm -f "$lockfile"
> +flock --close 100
> rm -rf "$workdir"
>
> echo
> --
> 1.8.3.4
>
>
