emo/xbps
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Use a POSIX lock for pkgdb and only issue pkgdb writes in exact points.

Browse Source 
- Rather than using a POSIX named semaphore use a POSIX lock (lockf(3))
for pkgdb for writers. Writers that cannot acquire the pkgdb lock will
get EAGAIN rather then being blocked.

- Due to using a file lock we cannot write the pkgdb every time a package
is being unpacked, configured or removed. Instead pkgdb is only written
at the end of a specific point in the transaction (unpack, configure, remove)
or via xbps_pkgdb_unlock().
This commit is contained in:
Juan RP
2014-03-04 14:37:10 +01:00
parent 6335573180
commit 0416b067d0
11 changed files with 85 additions and 101 deletions
Download Patch File Download Diff File Expand all files Collapse all files

74
lib/pkgdb.c
View File

@ -57,29 +57,49 @@
* data type is specified on its edge, i.e array, bool, integer, string,
* dictionary.
*/
#define _PKGDB_SEMNAME "/libxbps-pkgdb"
static int pkgdb_fd;
int
xbps_pkgdb_lock(struct xbps_handle *xhp)
{
int rv = 0;
mode_t myumask;
int rv;
/*
* Create/open the POSIX named semaphore.
* Use a mandatory file lock to only allow one writer to pkgdb,
* other writers will block.
*/
myumask = umask(0);
xhp->pkgdb_sem = sem_open(_PKGDB_SEMNAME, O_CREAT, 0660, 1);
umask(myumask);
xhp->pkgdb_plist = xbps_xasprintf("%s/%s", xhp->metadir, XBPS_PKGDB);
if (xbps_pkgdb_init(xhp) == ENOENT) {
/* if metadir does not exist, create it */
if (access(xhp->metadir, R_OK|X_OK) == -1) {
if (errno != ENOENT)
return errno;
if (xhp->pkgdb_sem == SEM_FAILED) {
if (xbps_mkpath(xhp->metadir, 0755) == -1) {
rv = errno;
xbps_dbg_printf(xhp, "[pkgdb] failed to create metadir "
"%s: %s\n", xhp->metadir, strerror(rv));
return rv;
}
}
/* if pkgdb is unexistent, create it with an empty dictionary */
xhp->pkgdb = xbps_dictionary_create();
if (!xbps_dictionary_externalize_to_file(xhp->pkgdb, xhp->pkgdb_plist)) {
rv = errno;
xbps_dbg_printf(xhp, "[pkgdb] failed to create pkgdb "
"%s: %s\n", xhp->pkgdb_plist, strerror(rv));
return rv;
}
}
if ((pkgdb_fd = open(xhp->pkgdb_plist, O_CREAT|O_RDWR, 0664)) == -1) {
rv = errno;
xbps_dbg_printf(xhp, "pkgdb: failed to create/open named "
"semaphore: %s\n", strerror(errno));
xbps_dbg_printf(xhp, "[pkgdb] cannot open pkgdb for locking "
"%s: %s\n", xhp->pkgdb_plist, strerror(rv));
free(xhp->pkgdb_plist);
return rv;
}
if (sem_wait(xhp->pkgdb_sem) == -1) {
if (lockf(pkgdb_fd, F_TLOCK, 0) == -1) {
rv = errno;
xbps_dbg_printf(xhp, "pkgdb: failed to lock named semaphore: %s\n",
strerror(errno));
xbps_dbg_printf(xhp, "[pkgdb] cannot lock pkgdb: %s\n", strerror(rv));
return rv;
}
return 0;
@ -88,16 +108,14 @@ xbps_pkgdb_lock(struct xbps_handle *xhp)
void
xbps_pkgdb_unlock(struct xbps_handle *xhp)
{
/* Unlock semaphore, close and destroy it (if possible) */
if (xhp->pkgdb_sem == NULL)
return;
(void)xbps_pkgdb_update(xhp, true);
sem_post(xhp->pkgdb_sem);
sem_close(xhp->pkgdb_sem);
sem_unlink(_PKGDB_SEMNAME);
xhp->pkgdb_sem = NULL;
if (lockf(pkgdb_fd, F_ULOCK, 0) == -1)
xbps_dbg_printf(xhp, "[pkgdb] failed to unlock pkgdb: %s\n", strerror(errno));
(void)close(pkgdb_fd);
pkgdb_fd = -1;
}
#undef _PKGDB_SEMNAME
int HIDDEN
xbps_pkgdb_init(struct xbps_handle *xhp)
@ -125,23 +143,19 @@ int
xbps_pkgdb_update(struct xbps_handle *xhp, bool flush)
{
xbps_dictionary_t pkgdb_storage;
char *plist;
static int cached_rv;
int rv = 0;
if (cached_rv && !flush)
return cached_rv;
plist = xbps_xasprintf("%s/%s", xhp->metadir, XBPS_PKGDB);
if (xhp->pkgdb && flush) {
pkgdb_storage = xbps_dictionary_internalize_from_file(plist);
pkgdb_storage = xbps_dictionary_internalize_from_file(xhp->pkgdb_plist);
if (pkgdb_storage == NULL ||
!xbps_dictionary_equals(xhp->pkgdb, pkgdb_storage)) {
/* flush dictionary to storage */
if (!xbps_dictionary_externalize_to_file(xhp->pkgdb, plist)) {
free(plist);
if (!xbps_dictionary_externalize_to_file(xhp->pkgdb, xhp->pkgdb_plist))
return errno;
}
}
if (pkgdb_storage)
xbps_object_release(pkgdb_storage);
@ -151,7 +165,7 @@ xbps_pkgdb_update(struct xbps_handle *xhp, bool flush)
cached_rv = 0;
}
/* update copy in memory */
if ((xhp->pkgdb = xbps_dictionary_internalize_from_file(plist)) == NULL) {
if ((xhp->pkgdb = xbps_dictionary_internalize_from_file(xhp->pkgdb_plist)) == NULL) {
if (errno == ENOENT)
xhp->pkgdb = xbps_dictionary_create();
else
@ -159,7 +173,6 @@ xbps_pkgdb_update(struct xbps_handle *xhp, bool flush)
cached_rv = rv = errno;
}
free(plist);
return rv;
}
@ -172,6 +185,9 @@ xbps_pkgdb_release(struct xbps_handle *xhp)
if (xhp->pkgdb == NULL)
return;
/* write pkgdb to storage in case it was modified */
(void)xbps_pkgdb_update(xhp, true);
if (xbps_object_type(xhp->pkg_metad) == XBPS_TYPE_DICTIONARY)
xbps_object_release(xhp->pkg_metad);