Suspend exclusive database lock when scriptlets get called, allowing
read access in scriptlets. Only needed for DB_PRIVATE (aka global)
locking.

--- ./lib/backend/db3.c.orig	2012-06-01 10:50:11.000000000 +0000
+++ ./lib/backend/db3.c	2012-06-01 10:50:19.000000000 +0000
@@ -628,3 +628,59 @@ int dbiOpen(rpmdb rdb, rpmDbiTagVal rpmt
 
     return rc;
 }
+
+int dbiSuspendDBLock(dbiIndex dbi, unsigned int flags)
+{
+    struct flock l;
+    int rc = 0;
+    int fdno = -1;
+
+    if (!dbi->dbi_lockdbfd)
+	return 0;
+    if (!(dbi->dbi_rpmdb->db_mode & (O_RDWR|O_WRONLY)))
+	return 0;
+    if (_lockdbfd == 0)
+	return 0;
+    if (!(dbi->dbi_db->fd(dbi->dbi_db, &fdno) == 0 && fdno >= 0))
+	return 1;
+    memset(&l, 0, sizeof(l));
+    l.l_whence = 0;
+    l.l_start = 0;
+    l.l_len = 0;
+    l.l_type = F_RDLCK;
+    rc = fcntl(fdno, F_SETLK, (void *)&l);
+    if (rc)
+	rpmlog(RPMLOG_WARNING, _("could not suspend database lock\n"));
+    return rc;
+}
+
+int dbiResumeDBLock(dbiIndex dbi, unsigned int flags)
+{
+    struct flock l;
+    int rc = 0;
+    int tries;
+    int fdno = -1;
+
+    if (!dbi->dbi_lockdbfd)
+	return 0;
+    if (!(dbi->dbi_rpmdb->db_mode & (O_RDWR|O_WRONLY)))
+	return 0;
+    if (_lockdbfd == 0)
+	return 0;
+    if (!(dbi->dbi_db->fd(dbi->dbi_db, &fdno) == 0 && fdno >= 0))
+	return 1;
+    for (tries = 0; tries < 2; tries++) {
+	memset(&l, 0, sizeof(l));
+	l.l_whence = 0;
+	l.l_start = 0;
+	l.l_len = 0;
+	l.l_type = F_WRLCK;
+	rc = fcntl(fdno, tries ? F_SETLKW : F_SETLK, (void *)&l);
+	if (!rc)
+	    break;
+	if (tries == 0)
+	    rpmlog(RPMLOG_WARNING, _("waiting to reestablish exclusive database lock\n"));
+    }
+    return rc;
+}
+
--- ./lib/backend/dbi.h.orig	2012-03-20 08:07:25.000000000 +0000
+++ ./lib/backend/dbi.h	2012-06-01 10:53:43.000000000 +0000
@@ -90,6 +90,24 @@ struct dbiIndex_s {
 extern "C" {
 #endif
 
+/** \ingroup dbi
+ * Suspend the exclusive lock on the dbi
+ * @param dbi		index database handle
+ * @param flags		(unused)
+ * @return		0 on success
+ */
+RPM_GNUC_INTERNAL
+int dbiSuspendDBLock(dbiIndex dbi, unsigned int flags);
+
+/** \ingroup dbi
+ * Reacquire an exclusive lock on the dbi
+ * @param dbi		index database handle
+ * @param flags		(unused)
+ * @return		0 on success
+ */
+RPM_GNUC_INTERNAL
+int dbiResumeDBLock(dbiIndex dbi, unsigned int flags);
+
 
 RPM_GNUC_INTERNAL
 /* Globally enable/disable fsync in the backend */
--- ./lib/psm.c.orig	2012-06-01 10:50:11.000000000 +0000
+++ ./lib/psm.c	2012-06-01 10:51:34.000000000 +0000
@@ -419,10 +419,12 @@ static rpmRC runScript(rpmpsm psm, ARGV_
     if (sfd == NULL)
 	sfd = rpmtsScriptFd(psm->ts);
 
+    rpmtsSuspendResumeDBLock(psm->ts, 0);
     rpmswEnter(rpmtsOp(psm->ts, RPMTS_OP_SCRIPTLETS), 0);
     rc = rpmScriptRun(script, arg1, arg2, sfd,
 		      prefixes, warn_only, selinux);
     rpmswExit(rpmtsOp(psm->ts, RPMTS_OP_SCRIPTLETS), 0);
+    rpmtsSuspendResumeDBLock(psm->ts, 1);
 
     /* Map warn-only errors to "notfound" for script stop callback */
     stoprc = (rc != RPMRC_OK && warn_only) ? RPMRC_NOTFOUND : rc;
--- ./lib/rpmdb.c.orig	2012-06-01 10:50:11.000000000 +0000
+++ ./lib/rpmdb.c	2012-06-01 10:50:19.000000000 +0000
@@ -769,6 +769,12 @@ int rpmdbSync(rpmdb db)
     return dbiForeach(db->_dbi, dbiSync, 0);
 }
 
+int rpmdbSuspendResumeDBLock(rpmdb db, int mode)
+{
+    if (db == NULL) return 0;
+    return dbiForeach(db->_dbi, mode ? dbiResumeDBLock : dbiSuspendDBLock, 0);
+}
+
 static rpmdb newRpmdb(const char * root, const char * home,
 		      int mode, int perms, int flags)
 {
--- ./lib/rpmts.c.orig	2012-03-20 08:07:25.000000000 +0000
+++ ./lib/rpmts.c	2012-06-01 10:50:19.000000000 +0000
@@ -95,6 +95,11 @@ int rpmtsOpenDB(rpmts ts, int dbmode)
     return rc;
 }
 
+int rpmtsSuspendResumeDBLock(rpmts ts, int mode)
+{
+    return rpmdbSuspendResumeDBLock(ts->rdb, mode);
+}
+
 int rpmtsInitDB(rpmts ts, int dbmode)
 {
     rpmlock lock = rpmtsAcquireLock(ts);
--- ./lib/rpmts.h.orig	2012-03-20 08:07:25.000000000 +0000
+++ ./lib/rpmts.h	2012-06-01 10:50:19.000000000 +0000
@@ -423,6 +423,8 @@ rpmdb rpmtsGetRdb(rpmts ts);
 void * rpmtsNotify(rpmts ts, rpmte te,
                 rpmCallbackType what, rpm_loff_t amount, rpm_loff_t total);
 
+int rpmtsSuspendResumeDBLock(rpmts ts, int mode);
+
 /** \ingroup rpmts
  * Return number of (ordered) transaction set elements.
  * @param ts		transaction set