Allow us to "lock" printer tdb entries in memory to stop them being

re-used as cache.
Jeremy.
(This used to be commit 6f901e479dd7a0b9d1395aad5b8ef028c0514fec)

diff --git a/source3/printing/printing.c b/source3/printing/printing.c
index cb689c05d6636bec15f554424db2c55f67009fe9..61c328219695bedf85ff4deef552b86ddd475ce4 100644 (file)
--- a/source3/printing/printing.c
+++ b/source3/printing/printing.c
@@ -132,11 +132,13 @@ static pid_t local_pid;
 
 static int get_queue_status(int, print_status_struct *);
 
+/* There can be this many printing tdb's open, plus any locked ones. */
 #define MAX_PRINT_DBS_OPEN 1
 
 struct tdb_print_db {
        struct tdb_print_db *next, *prev;
        TDB_CONTEXT *tdb;
+       int locked;
        fstring printer_name;
 };
 
@@ -149,7 +151,7 @@ static struct tdb_print_db *print_db_head;
 
 static struct tdb_print_db *get_print_db_byname(const char *printername)
 {
-       struct tdb_print_db *p, *last_entry;
+       struct tdb_print_db *p = NULL, *last_entry = NULL;
        int num_open = 0;
        pstring printdb_path;
 
@@ -161,20 +163,28 @@ static struct tdb_print_db *get_print_db_byname(const char *printername)
                num_open++;
                last_entry = p;
        }
+
        /* Not found. */
        if (num_open >= MAX_PRINT_DBS_OPEN) {
-               /* Recycle the last entry. */
+               /* Try and recycle the last entry. */
                DLIST_PROMOTE(print_db_head, last_entry);
-               if (print_db_head->tdb) {
-                       if (tdb_close(print_db_head->tdb)) {
-                               DEBUG(0,("get_print_db: Failed to close tdb for printer %s\n",
-                                                       print_db_head->printer_name ));
-                               return NULL;
+
+               for (p = print_db_head; p; p = p->next) {
+                       if (p->locked)
+                               continue;
+                       if (p->tdb) {
+                               if (tdb_close(print_db_head->tdb)) {
+                                       DEBUG(0,("get_print_db: Failed to close tdb for printer %s\n",
+                                                               print_db_head->printer_name ));
+                                       return NULL;
+                               }
+                               ZERO_STRUCTP(p);
+                               DLIST_PROMOTE(print_db_head, p);
                        }
                }
-               p = print_db_head;
-               ZERO_STRUCTP(p);
-       } else {
+       }
+       
+       if (!p) {
                /* Create one. */
                p = (struct tdb_print_db *)malloc(sizeof(struct tdb_print_db));
                if (!p) {
@@ -204,6 +214,30 @@ static struct tdb_print_db *get_print_db_byname(const char *printername)
        return p;
 }
 
+/****************************************************************************
+ Lock a pdb entry by string.
+****************************************************************************/
+
+static int pdb_entry_lock(struct tdb_print_db *pdb, char *key)
+{
+       if (pdb->locked == 0) {
+               if (tdb_lock_bystring(pdb->tdb, key) == -1)
+                       return -1;
+       }
+       pdb->locked++;
+}
+
+/****************************************************************************
+ Unlock a pdb entry by string.
+****************************************************************************/
+
+static void pdb_entry_unlock(struct tdb_print_db *pdb, char *key)
+{
+       pdb->locked--;
+       if (pdb->locked == 0)
+               tdb_unlock_bystring(pdb->tdb, key);
+}
+
 /****************************************************************************
  Initialise the printing backend. Called once at startup. 
  Does not survive a fork
@@ -235,12 +269,15 @@ BOOL print_backend_init(void)
                pdb = get_print_db_byname(lp_const_servicename(snum));
                if (!pdb)
                        continue;
-               tdb_lock_bystring(pdb->tdb, sversion);
+               if (pdb_entry_lock(pdb, sversion) == -1) {
+                       DEBUG(0,("print_backend_init: Failed to open printer %s database\n", lp_const_servicename(snum) ));
+                       return False;
+               }
                if (tdb_fetch_int32(pdb->tdb, sversion) != PRINT_DATABASE_VERSION) {
                        tdb_traverse(pdb->tdb, tdb_traverse_delete_fn, NULL);
                        tdb_store_int32(pdb->tdb, sversion, PRINT_DATABASE_VERSION);
                }
-               tdb_unlock_bystring(pdb->tdb, sversion);
+               pdb_entry_unlock(pdb, sversion);
        }
 
        /* select the appropriate printing interface... */
@@ -746,7 +783,10 @@ static void print_queue_update(int snum)
        /* Lock the queue for the database update */
 
        slprintf(keystr, sizeof(keystr) - 1, "LOCK/%s", printer_name);
-       tdb_lock_bystring(pdb->tdb, keystr);
+       if (pdb_entry_lock(pdb, keystr) == -1) {
+               DEBUG(0,("print_queue_update: Failed to lock printer %s database\n", printer_name));
+               return;
+       }
 
        /*
         * Ensure that no one else got in here.
@@ -758,7 +798,7 @@ static void print_queue_update(int snum)
                /*
                 * Someone else is doing the update, exit.
                 */
-               tdb_unlock_bystring(pdb->tdb, keystr);
+               pdb_entry_unlock(pdb, keystr);
                return;
        }
 
@@ -774,7 +814,7 @@ static void print_queue_update(int snum)
         * the update.
         */
 
-       tdb_unlock_bystring(pdb->tdb, keystr);
+       pdb_entry_unlock(pdb, keystr);
 
        /*
         * Update the cache time FIRST ! Stops others even
@@ -1335,7 +1375,10 @@ uint32 print_job_start(struct current_user *user, int snum, char *jobname)
        fstrcpy(pjob.queuename, lp_const_servicename(snum));
 
        /* lock the database */
-       tdb_lock_bystring(pdb->tdb, "INFO/nextjob");
+       if (pdb_entry_lock(pdb, "INFO/nextjob") == -1) {
+               DEBUG(0,("print_job_start: failed to lock printing database %s\n", printername ));
+               return (uint32)-1;
+       }
 
        next_jobid = tdb_fetch_int32(pdb->tdb, "INFO/nextjob");
        if (next_jobid == -1)
@@ -1378,7 +1421,7 @@ to open spool file %s.\n", pjob.filename));
 
        pjob_store(snum, jobid, &pjob);
 
-       tdb_unlock_bystring(pdb->tdb, "INFO/nextjob");
+       pdb_entry_unlock(pdb, "INFO/nextjob");
 
        /*
         * If the printer is marked as postscript output a leading
@@ -1397,7 +1440,7 @@ to open spool file %s.\n", pjob.filename));
        if (jobid != -1)
                pjob_delete(snum, jobid);
 
-       tdb_unlock_bystring(pdb->tdb, "INFO/nextjob");
+       pdb_entry_unlock(pdb, "INFO/nextjob");
 
        DEBUG(3, ("print_job_start: returning fail. Error = %s\n", strerror(errno) ));
        return -1;