lib/dbwrap: rewrite lock order check to ease debugging

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Fri Aug  3 12:52:38 CEST 2012 on sn-devel-104

diff --git a/lib/dbwrap/dbwrap.c b/lib/dbwrap/dbwrap.c
index 4c0160a4740cfe931674d6f49879f3d59e2b9c61..0e0422c41b5e66a0c10cc9324b87266a3045f3c2 100644 (file)
--- a/lib/dbwrap/dbwrap.c
+++ b/lib/dbwrap/dbwrap.c
@@ -123,30 +123,49 @@ NTSTATUS dbwrap_record_delete(struct db_record *rec)
 }
 
 struct dbwrap_lock_order_state {
-       uint8_t *plock_order_mask;
-       uint8_t bitmask;
+       struct db_context **locked_dbs;
+       struct db_context *db;
 };
 
+static void debug_lock_order(int level, struct db_context *dbs[])
+{
+       int i;
+       DEBUG(level, ("lock order: "));
+       for (i=0; i<DBWRAP_LOCK_ORDER_MAX; i++) {
+               DEBUGADD(level, (" %d:%s", i + 1, dbs[i] ? dbs[i]->name : "<none>"));
+       }
+       DEBUGADD(level, ("\n"));
+}
+
 static int dbwrap_lock_order_state_destructor(
        struct dbwrap_lock_order_state *s)
 {
-       *s->plock_order_mask &= ~s->bitmask;
+       int idx = s->db->lock_order - 1;
+
+       DEBUG(5, ("release lock order %d for %s\n",
+                 (int)s->db->lock_order, s->db->name));
+
+       if (s->locked_dbs[idx] != s->db) {
+               DEBUG(0, ("locked db at lock order %d is %s, expected %s\n",
+                         idx + 1, s->locked_dbs[idx]->name, s->db->name));
+               debug_lock_order(0, s->locked_dbs);
+               smb_panic("inconsistent lock_order\n");
+       }
+
+       s->locked_dbs[idx] = NULL;
+
+       debug_lock_order(10, s->locked_dbs);
+
        return 0;
 }
 
+
 static struct dbwrap_lock_order_state *dbwrap_check_lock_order(
        struct db_context *db, TALLOC_CTX *mem_ctx)
 {
-       /*
-        * Store the lock_order of currently locked records as bits in
-        * "lock_order_mask". We only use levels 1,2,3 right now, so a
-        * single uint8_t is enough.
-        */
-       static uint8_t lock_order_mask;
-
-       struct dbwrap_lock_order_state *state;
-       uint8_t idx;
-       int used;
+       int idx;
+       static struct db_context *locked_dbs[DBWRAP_LOCK_ORDER_MAX];
+       struct dbwrap_lock_order_state *state = NULL;
 
        if (db->lock_order == 0) {
                /*
@@ -154,24 +173,28 @@ static struct dbwrap_lock_order_state *dbwrap_check_lock_order(
                 * real locking. Return state nevertheless to avoid
                 * special cases.
                 */
-               return talloc(mem_ctx, struct dbwrap_lock_order_state);
+               return talloc_zero(mem_ctx, struct dbwrap_lock_order_state);
        }
 
-       /*
-        * We fill bits from the high bits, to be able to use
-        * "ffs(lock_order_mask)"
-        */
-       idx = sizeof(lock_order_mask)*8 - db->lock_order;
+       if (db->lock_order > DBWRAP_LOCK_ORDER_MAX) {
+               DEBUG(0,("Invalid lock order %d of %s\n",
+                        (int)db->lock_order, db->name));
+               smb_panic("invalid lock_order\n");
+               return NULL;
+       }
 
-       used = ffs(lock_order_mask);
+       DEBUG(5, ("check lock order %d for %s\n",
+                 (int)db->lock_order, db->name));
 
-       DEBUG(5, ("used=%d, lock_order=%d, idx=%d\n", used,
-                 (int)db->lock_order, (int)idx));
 
-       if ((used != 0) && (used-1 <= idx)) {
-               DEBUG(0, ("Lock order violation: Trying %d, order_mask=%x\n",
-                         (int)db->lock_order, (int)lock_order_mask));
-               return NULL;
+       for (idx=db->lock_order - 1; idx < DBWRAP_LOCK_ORDER_MAX; idx++) {
+               if (locked_dbs[idx] != NULL) {
+                       DEBUG(0, ("Lock order violation: Trying %s at %d while %s at %d is locked\n",
+                                 db->name, (int)db->lock_order, locked_dbs[idx]->name, idx + 1));
+                       debug_lock_order(0, locked_dbs);
+                       smb_panic("invalid lock_order");
+                       return NULL;
+               }
        }
 
        state = talloc(mem_ctx, struct dbwrap_lock_order_state);
@@ -179,11 +202,13 @@ static struct dbwrap_lock_order_state *dbwrap_check_lock_order(
                DEBUG(1, ("talloc failed\n"));
                return NULL;
        }
-       state->bitmask = 1 << idx;
-       state->plock_order_mask = &lock_order_mask;
-
+       state->db = db;
+       state->locked_dbs = locked_dbs;
        talloc_set_destructor(state, dbwrap_lock_order_state_destructor);
-       lock_order_mask |= state->bitmask;
+
+       locked_dbs[db->lock_order - 1] = db;
+
+       debug_lock_order(10, locked_dbs);
 
        return state;
 }

diff --git a/lib/dbwrap/dbwrap.h b/lib/dbwrap/dbwrap.h
index 5244ff216cf4b519e833fb660133b1265fb851fa..3b0d61c92c7c21ca6af682449f7335450b4629dc 100644 (file)
--- a/lib/dbwrap/dbwrap.h
+++ b/lib/dbwrap/dbwrap.h
@@ -30,6 +30,7 @@ enum dbwrap_lock_order {
        DBWRAP_LOCK_ORDER_2 = 2,
        DBWRAP_LOCK_ORDER_3 = 3
 };
+#define DBWRAP_LOCK_ORDER_MAX DBWRAP_LOCK_ORDER_3
 
 /* The following definitions come from lib/dbwrap.c  */