s3:dbwrap_watch: also the fetch_locked case only needs to wake waiters just once

This is no change in behavior, because:

- The first dbwrap_do_locked(dbwrap_watched_record_wakeup_fn), is
  called at the start of dbwrap_watched_record_{storev,delete}().
  That means the nested dbwrap_do_locked() will pass the
  exact value same (unchanged) value to dbwrap_watched_record_wakeup_fn.

- After the first change we have either removed the whole backend
  record in dbwrap_watched_record_delete or dbwrap_watched_record_storev()
  removed all watchers and store num_watchers = 0.

- With that any further updates will have no watchers in the backend
  record, so dbwrap_do_locked(dbwrap_watched_record_wakeup_fn) will
  never do anything useful. It only burns cpu time any may cause memory
  fragmentation.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15125

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>

diff --git a/source3/lib/dbwrap/dbwrap_watch.c b/source3/lib/dbwrap/dbwrap_watch.c
index bad34686f118175c1bcab35691e745cf0caf4331..36c558564679d1c58beaa2399b8d4ecb463b0dd6 100644 (file)
--- a/source3/lib/dbwrap/dbwrap_watch.c
+++ b/source3/lib/dbwrap/dbwrap_watch.c
@@ -146,14 +146,13 @@ struct db_watched_record {
                TDB_DATA initial_value;
        } backend;
        struct dbwrap_watcher added;
-       bool within_do_locked;
        /*
         * This contains the initial value we got
         * passed to dbwrap_watched_do_locked_fn()
         *
         * It's only used in order to pass it
         * to dbwrap_watched_record_wakeup_fn()
-        * in dbwrap_watched_do_locked_{storev,delete}()
+        * in dbwrap_watched_{storev,delete}()
         *
         * It gets cleared after the first call to
         * dbwrap_watched_record_wakeup_fn() as we
@@ -216,6 +215,7 @@ static void db_watched_record_init(struct db_context *db,
                        .rec = backend_rec,
                        .initial_value = backend_value,
                },
+               .wakeup_value = backend_value,
        };
 
        ok = dbwrap_watch_rec_parse(backend_value,
@@ -388,8 +388,6 @@ static void dbwrap_watched_do_locked_fn(
        db_watched_record_init(state->db, state->msg_ctx,
                               &rec, &wrec,
                               backend_rec, backend_value);
-       wrec.within_do_locked = true;
-       wrec.wakeup_value = backend_value;
 
        state->fn(&rec, rec.value, state->private_data);
 
@@ -480,35 +478,19 @@ static void dbwrap_watched_record_wakeup(
        struct db_watched_record *wrec)
 {
        struct db_record *rec = wrec->rec;
-       struct db_context *backend = dbwrap_record_get_db(wrec->backend.rec);
-       TDB_DATA key = dbwrap_record_get_key(wrec->backend.rec);
        struct db_context *db = dbwrap_record_get_db(rec);
        struct db_watched_ctx *ctx = talloc_get_type_abort(
                db->private_data, struct db_watched_ctx);
        struct dbwrap_watched_record_wakeup_state state = {
                .msg_ctx = ctx->msg,
        };
-       NTSTATUS status;
-
-       if (wrec->within_do_locked) {
-               /*
-                * Wakeup only needs to happen once.
-                * so we clear wrec->wakeup_value after the first run
-                */
-               dbwrap_watched_record_wakeup_fn(rec, wrec->wakeup_value, &state);
-               wrec->wakeup_value = (TDB_DATA) { .dsize = 0, };
-               return;
-       }
 
-       status = dbwrap_do_locked(
-               backend,
-               key,
-               dbwrap_watched_record_wakeup_fn,
-               &state);
-       if (!NT_STATUS_IS_OK(status)) {
-               DBG_DEBUG("dbwrap_record_modify failed: %s\n",
-                         nt_errstr(status));
-       }
+       /*
+        * Wakeup only needs to happen once.
+        * so we clear wrec->wakeup_value after the first run
+        */
+       dbwrap_watched_record_wakeup_fn(rec, wrec->wakeup_value, &state);
+       wrec->wakeup_value = (TDB_DATA) { .dsize = 0, };
 }
 
 static NTSTATUS dbwrap_watched_record_storev(