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

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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>
This commit is contained in:
Stefan Metzmacher 2022-06-24 15:33:30 +00:00 committed by Ralph Boehme
parent 726f468ccd
commit 6e45da1a38
1 changed files with 8 additions and 26 deletions
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34
source3/lib/dbwrap/dbwrap_watch.c
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@ -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(