From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Marek Lindner Date: Thu, 26 Apr 2012 13:49:29 +0800 References: <1335170112-6610-1-git-send-email-lindner_marek@yahoo.de> <20120424131556.GD1015@ritirata.org> In-Reply-To: <20120424131556.GD1015@ritirata.org> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Message-Id: <201204261349.30120.lindner_marek@yahoo.de> Subject: Re: [B.A.T.M.A.N.] [RFC] batman-adv: turn tt commit code into routing protocol agnostic API Reply-To: The list for a Better Approach To Mobile Ad-hoc Networking List-Id: The list for a Better Approach To Mobile Ad-hoc Networking List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: The list for a Better Approach To Mobile Ad-hoc Networking Hi, > thank you for your effort in improving the TT code :) I try to make the TT code a better place. ;-) > > + if (hard_iface == primary_if) > > + tt_num_changes = tt_append_changes(bat_priv, > > + &hard_iface->packet_buff, > > + &hard_iface->packet_len, > > + BATMAN_OGM_HLEN); > > + > > + if (tt_num_changes > 0) > > + batman_ogm_packet->tt_num_changes = tt_num_changes; > > + else > > + batman_ogm_packet->tt_num_changes = 0; > > Do we really need this if-loop? Am I wrong or tt_num_changes can only be >= > 0 ? Right, strictly speaking it is not needed. However, tt_append_changes() is defined as returning int, hence the calling function can't rely on this assumption. > > -int tt_changes_fill_buffer(struct bat_priv *bat_priv, > > - unsigned char *buff, int buff_len) > > +static void tt_realloc_packet_buff(unsigned char **packet_buff, > > + int *packet_buff_len, int min_packet_len, > > + int new_packet_len) > > +{ > > + unsigned char *new_buff; > > + > > + new_buff = kmalloc(new_packet_len, GFP_ATOMIC); > > + > > + /* keep old buffer if kmalloc should fail */ > > + if (new_buff) { > > + memcpy(new_buff, *packet_buff, min_packet_len); > > + kfree(*packet_buff); > > + *packet_buff = new_buff; > > + *packet_buff_len = new_packet_len; > > + } > > I took quite a while to understand what happens to packet_buff_len if > kmalloc failed. Actually it correctly stores the "previous" buffer size, so > the rest of the code will handle kmalloc failures the right way. :) Actually, this part of the code did not change. Check realloc_packet_buffer() in send.c and you will find the same function. > > +} > > + > > +static void tt_prepare_packet_buff(struct bat_priv *bat_priv, > > + unsigned char **packet_buff, > > + int *packet_buff_len, int min_packet_len) > > +{ > > + struct hard_iface *primary_if; > > + int req_len; > > + > > + primary_if = primary_if_get_selected(bat_priv); > > + > > + req_len = min_packet_len; > > + req_len += tt_len((uint8_t)atomic_read(&bat_priv->tt_local_changes)); > > This cast is also in the current code. But why not removing it? atomic_t is > an int, the tt_len() argument too. No idea why the cast is there. I'll remove it. :-) > > + > > + /* if we have too many changes for one packet don't send any > > + * and wait for the tt table request which will be fragmented */ > > please fix this comment. */ must be on a new line. Ok, I'll fix it. Just a quick reminder that this is old code as well .. > > +static int tt_changes_fill_buff(struct bat_priv *bat_priv, > > + unsigned char **packet_buff, > > + int *packet_buff_len, int min_packet_len) > > > > { > > > > - int count = 0, tot_changes = 0; > > > > struct tt_change_node *entry, *safe; > > > > + int count = 0, tot_changes = 0, new_len; > > + unsigned char *tt_buff; > > + > > As suggesting on IRC we should lock the "read and copy procedure". > I'd call lock() here. > > > + tt_prepare_packet_buff(bat_priv, packet_buff, > > + packet_buff_len, min_packet_len); > > > > - if (buff_len > 0) > > - tot_changes = buff_len / tt_len(1); > > + new_len = *packet_buff_len - min_packet_len; > > > > > > > > + tt_buff = *packet_buff + min_packet_len; > > + > > + if (new_len > 0) > > + tot_changes = new_len / tt_len(1); > > > > spin_lock_bh(&bat_priv->tt_changes_list_lock); > > atomic_set(&bat_priv->tt_local_changes, 0); > > > > @@ -290,7 +339,7 @@ int tt_changes_fill_buffer(struct bat_priv *bat_priv, > > > > list_for_each_entry_safe(entry, safe, &bat_priv->tt_changes_list, > > > > list) { > > > > if (count < tot_changes) { > > > > - memcpy(buff + tt_len(count), > > + memcpy(tt_buff + tt_len(count), > > > > &entry->change, sizeof(struct tt_change)); > > > > count++; > > > > } > > and I'd call unlock() after having copied everything to the tt_buff and > emptied the changes list. Can we directly use > bat_priv->tt_changes_list_lock ? It seems to be the case :) I'd rather move the locking into a separate patch to make it easier to trace the change. > > > > /* all the reset entries have now to be effectively counted as local > > > > * entries */ > > > > atomic_add(changed_num, &bat_priv->num_local_tt); > > tt_local_purge_pending_clients(bat_priv); > > > > + bat_priv->tt_crc = tt_local_crc(bat_priv); > > > > /* Increment the TTVN only once per OGM interval */ > > atomic_inc(&bat_priv->ttvn); > > bat_dbg(DBG_TT, bat_priv, "Local changes committed, updating to ttvn > > %u\n", > > > > (uint8_t)atomic_read(&bat_priv->ttvn)); > > > > bat_priv->tt_poss_change = false; > > > > + > > + /* reset the sending counter */ > > + atomic_set(&bat_priv->tt_ogm_append_cnt, TT_OGM_APPEND_MAX); > > + > > + return tt_changes_fill_buff(bat_priv, packet_buff, > > + packet_buff_len, packet_min_len); > > +} > > As you suggested on IRC, we may want to envelop this function with a > lock/unlock to force exclusive access to the local table and to the event > list. > > We should apply the same lock in tt_local_add()/del() I think. Why do want to lock tt_changes_fill_buff() and tt_commit_changes() separately? We should already lock in tt_commit_changes() because the entire commit has to be an atomic operation. Several of the function calls in tt_commit_changes() depend on the fact that no client is purged or added while these functions run. Thanks for your comments! Cheers, Marek