Hello, Tetsuo.
On Sat, May 02, 2015 at 01:54:57PM +0900, Tetsuo Handa wrote:
> Tejun Heo wrote:
> > +For example,
> > +
> > + 6,416,1758426,-,ncfrag=0/33;the first chunk,
> > + 6,416,1758426,-,ncfrag=16/33;the second chunk.
> > +
>
> Wouldn't total-bytes > 1000 than 33 in this example?
It's trying to give an example on how the ncfrag header looks like but
yeah I'll tweak it a bit and add further explanation.
> > +/**
> > + * send_ext_msg_udp - send extended log message to target
> > + * @nt: target to send message to
> > + * @msg: extended log message to send
> > + * @msg_len: length of message
> > + *
> > + * Transfer extended log @msg to @nt. If @msg is longer than
> > + * MAX_PRINT_CHUNK, it'll be split and transmitted in multiple chunks with
> > + * ncfrag header field added to identify them.
> > + */
> > +static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg,
> > + int msg_len)
> > +{
> > + static char buf[MAX_PRINT_CHUNK];
> > + const int max_extra_len = sizeof(",ncfrag=0000/0000");
> > + const char *header, *body;
> > + int header_len = msg_len, body_len = 0;
> > + int chunk_len, nr_chunks, i;
> > +
> > + if (msg_len <= MAX_PRINT_CHUNK) {
> > + netpoll_send_udp(&nt->np, msg, msg_len);
> > + return;
> > + }
> > +
> > + /* need to insert extra header fields, detect header and body */
> > + header = msg;
> > + body = memchr(msg, ';', msg_len);
> > + if (body) {
> > + header_len = body - header;
> > + body_len = msg_len - header_len - 1;
> > + body++;
> > + }
> > +
> > + chunk_len = MAX_PRINT_CHUNK - header_len - max_extra_len;
> > + if (WARN_ON_ONCE(chunk_len <= 0))
> > + return;
>
> This path is executed only when msg_len > MAX_PRINT_CHUNK.
> And since header_len == msg_len if body == NULL, chunk_len <= 0 is true.
> We will hit this WARN_ON_ONCE() if memchr(msg, ';', msg_len) == NULL
> which will fail to send the message. Is this what you want?
Yeah, extended consoles should be fed messages w/ proper headers. If
not, we warn and bail.
> > +static void write_ext_msg(struct console *con, const char *msg,
> > + unsigned int len)
> > +{
> > + struct netconsole_target *nt;
> > + unsigned long flags;
> > +
> > + if ((oops_only && !oops_in_progress) || list_empty(&target_list))
> > + return;
> > +
> > + spin_lock_irqsave(&target_list_lock, flags);
> > + list_for_each_entry(nt, &target_list, list)
>
> Don't you need to call netconsole_target_get() here
>
> > + if (nt->extended && nt->enabled && netif_running(nt->np.dev))
> > + send_ext_msg_udp(nt, msg, len);
>
> and netconsole_target_put() here as with write_msg()?
Ah, I dropped the patch which removed it from write_msg() but the
following pattern doesn't do anything. It's just pure confusion.
lock;
ref++ on an item on the index;
do something w/o releasing lock;
ref-- on the item;
unlock;
netconsole_netdev_event() has to release lock to process the item so
refcnting is needed there. It got duplicated in write_msg() for no
reason. I'll add a patch to remove it.
Thanks.
--
tejun
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