From 268e526b935e794386d75025577b745e6bd57f13 Mon Sep 17 00:00:00 2001 From: Mikhail Kshevetskiy Date: Fri, 23 Sep 2011 19:22:56 +0400 Subject: [PATCH] tty/n_gsm: avoid fifo overflow in gsm_dlci_data_output n_gsm use a simple approach: every writing to fifo correspond exactly one reading from fifo. There are no problem in this approach until we read less bytes then we write. As result fifo may owerflow. This leads to packet loss and very slow responce. For example, this happens with ping packets (about 96 byte each) and default gsm->mtu = 64. As result we get 50 sec ping timeout and 20% packet loss. Fix the problem by reading and sending all data from the fifo Signed-off-by: Mikhail Kshevetskiy Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_gsm.c | 52 ++++++++++++++++++++++++--------------------- 1 file changed, 28 insertions(+), 24 deletions(-) diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 14c26cdd8aca..4cb0d0a3e57b 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -809,37 +809,41 @@ static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci) { struct gsm_msg *msg; u8 *dp; - int len, size; + int len, total_size, size; int h = dlci->adaption - 1; - len = kfifo_len(dlci->fifo); - if (len == 0) - return 0; + total_size = 0; + while(1) { + len = kfifo_len(dlci->fifo); + if (len == 0) + return total_size; - /* MTU/MRU count only the data bits */ - if (len > gsm->mtu) - len = gsm->mtu; + /* MTU/MRU count only the data bits */ + if (len > gsm->mtu) + len = gsm->mtu; - size = len + h; + size = len + h; - msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype); - /* FIXME: need a timer or something to kick this so it can't - get stuck with no work outstanding and no buffer free */ - if (msg == NULL) - return -ENOMEM; - dp = msg->data; - switch (dlci->adaption) { - case 1: /* Unstructured */ - break; - case 2: /* Unstructed with modem bits. Always one byte as we never - send inline break data */ - *dp++ = gsm_encode_modem(dlci); - break; + msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype); + /* FIXME: need a timer or something to kick this so it can't + get stuck with no work outstanding and no buffer free */ + if (msg == NULL) + return -ENOMEM; + dp = msg->data; + switch (dlci->adaption) { + case 1: /* Unstructured */ + break; + case 2: /* Unstructed with modem bits. Always one byte as we never + send inline break data */ + *dp++ = gsm_encode_modem(dlci); + break; + } + WARN_ON(kfifo_out_locked(dlci->fifo, dp , len, &dlci->lock) != len); + __gsm_data_queue(dlci, msg); + total_size += size; } - WARN_ON(kfifo_out_locked(dlci->fifo, dp , len, &dlci->lock) != len); - __gsm_data_queue(dlci, msg); /* Bytes of data we used up */ - return size; + return total_size; } /**