[ 38/56] n_gsm: uplink SKBs accumulate on list

From: Greg Kroah-Hartman
Date: Thu Oct 04 2012 - 17:18:31 EST


3.6-stable review patch. If anyone has any objections, please let me know.

------------------

From: Russ Gorby <russ.gorby@xxxxxxxxx>

commit 192b6041e75bb4a2aae73834037038cea139a92d upstream.

gsm_dlci_data_kick will not call any output function if tx_bytes > THRESH_LO
furthermore it will call the output function only once if tx_bytes == 0
If the size of the IP writes are on the order of THRESH_LO
we can get into a situation where skbs accumulate on the outbound list
being starved for events to call the output function.

gsm_dlci_data_kick now calls the sweep function when tx_bytes==0

Signed-off-by: Russ Gorby <russ.gorby@xxxxxxxxx>
Tested-by: Kappel, LaurentX <laurentx.kappel@xxxxxxxxx>
Signed-off-by: Alan Cox <alan@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/tty/n_gsm.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -971,16 +971,19 @@ static void gsm_dlci_data_sweep(struct g
static void gsm_dlci_data_kick(struct gsm_dlci *dlci)
{
unsigned long flags;
+ int sweep;

spin_lock_irqsave(&dlci->gsm->tx_lock, flags);
/* If we have nothing running then we need to fire up */
+ sweep = (dlci->gsm->tx_bytes < TX_THRESH_LO);
if (dlci->gsm->tx_bytes == 0) {
if (dlci->net)
gsm_dlci_data_output_framed(dlci->gsm, dlci);
else
gsm_dlci_data_output(dlci->gsm, dlci);
- } else if (dlci->gsm->tx_bytes < TX_THRESH_LO)
- gsm_dlci_data_sweep(dlci->gsm);
+ }
+ if (sweep)
+ gsm_dlci_data_sweep(dlci->gsm);
spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags);
}



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