Re: [PATCH v2 3/3] pppoatm: protect against freeing of vcc

On Wed, 2012-11-28 at 09:21 +0000, David Laight wrote:

quoted

Even when it might make sense to sleep in close until tx drains
there needs to be a finite timeout before it become abortive.

You are, of course, right. We should never wait for hardware for ever.
And just to serve me right, I seem to have hit a bug in the latest Solos
firmware (1.11) which makes it sometimes lock up when I reboot. So it
never responds to the PKT_PCLOSE packet... and thus it deadlocks when I
try to kill pppd and unload the module to reset it :)

New version...

From 53dd01c08fec5b26006a009b25e4210127fdb27a Mon Sep 17 00:00:00 2001
From: David Woodhouse <redacted>
Date: Tue, 27 Nov 2012 23:49:24 +0000
Subject: [PATCH] solos-pci: Wait for pending TX to complete when releasing
 vcc

We should no longer be calling the old pop routine for the vcc, after
vcc_release() has completed. Make sure we wait for any pending TX skbs
to complete, by waiting for our own PKT_PCLOSE control skb to be sent.

Signed-off-by: David Woodhouse <redacted>
---
 drivers/atm/solos-pci.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/atm/solos-pci.c b/drivers/atm/solos-pci.c
index 9851093..3720670 100644
--- a/drivers/atm/solos-pci.c
+++ b/drivers/atm/solos-pci.c

@@ -92,6 +92,7 @@ struct pkt_hdr {
 };
 
 struct solos_skb_cb {
+	struct completion c;
 	struct atm_vcc *vcc;
 	uint32_t dma_addr;
 };

@@ -881,11 +882,18 @@ static void pclose(struct atm_vcc *vcc)
 	header->vci = cpu_to_le16(vcc->vci);
 	header->type = cpu_to_le16(PKT_PCLOSE);
 
+	init_completion(&SKB_CB(skb)->c);
+
 	fpga_queue(card, SOLOS_CHAN(vcc->dev), skb, NULL);
 
 	clear_bit(ATM_VF_ADDR, &vcc->flags);
 	clear_bit(ATM_VF_READY, &vcc->flags);
 
+	if (!wait_for_completion_timeout(&SKB_CB(skb)->c,
+					 jiffies + msecs_to_jiffies(5000)))
+		dev_warn(&card->dev->dev, "Timeout waiting for VCC close on port %d\n",
+			 SOLOS_CHAN(vcc->dev));
+