[PATCH] cli()/sti() fix for drivers/net/depca.c

[PATCH] cli()/sti() fix for drivers/net/depca.c

[Denis Vlasenko]

These are my first patches for network drivers.
Please comment if I'm doing something wrong.
Compile tested. Testers with hw wanted.
--
vda

diff -u --recursive linux-2.5.38orig/drivers/net/depca.c linux-2.5.38/drivers/net/depca.c
--- linux-2.5.38orig/drivers/net/depca.c	Sun Sep 22 04:25:10 2002
+++ linux-2.5.38/drivers/net/depca.c	Wed Oct  2 01:16:57 2002
@@ -1910,6 +1910,7 @@
   struct depca_ioctl *ioc = (struct depca_ioctl *) &rq->ifr_data;
   int i, status = 0;
   u_long ioaddr = dev->base_addr;
+  unsigned long flags;
   union {
     u8  addr[(HASH_TABLE_LEN * ETH_ALEN)];
     u16 sval[(HASH_TABLE_LEN * ETH_ALEN) >> 1];
@@ -1999,18 +2000,19 @@
     break;

   case DEPCA_GET_STATS:              /* Get the driver statistics */
-    cli();
+
+    spin_lock_irqsave(&lp->lock, flags);
     ioc->len = sizeof(lp->pktStats);
     if (copy_to_user(ioc->data, &lp->pktStats, ioc->len))
       status = -EFAULT;
-    sti();
+    spin_unlock_irqrestore(&lp->lock, flags);
     break;

   case DEPCA_CLR_STATS:              /* Zero out the driver statistics */
     if (!capable(CAP_NET_ADMIN)) return -EPERM;
-    cli();
+    spin_lock_irqsave(&lp->lock, flags);
     memset(&lp->pktStats, 0, sizeof(lp->pktStats));
-    sti();
+    spin_unlock_irqrestore(&lp->lock, flags);
     break;

   case DEPCA_GET_REG:                /* Get the DEPCA Registers */

Re: [PATCH] cli()/sti() fix for drivers/net/depca.c

[Francois Romieu]

Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua> :
> diff -u --recursive linux-2.5.38orig/drivers/net/depca.c linux-2.5.38/drivers/net/depca.c
> --- linux-2.5.38orig/drivers/net/depca.c	Sun Sep 22 04:25:10 2002
> +++ linux-2.5.38/drivers/net/depca.c	Wed Oct  2 01:16:57 2002
[...]
> @@ -1999,18 +2000,19 @@
>      break;
> 
>    case DEPCA_GET_STATS:              /* Get the driver statistics */
> -    cli();
> +
> +    spin_lock_irqsave(&lp->lock, flags);
>      ioc->len = sizeof(lp->pktStats);
>      if (copy_to_user(ioc->data, &lp->pktStats, ioc->len))
>        status = -EFAULT;
> -    sti();
> +    spin_unlock_irqrestore(&lp->lock, flags);

- copy_to_user() may sleep. Sleeping with spinlock held hurts badly.
- on SMP, pktStat can be updated while the copy progresses, see depca_rx().

-- 
Ueimor

Re: [PATCH] cli()/sti() fix for drivers/net/depca.c

[Denis Vlasenko]

On 2 October 2002 18:40, Francois Romieu wrote:
> Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua> :
> > diff -u --recursive linux-2.5.38orig/drivers/net/depca.c
> > linux-2.5.38/drivers/net/depca.c ---
> > linux-2.5.38orig/drivers/net/depca.c	Sun Sep 22 04:25:10 2002 +++
> > linux-2.5.38/drivers/net/depca.c	Wed Oct  2 01:16:57 2002
>
> [...]
>
> > @@ -1999,18 +2000,19 @@
> >      break;
> >
> >    case DEPCA_GET_STATS:              /* Get the driver statistics */
> > -    cli();
> > +
> > +    spin_lock_irqsave(&lp->lock, flags);
> >      ioc->len = sizeof(lp->pktStats);
> >      if (copy_to_user(ioc->data, &lp->pktStats, ioc->len))
> >        status = -EFAULT;
> > -    sti();
> > +    spin_unlock_irqrestore(&lp->lock, flags);

Did I say it's my first network patch? :-)

> - copy_to_user() may sleep. Sleeping with spinlock held hurts badly.

Ho to do it properly? Make a copy on stack under lock, release lock,
proceed with copy_to_user? That's 88 bytes at least...

> - on SMP, pktStat can be updated while the copy progresses, see depca_rx().

Should I place these pktStat updates under lp->lock?
--
vda

Re: [PATCH] cli()/sti() fix for drivers/net/depca.c

[Francois Romieu]

Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua> :
[...]
> Ho to do it properly? Make a copy on stack under lock, release lock,
> proceed with copy_to_user? That's 88 bytes at least...

Please see ETHTOOL_GSTATS usage in drivers/net/8139cp.c.

> > - on SMP, pktStat can be updated while the copy progresses, see depca_rx().
> 
> Should I place these pktStat updates under lp->lock?

You may.

depca_rx() looks strange:
buf = skb_put(skb, len);
[...]
netif_rx(skb);
[...]
if (buf[0] & ...)

-- 
Ueimor

Re: [PATCH] cli()/sti() fix for drivers/net/depca.c

[Denis Vlasenko]

On 2 October 2002 20:12, Francois Romieu wrote:
> Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua> :
> [...]
>
> > Ho to do it properly? Make a copy on stack under lock, release
> > lock, proceed with copy_to_user? That's 88 bytes at least...
>
> Please see ETHTOOL_GSTATS usage in drivers/net/8139cp.c.

This:
                tmp_stats = kmalloc(sz, GFP_KERNEL);
                if (!tmp_stats) return -ENOMEM;
                memset(tmp_stats, 0, sz);

                i = 0;
                tmp_stats[i++] = le64_to_cpu(cp->nic_stats->tx_ok);
                tmp_stats[i++] = le64_to_cpu(cp->nic_stats->rx_ok);
		...
                tmp_stats[i++] = le16_to_cpu(cp->nic_stats->tx_underrun);
                tmp_stats[i++] = cp->cp_stats.rx_frags;
                if (i != CP_NUM_STATS) BUG();

                i = copy_to_user(useraddr + sizeof(estats), tmp_stats, sz);
                kfree(tmp_stats);

kmalloc() isn't very fast, but I suppose ioctl is not that critical.

> > > - on SMP, pktStat can be updated while the copy progresses, see
> > > depca_rx().
> >
> > Should I place these pktStat updates under lp->lock?
>
> You may.
>
> depca_rx() looks strange:
> buf = skb_put(skb, len);
> [...]
> netif_rx(skb);
> [...]
> if (buf[0] & ...)

I'd say this network stuff is a bit cryptic for untrained eye :-)
What's strange with that code?

BTW, is there some (downloadable) book on Linux networking
internals?
--
vda

Re: [PATCH] cli()/sti() fix for drivers/net/depca.c

[Francois Romieu]

Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua> :
[...]
> > depca_rx() looks strange:
> > buf = skb_put(skb, len);
> > [...]
> > netif_rx(skb);
> > [...]
> > if (buf[0] & ...)
> 
> I'd say this network stuff is a bit cryptic for untrained eye :-)
> What's strange with that code?

One shouldn't assume the buffer is available once it was passed to 
netif_rx().

-- 
Ueimor

Re: [PATCH] cli()/sti() fix for drivers/net/depca.c

[Denis Vlasenko]

On 2 October 2002 20:12, Francois Romieu wrote:
> Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua> :
> [...]
>
> > Ho to do it properly? Make a copy on stack under lock, release
> > lock, proceed with copy_to_user? That's 88 bytes at least...
>
> Please see ETHTOOL_GSTATS usage in drivers/net/8139cp.c.
>
> > > - on SMP, pktStat can be updated while the copy progresses, see
> > > depca_rx().
> >
> > Should I place these pktStat updates under lp->lock?
>
> You may.

It's already under the lock: depca_rx is called from depca_interrupt
which acqures the lock.

New patch attached. Testers with hw wanted ;-)
--
vda

diff -u --recursive linux-2.5.40org/drivers/net/depca.c linux-2.5.40/drivers/net/depca.c
--- linux-2.5.40org/drivers/net/depca.c	Tue Oct  1 05:07:01 2002
+++ linux-2.5.40/drivers/net/depca.c	Thu Oct  3 10:52:09 2002
@@ -951,6 +951,7 @@
 }
 
 
+/* Called with lp->lock held */
 static int
 depca_rx(struct net_device *dev)
 {
@@ -1052,6 +1053,7 @@
 
 /*
 ** Buffer sent - check for buffer errors.
+** Called with lp->lock held
 */
 static int
 depca_tx(struct net_device *dev)
@@ -1910,6 +1912,7 @@
   struct depca_ioctl *ioc = (struct depca_ioctl *) &rq->ifr_data;
   int i, status = 0;
   u_long ioaddr = dev->base_addr;
+  unsigned long flags;
   union {
     u8  addr[(HASH_TABLE_LEN * ETH_ALEN)];
     u16 sval[(HASH_TABLE_LEN * ETH_ALEN) >> 1];
@@ -1998,19 +2001,27 @@
       set_multicast_list(dev);
     break;
 
-  case DEPCA_GET_STATS:              /* Get the driver statistics */
-    cli();
+  case DEPCA_GET_STATS: {            /* Get the driver statistics */
+    typeof(lp->pktStats) *tmp_stats =
+	    kmalloc(sizeof(lp->pktStats), GFP_KERNEL);
+    if (!tmp_stats) return -ENOMEM;
+
+    spin_lock_irqsave(&lp->lock, flags);
+    memcpy(tmp_stats, &lp->pktStats, sizeof(lp->pktStats));
+    spin_unlock_irqrestore(&lp->lock, flags);
+
     ioc->len = sizeof(lp->pktStats);
-    if (copy_to_user(ioc->data, &lp->pktStats, ioc->len))
+    if (copy_to_user(ioc->data, tmp_stats, sizeof(lp->pktStats)))
       status = -EFAULT;
-    sti();
+    kfree(tmp_stats);
     break;
+  }
 
   case DEPCA_CLR_STATS:              /* Zero out the driver statistics */
     if (!capable(CAP_NET_ADMIN)) return -EPERM;
-    cli();
+    spin_lock_irqsave(&lp->lock, flags);
     memset(&lp->pktStats, 0, sizeof(lp->pktStats));
-    sti();
+    spin_unlock_irqrestore(&lp->lock, flags);
     break;
 
   case DEPCA_GET_REG:                /* Get the DEPCA Registers */