Re: [PATCH]: 8139cp: Don't blindly enable interrupts in cp_start_xmit
Chris Lalancette <[EMAIL PROTECTED]> : [...] > Thanks for the comments. While the patch you sent will help, there are > still other places that will have problems. For example, in netpoll_send_skb, > we call local_irq_save(flags), then call dev->hard_start_xmit(), and then call > local_irq_restore(flags). This is a similar situation to what I described > above; we will re-enable interrupts in cp_start_xmit(), when netpoll_send_skb > doesn't expect that, and will probably run into issues. > Is there a problem with changing cp_start_xmit to use the > spin_lock_irqsave(), besides the extra instructions it needs? No. Given the history of locking in netpoll and the content of Documentation/networking/netdevices.txt, asking Herbert which rule(s) the code is supposed to follow seemed safer to me. You can forget my patch. Please resend your patch inlined to Jeff as described in http://linux.yyz.us/patch-format.html. -- Ueimor - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH]: 8139cp: Don't blindly enable interrupts in cp_start_xmit
Francois Romieu wrote: > Chris Lalancette <[EMAIL PROTECTED]> : > [...] > >> Similar to this commit: >> >>http://kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=d15e9c4d9a75702b30e00cdf95c71c88e3f3f51e >> >>It's not safe in cp_start_xmit to blindly call spin_lock_irq and then >>spin_unlock_irq, since it may very well be the case that cp_start_xmit >>was called with interrupts already disabled (I came across this bug in >>the context of netdump in RedHat kernels, but the same issue holds, for >>example, in netconsole). Therefore, replace all instances of spin_lock_irq >>and spin_unlock_irq with spin_lock_irqsave and spin_unlock_irqrestore, >>respectively, in cp_start_xmit(). I tested this against a fully-virtualized >>Xen guest, which happens to use the 8139cp driver to talk to the emulated >>hardware. I don't have a real piece of 8139cp hardware to test on, so >>someone else will have to do that. > > > (message reformated to fit in 80 columns, please fix your mailer) > > As I understand http://lkml.org/lkml/2006/12/12/239, something like the > patch below should had been sent instead. Herbert, ack/nak ? > Francois, Thanks for the comments. While the patch you sent will help, there are still other places that will have problems. For example, in netpoll_send_skb, we call local_irq_save(flags), then call dev->hard_start_xmit(), and then call local_irq_restore(flags). This is a similar situation to what I described above; we will re-enable interrupts in cp_start_xmit(), when netpoll_send_skb doesn't expect that, and will probably run into issues. Is there a problem with changing cp_start_xmit to use the spin_lock_irqsave(), besides the extra instructions it needs? Thanks, Chris Lalancette - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH]: 8139cp: Don't blindly enable interrupts in cp_start_xmit
On Mon, Jan 15, 2007 at 08:56:35PM +0100, Francois Romieu wrote:
>
> As I understand http://lkml.org/lkml/2006/12/12/239, something like the
> patch below should had been sent instead. Herbert, ack/nak ?
Sorry, what I said in that thread is in error. Netpoll may
unfortunately call the transmit routine with IRQs off. So
the drivers can't currently use spin_lock_irq and must save
the current flags instead.
Cheers,
--
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Email: Herbert Xu ~{PmV>HI~} <[EMAIL PROTECTED]>
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Re: [PATCH]: 8139cp: Don't blindly enable interrupts in cp_start_xmit
Chris Lalancette <[EMAIL PROTECTED]> :
[...]
> Similar to this commit:
>
> http://kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=d15e9c4d9a75702b30e00cdf95c71c88e3f3f51e
>
> It's not safe in cp_start_xmit to blindly call spin_lock_irq and then
> spin_unlock_irq, since it may very well be the case that cp_start_xmit
> was called with interrupts already disabled (I came across this bug in
> the context of netdump in RedHat kernels, but the same issue holds, for
> example, in netconsole). Therefore, replace all instances of spin_lock_irq
> and spin_unlock_irq with spin_lock_irqsave and spin_unlock_irqrestore,
> respectively, in cp_start_xmit(). I tested this against a fully-virtualized
> Xen guest, which happens to use the 8139cp driver to talk to the emulated
> hardware. I don't have a real piece of 8139cp hardware to test on, so
> someone else will have to do that.
(message reformated to fit in 80 columns, please fix your mailer)
As I understand http://lkml.org/lkml/2006/12/12/239, something like the
patch below should had been sent instead. Herbert, ack/nak ?
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 823215d..ff95641 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -55,7 +55,6 @@ static void queue_process(struct work_struct *work)
struct netpoll_info *npinfo =
container_of(work, struct netpoll_info, tx_work.work);
struct sk_buff *skb;
- unsigned long flags;
while ((skb = skb_dequeue(&npinfo->txq))) {
struct net_device *dev = skb->dev;
@@ -65,19 +64,16 @@ static void queue_process(struct work_struct *work)
continue;
}
- local_irq_save(flags);
netif_tx_lock(dev);
if (netif_queue_stopped(dev) ||
dev->hard_start_xmit(skb, dev) != NETDEV_TX_OK) {
skb_queue_head(&npinfo->txq, skb);
netif_tx_unlock(dev);
- local_irq_restore(flags);
schedule_delayed_work(&npinfo->tx_work, HZ/10);
return;
}
netif_tx_unlock(dev);
- local_irq_restore(flags);
}
}
-
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[PATCH]: 8139cp: Don't blindly enable interrupts in cp_start_xmit
(trying again, this time to the correct maintainer)
All,
Similar to this commit:
http://kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=d15e9c4d9a75702b30e00cdf95c71c88e3f3f51e
It's not safe in cp_start_xmit to blindly call spin_lock_irq and then
spin_unlock_irq, since it may very well be the case that cp_start_xmit was
called with interrupts already disabled (I came across this bug in the context
of netdump in RedHat kernels, but the same issue holds, for example, in
netconsole). Therefore, replace all instances of spin_lock_irq and
spin_unlock_irq with spin_lock_irqsave and spin_unlock_irqrestore,
respectively, in cp_start_xmit(). I tested this against a fully-virtualized
Xen guest, which happens to use the 8139cp driver to talk to the emulated
hardware. I don't have a real piece of 8139cp hardware to test on, so someone
else will have to do that.
Signed-off-by: Chris Lalancette <[EMAIL PROTECTED]>
diff --git a/drivers/net/8139cp.c b/drivers/net/8139cp.c
index e2cb19b..6f93a76 100644
--- a/drivers/net/8139cp.c
+++ b/drivers/net/8139cp.c
@@ -765,17 +765,18 @@ static int cp_start_xmit (struct sk_buff *skb, struct net_device *dev)
struct cp_private *cp = netdev_priv(dev);
unsigned entry;
u32 eor, flags;
+ unsigned long intr_flags;
#if CP_VLAN_TAG_USED
u32 vlan_tag = 0;
#endif
int mss = 0;
- spin_lock_irq(&cp->lock);
+ spin_lock_irqsave(&cp->lock, intr_flags);
/* This is a hard error, log it. */
if (TX_BUFFS_AVAIL(cp) <= (skb_shinfo(skb)->nr_frags + 1)) {
netif_stop_queue(dev);
- spin_unlock_irq(&cp->lock);
+ spin_unlock_irqrestore(&cp->lock, intr_flags);
printk(KERN_ERR PFX "%s: BUG! Tx Ring full when queue awake!\n",
dev->name);
return 1;
@@ -908,7 +909,7 @@ static int cp_start_xmit (struct sk_buff *skb, struct net_device *dev)
if (TX_BUFFS_AVAIL(cp) <= (MAX_SKB_FRAGS + 1))
netif_stop_queue(dev);
- spin_unlock_irq(&cp->lock);
+ spin_unlock_irqrestore(&cp->lock, intr_flags);
cpw8(TxPoll, NormalTxPoll);
dev->trans_start = jiffies;
[PATCH]: 8139cp: Don't blindly enable interrupts in cp_start_xmit
All,
Similar to this commit:
http://kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=d15e9c4d9a75702b30e00cdf95c71c88e3f3f51e
It's not safe in cp_start_xmit to blindly call spin_lock_irq and then
spin_unlock_irq, since it may very well be the case that cp_start_xmit was
called with interrupts already disabled (I came across this bug in the context
of netdump in RedHat kernels, but the same issue holds, for example, in
netconsole). Therefore, replace all instances of spin_lock_irq and
spin_unlock_irq with spin_lock_irqsave and spin_unlock_irqrestore,
respectively, in cp_start_xmit(). I tested this against a fully-virtualized
Xen guest, which happens to use the 8139cp driver to talk to the emulated
hardware. I don't have a real piece of 8139cp hardware to test on, so someone
else will have to do that.
Signed-off-by: Chris Lalancette <[EMAIL PROTECTED]>
diff --git a/drivers/net/8139cp.c b/drivers/net/8139cp.c
index e2cb19b..6f93a76 100644
--- a/drivers/net/8139cp.c
+++ b/drivers/net/8139cp.c
@@ -765,17 +765,18 @@ static int cp_start_xmit (struct sk_buff *skb, struct net_device *dev)
struct cp_private *cp = netdev_priv(dev);
unsigned entry;
u32 eor, flags;
+ unsigned long intr_flags;
#if CP_VLAN_TAG_USED
u32 vlan_tag = 0;
#endif
int mss = 0;
- spin_lock_irq(&cp->lock);
+ spin_lock_irqsave(&cp->lock, intr_flags);
/* This is a hard error, log it. */
if (TX_BUFFS_AVAIL(cp) <= (skb_shinfo(skb)->nr_frags + 1)) {
netif_stop_queue(dev);
- spin_unlock_irq(&cp->lock);
+ spin_unlock_irqrestore(&cp->lock, intr_flags);
printk(KERN_ERR PFX "%s: BUG! Tx Ring full when queue awake!\n",
dev->name);
return 1;
@@ -908,7 +909,7 @@ static int cp_start_xmit (struct sk_buff *skb, struct net_device *dev)
if (TX_BUFFS_AVAIL(cp) <= (MAX_SKB_FRAGS + 1))
netif_stop_queue(dev);
- spin_unlock_irq(&cp->lock);
+ spin_unlock_irqrestore(&cp->lock, intr_flags);
cpw8(TxPoll, NormalTxPoll);
dev->trans_start = jiffies;
