On Tuesday 10 July 2007 00:27, David Miller wrote:
> I'm happy to entertain this kind of solution, but we really
> need to first have an interface to change multiple bits
> at a time in one atomic operation, because by itself this
> patch doubles the number of atomices we do when starting
> a NAPI poll.
Understood. How about the patch below? It takes a similar
approach, but it puts the onus on the netpoll code
path rather than the general NAPI case.
Olaf
--------------
From: Olaf Kirch <[EMAIL PROTECTED]>
Keep netpoll/poll_napi from messing with the poll_list.
Only net_rx_action is allowed to manipulate the list.
Signed-off-by: Olaf Kirch <[EMAIL PROTECTED]>
---
include/linux/netdevice.h | 10 ++++++++++
net/core/netpoll.c | 8 ++++++++
2 files changed, 18 insertions(+)
Index: iscsi-2.6/include/linux/netdevice.h
===================================================================
--- iscsi-2.6.orig/include/linux/netdevice.h
+++ iscsi-2.6/include/linux/netdevice.h
@@ -248,6 +248,8 @@ enum netdev_state_t
__LINK_STATE_LINKWATCH_PENDING,
__LINK_STATE_DORMANT,
__LINK_STATE_QDISC_RUNNING,
+ /* Set by the netpoll NAPI code */
+ __LINK_STATE_POLL_LIST_FROZEN,
};
@@ -919,6 +921,14 @@ static inline void netif_rx_complete(str
{
unsigned long flags;
+#ifdef CONFIG_NETPOLL
+ /* Prevent race with netpoll - yes, this is a kludge.
+ * But at least it doesn't penalize the non-netpoll
+ * code path. */
+ if (test_bit(__LINK_STATE_POLL_LIST_FROZEN, &dev->state))
+ return;
+#endif
+
local_irq_save(flags);
BUG_ON(!test_bit(__LINK_STATE_RX_SCHED, &dev->state));
list_del(&dev->poll_list);
Index: iscsi-2.6/net/core/netpoll.c
===================================================================
--- iscsi-2.6.orig/net/core/netpoll.c
+++ iscsi-2.6/net/core/netpoll.c
@@ -123,6 +123,13 @@ static void poll_napi(struct netpoll *np
if (test_bit(__LINK_STATE_RX_SCHED, &np->dev->state) &&
npinfo->poll_owner != smp_processor_id() &&
spin_trylock(&npinfo->poll_lock)) {
+ /* When calling dev->poll from poll_napi, we may end up in
+ * netif_rx_complete. However, only the CPU to which the
+ * device was queued is allowed to remove it from poll_list.
+ * Setting POLL_LIST_FROZEN tells netif_rx_complete
+ * to leave the NAPI state alone.
+ */
+ set_bit(__LINK_STATE_POLL_LIST_FROZEN, &np->dev->state);
npinfo->rx_flags |= NETPOLL_RX_DROP;
atomic_inc(&trapped);
@@ -130,6 +137,7 @@ static void poll_napi(struct netpoll *np
atomic_dec(&trapped);
npinfo->rx_flags &= ~NETPOLL_RX_DROP;
+ clear_bit(__LINK_STATE_POLL_LIST_FROZEN, &np->dev->state);
spin_unlock(&npinfo->poll_lock);
}
}
--
Olaf Kirch | --- o --- Nous sommes du soleil we love when we play
[EMAIL PROTECTED] | / | \ sol.dhoop.naytheet.ah kin.ir.samse.qurax
-
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
