Messages in this thread Patch in this message | | | Date | Tue, 4 Mar 2008 01:10:50 -0800 | From | Andrew Morton <> | Subject | Re: locking api self-test hanging |
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On Tue, 4 Mar 2008 08:40:24 +0000 Jarek Poplawski <jarkao2@gmail.com> wrote:
> On 04-03-2008 06:05, Andrew Morton wrote: > ... > >>>> And I've fully bisected this hang twice and both times came up with > >>>> > >>>> commit 33f807ba0d9259e7c75c7a2ce8bd2787e5b540c7 > >>>> Author: Stephen Hemminger <shemminger@linux-foundation.org> > >>>> Date: Mon Nov 19 19:24:52 2007 -0800 > >>>> > >>>> [NETPOLL]: Kill NETPOLL_RX_DROP, set but never tested. > >>>> > >>>> which is stupid because that patch doesn't do anything. > > ...or maybe apparently doesn't do anything? > > @@ -128,13 +127,11 @@ static int poll_one_napi(struct netpoll_info *npinfo, > if (!test_bit(NAPI_STATE_SCHED, &napi->state)) > return budget; > > - npinfo->rx_flags |= NETPOLL_RX_DROP; > > > But in a next patch we can see: > > @@ -51,12 +50,12 @@ static inline int netpoll_rx(struct sk_buff *skb) > unsigned long flags; > int ret = 0; > > - if (!npinfo || (!npinfo->rx_np && !npinfo->rx_flags)) > + if (!npinfo || !npinfo->rx_np) > > So, it seems rx_flags could have been tested here for NETPOLL_RX_DROP > yet? >
Oh damn. I bisected this three times and the second two times both landed on this:
commit 33f807ba0d9259e7c75c7a2ce8bd2787e5b540c7 Author: Stephen Hemminger <shemminger@linux-foundation.org> Date: Mon Nov 19 19:24:52 2007 -0800
[NETPOLL]: Kill NETPOLL_RX_DROP, set but never tested. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/netpoll.c b/net/core/netpoll.c index cf6acd3..9e3aea0 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -40,7 +40,6 @@ static atomic_t trapped; #define USEC_PER_POLL 50 #define NETPOLL_RX_ENABLED 1 -#define NETPOLL_RX_DROP 2 #define MAX_SKB_SIZE \ (MAX_UDP_CHUNK + sizeof(struct udphdr) + \ @@ -128,13 +127,11 @@ static int poll_one_napi(struct netpoll_info *npinfo, if (!test_bit(NAPI_STATE_SCHED, &napi->state)) return budget; - npinfo->rx_flags |= NETPOLL_RX_DROP; atomic_inc(&trapped); work = napi->poll(napi, budget); atomic_dec(&trapped); - npinfo->rx_flags &= ~NETPOLL_RX_DROP; return budget - work; } @@ -475,7 +472,7 @@ int __netpoll_rx(struct sk_buff *skb) if (skb->dev->type != ARPHRD_ETHER) goto out; - /* check if netpoll clients need ARP */ + /* if receive ARP during middle of NAPI poll, then queue */ if (skb->protocol == htons(ETH_P_ARP) && atomic_read(&trapped)) { skb_queue_tail(&npi->arp_tx, skb); @@ -537,6 +534,9 @@ int __netpoll_rx(struct sk_buff *skb) return 1; out: + /* If packet received while already in poll then just + * silently drop. + */ if (atomic_read(&trapped)) { kfree_skb(skb); return 1; and I stupidly assumed that it couldn't be this commit because it was a no-op. I didn't think to look for an _impicit_ test of NETPOLL_RX_DROP such as the one above. That's pretty poor style IMO :(
That bisecting took me several hours and at the time I hoped that it would receive a more-than-zero response. btw.
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