From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: locking api self-test hanging Date: Tue, 04 Mar 2008 12:30:00 -0800 (PST) Message-ID: <20080304.123000.183265831.davem@davemloft.net> References: <20080304084024.GA3980@ff.dom.local> <20080304011050.74f30dd3.akpm@linux-foundation.org> <20080304075137.6bbd285f@extreme> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: akpm@linux-foundation.org, netdev@vger.kernel.org To: shemminger@linux-foundation.org Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:33438 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1756319AbYCDUaG (ORCPT ); Tue, 4 Mar 2008 15:30:06 -0500 In-Reply-To: <20080304075137.6bbd285f@extreme> Sender: netdev-owner@vger.kernel.org List-ID: From: Stephen Hemminger Date: Tue, 4 Mar 2008 07:51:37 -0800 > On Tue, 4 Mar 2008 01:10:50 -0800 > Andrew Morton wrote: > > > That bisecting took me several hours and at the time I hoped that it would > > receive a more-than-zero response. btw. > > Mia culpa, individual tests of the netconsole when I did the patch worked. > But obviously didn't stress it enough or trigger that drop code. > > Plus, I didn't believe the bisect. At least Jarek figured it out in the end :-) I'll revert these two changesets like so: commit d9452e9f81e997cbd0c9bface8d2c2a4b064cc3e Author: David S. Miller Date: Tue Mar 4 12:28:49 2008 -0800 [NETPOLL]: Revert two bogus cleanups that broke netconsole. Based upon a report by Andrew Morton and code analysis done by Jarek Poplawski. This reverts 33f807ba0d9259e7c75c7a2ce8bd2787e5b540c7 ("[NETPOLL]: Kill NETPOLL_RX_DROP, set but never tested.") and c7b6ea24b43afb5749cb704e143df19d70e23dea ("[NETPOLL]: Don't need rx_flags."). The rx_flags did get tested for zero vs. non-zero and therefore we do need those tests and that code which sets NETPOLL_RX_DROP et al. Signed-off-by: David S. Miller diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h index a0525a1..e3d7959 100644 --- a/include/linux/netpoll.h +++ b/include/linux/netpoll.h @@ -25,6 +25,7 @@ struct netpoll { struct netpoll_info { atomic_t refcnt; + int rx_flags; spinlock_t rx_lock; struct netpoll *rx_np; /* netpoll that registered an rx_hook */ struct sk_buff_head arp_tx; /* list of arp requests to reply to */ @@ -50,12 +51,12 @@ static inline int netpoll_rx(struct sk_buff *skb) unsigned long flags; int ret = 0; - if (!npinfo || !npinfo->rx_np) + if (!npinfo || (!npinfo->rx_np && !npinfo->rx_flags)) return 0; spin_lock_irqsave(&npinfo->rx_lock, flags); - /* check rx_np again with the lock held */ - if (npinfo->rx_np && __netpoll_rx(skb)) + /* check rx_flags again with the lock held */ + if (npinfo->rx_flags && __netpoll_rx(skb)) ret = 1; spin_unlock_irqrestore(&npinfo->rx_lock, flags); diff --git a/net/core/netpoll.c b/net/core/netpoll.c index 6faa128..4b7e756 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -39,6 +39,8 @@ static struct sk_buff_head skb_pool; 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) + \ @@ -126,11 +128,13 @@ 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; } @@ -472,7 +476,7 @@ int __netpoll_rx(struct sk_buff *skb) if (skb->dev->type != ARPHRD_ETHER) goto out; - /* if receive ARP during middle of NAPI poll, then queue */ + /* check if netpoll clients need ARP */ if (skb->protocol == htons(ETH_P_ARP) && atomic_read(&trapped)) { skb_queue_tail(&npi->arp_tx, skb); @@ -534,9 +538,6 @@ 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; @@ -675,6 +676,7 @@ int netpoll_setup(struct netpoll *np) goto release; } + npinfo->rx_flags = 0; npinfo->rx_np = NULL; spin_lock_init(&npinfo->rx_lock); @@ -756,6 +758,7 @@ int netpoll_setup(struct netpoll *np) if (np->rx_hook) { spin_lock_irqsave(&npinfo->rx_lock, flags); + npinfo->rx_flags |= NETPOLL_RX_ENABLED; npinfo->rx_np = np; spin_unlock_irqrestore(&npinfo->rx_lock, flags); } @@ -797,6 +800,7 @@ void netpoll_cleanup(struct netpoll *np) if (npinfo->rx_np == np) { spin_lock_irqsave(&npinfo->rx_lock, flags); npinfo->rx_np = NULL; + npinfo->rx_flags &= ~NETPOLL_RX_ENABLED; spin_unlock_irqrestore(&npinfo->rx_lock, flags); }