Re: [PATCH 1/1] netstamp_needed shouldn't be jump_label_key

[Eric Dumazet <eric.dumazet@gmail.com>]

Le lundi 28 novembre 2011 à 21:33 +0100, Eric Dumazet a écrit :
> Le lundi 28 novembre 2011 à 21:23 +0100, igorm@etf.rs a écrit :
> > From: Igor Maravic <igorm@etf.rs>
> > 
> > Problem with setting netstamp_needed as jump_label_key is that
> > it inc/dec, functions net_enable_timestamp/net_disable_timestamp,
> > are called from interrupts.
> > 
> > That can cause DEADLOCK, because jump_label_{inc, dec} are using mutex locking,
> > that may sleep.
> > 
> > Signed-off-by: Igor Maravic <igorm@etf.rs>
> > 
> 
> Come on, we can find another way to handle this :)
> 
> Its net-next, we are allowed to try to find something better.
> 

Could you test following patch ?

Thanks

[PATCH net-next] net: dont call jump_label_dec from irq context

Igor Maravic reported an error caused by jump_label_dec() being called
from IRQ context :

 BUG: sleeping function called from invalid context at kernel/mutex.c:271
 in_atomic(): 1, irqs_disabled(): 0, pid: 0, name: swapper
 1 lock held by swapper/0:
  #0:  (&n->timer){+.-...}, at: [<ffffffff8107ce90>] call_timer_fn+0x0/0x340
 Pid: 0, comm: swapper Not tainted 3.2.0-rc2-net-next-mpls+ #1
Call Trace:
 <IRQ>  [<ffffffff8104f417>] __might_sleep+0x137/0x1f0
 [<ffffffff816b9a2f>] mutex_lock_nested+0x2f/0x370
 [<ffffffff810a89fd>] ? trace_hardirqs_off+0xd/0x10
 [<ffffffff8109a37f>] ? local_clock+0x6f/0x80
 [<ffffffff810a90a5>] ? lock_release_holdtime.part.22+0x15/0x1a0
 [<ffffffff81557929>] ? sock_def_write_space+0x59/0x160
 [<ffffffff815e936e>] ? arp_error_report+0x3e/0x90
 [<ffffffff810969cd>] atomic_dec_and_mutex_lock+0x5d/0x80
 [<ffffffff8112fc1d>] jump_label_dec+0x1d/0x50
 [<ffffffff81566525>] net_disable_timestamp+0x15/0x20
 [<ffffffff81557a75>] sock_disable_timestamp+0x45/0x50
 [<ffffffff81557b00>] __sk_free+0x80/0x200
 [<ffffffff815578d0>] ? sk_send_sigurg+0x70/0x70
 [<ffffffff815e936e>] ? arp_error_report+0x3e/0x90
 [<ffffffff81557cba>] sock_wfree+0x3a/0x70
 [<ffffffff8155c2b0>] skb_release_head_state+0x70/0x120
 [<ffffffff8155c0b6>] __kfree_skb+0x16/0x30
 [<ffffffff8155c119>] kfree_skb+0x49/0x170
 [<ffffffff815e936e>] arp_error_report+0x3e/0x90
 [<ffffffff81575bd9>] neigh_invalidate+0x89/0xc0
 [<ffffffff81578dbe>] neigh_timer_handler+0x9e/0x2a0
 [<ffffffff81578d20>] ? neigh_update+0x640/0x640
 [<ffffffff81073558>] __do_softirq+0xc8/0x3a0

Since jump_label_{inc|dec} must be called from process context only,
we must defer jump_label_dec() if net_disable_timestamp() is called
from interrupt context.

Reported-by: Igor Maravic <igorm@etf.rs>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
 net/core/dev.c                 |   23 +++++++++++++++++++++++
 net/ipv4/netfilter/ip_queue.c  |    6 ++++--
 net/ipv6/netfilter/ip6_queue.c |    5 ++++-
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 8afb244..de5266c 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1443,15 +1443,38 @@ int call_netdevice_notifiers(unsigned long val, struct net_device *dev)
 EXPORT_SYMBOL(call_netdevice_notifiers);
 
 static struct jump_label_key netstamp_needed __read_mostly;
+#ifdef HAVE_JUMP_LABEL
+/* We are not allowed to call jump_label_dec() from irq context
+ * If net_disable_timestamp() is called from irq context, defer the
+ * jump_label_dec() calls.
+ */
+static atomic_t netstamp_needed_deferred;
+#endif
 
 void net_enable_timestamp(void)
 {
+#ifdef HAVE_JUMP_LABEL
+	int deferred = atomic_xchg(&netstamp_needed_deferred, 0);
+
+	if (deferred) {
+		while (--deferred)
+			jump_label_dec(&netstamp_needed);
+		return;
+	}
+#endif
+	WARN_ON(in_interrupt());
 	jump_label_inc(&netstamp_needed);
 }
 EXPORT_SYMBOL(net_enable_timestamp);
 
 void net_disable_timestamp(void)
 {
+#ifdef HAVE_JUMP_LABEL
+	if (in_interrupt()) {
+		atomic_inc(&netstamp_needed_deferred);
+		return;
+	}
+#endif
 	jump_label_dec(&netstamp_needed);
 }
 EXPORT_SYMBOL(net_disable_timestamp);
diff --git a/net/ipv4/netfilter/ip_queue.c b/net/ipv4/netfilter/ip_queue.c
index e59aabd..a057fe6 100644
--- a/net/ipv4/netfilter/ip_queue.c
+++ b/net/ipv4/netfilter/ip_queue.c
@@ -404,6 +404,7 @@ __ipq_rcv_skb(struct sk_buff *skb)
 	int status, type, pid, flags;
 	unsigned int nlmsglen, skblen;
 	struct nlmsghdr *nlh;
+	bool enable_timestamp = false;
 
 	skblen = skb->len;
 	if (skblen < sizeof(*nlh))
@@ -441,12 +442,13 @@ __ipq_rcv_skb(struct sk_buff *skb)
 			RCV_SKB_FAIL(-EBUSY);
 		}
 	} else {
-		net_enable_timestamp();
+		enable_timestamp = true;
 		peer_pid = pid;
 	}
 
 	spin_unlock_bh(&queue_lock);
-
+	if (enable_timestamp)
+		net_enable_timestamp();
 	status = ipq_receive_peer(NLMSG_DATA(nlh), type,
 				  nlmsglen - NLMSG_LENGTH(0));
 	if (status < 0)
diff --git a/net/ipv6/netfilter/ip6_queue.c b/net/ipv6/netfilter/ip6_queue.c
index e63c397..fb80a23 100644
--- a/net/ipv6/netfilter/ip6_queue.c
+++ b/net/ipv6/netfilter/ip6_queue.c
@@ -405,6 +405,7 @@ __ipq_rcv_skb(struct sk_buff *skb)
 	int status, type, pid, flags;
 	unsigned int nlmsglen, skblen;
 	struct nlmsghdr *nlh;
+	bool enable_timestamp = false;
 
 	skblen = skb->len;
 	if (skblen < sizeof(*nlh))
@@ -442,11 +443,13 @@ __ipq_rcv_skb(struct sk_buff *skb)
 			RCV_SKB_FAIL(-EBUSY);
 		}
 	} else {
-		net_enable_timestamp();
+		enable_timestamp = true;
 		peer_pid = pid;
 	}
 
 	spin_unlock_bh(&queue_lock);
+	if (enable_timestamp)
+		net_enable_timestamp();
 
 	status = ipq_receive_peer(NLMSG_DATA(nlh), type,
 				  nlmsglen - NLMSG_LENGTH(0));