Based on http://patchwork.ozlabs.org/patch/132353/

diff --git a/net/core/flow.c b/net/core/flow.c
index 8ae42de..e318c7e 100644
--- a/net/core/flow.c
+++ b/net/core/flow.c
@@ -358,6 +358,18 @@ void flow_cache_flush(void)
 	put_online_cpus();
 }
 
+static void flow_cache_flush_task(struct work_struct *work)
+{
+	flow_cache_flush();
+}
+
+static DECLARE_WORK(flow_cache_flush_work, flow_cache_flush_task);
+
+void flow_cache_flush_deferred(void)
+{
+	schedule_work(&flow_cache_flush_work);
+}
+
 static int __cpuinit flow_cache_cpu_prepare(struct flow_cache *fc, int cpu)
 {
 	struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 2118d64..9049a5c 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -2276,8 +2276,6 @@ static void __xfrm_garbage_collect(struct net *net)
 {
 	struct dst_entry *head, *next;
 
-	flow_cache_flush();
-
 	spin_lock_bh(&xfrm_policy_sk_bundle_lock);
 	head = xfrm_policy_sk_bundles;
 	xfrm_policy_sk_bundles = NULL;
@@ -2290,6 +2288,18 @@ static void __xfrm_garbage_collect(struct net *net)
 	}
 }
 
+static void xfrm_garbage_collect(struct net *net)
+{
+	flow_cache_flush();
+	__xfrm_garbage_collect(net);
+}
+
+static void xfrm_garbage_collect_deferred(struct net *net)
+{
+	flow_cache_flush_deferred();
+	__xfrm_garbage_collect(net);
+}
+
 static void xfrm_init_pmtu(struct dst_entry *dst)
 {
 	do {
@@ -2422,7 +2432,7 @@ int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo)
 		if (likely(dst_ops->neigh_lookup == NULL))
 			dst_ops->neigh_lookup = xfrm_neigh_lookup;
 		if (likely(afinfo->garbage_collect == NULL))
-			afinfo->garbage_collect = __xfrm_garbage_collect;
+			afinfo->garbage_collect = xfrm_garbage_collect_deferred;
 		xfrm_policy_afinfo[afinfo->family] = afinfo;
 	}
 	write_unlock_bh(&xfrm_policy_afinfo_lock);
@@ -2516,7 +2526,7 @@ static int xfrm_dev_event(struct notifier_block *this, unsigned long event, void
 
 	switch (event) {
 	case NETDEV_DOWN:
-		__xfrm_garbage_collect(dev_net(dev));
+		xfrm_garbage_collect(dev_net(dev));
 	}
 	return NOTIFY_DONE;
 }
--- ./include/net/flow.h.orig
+++ ./include/net/flow.h
@@ -207,6 +207,7 @@
 		u8 dir, flow_resolve_t resolver, void *ctx);
 
 extern void flow_cache_flush(void);
+extern void flow_cache_flush_deferred(void);
 extern atomic_unchecked_t flow_cache_genid;
 
 #endif