[PATCH 13/27] UBUNTU: SAUCE: net/flow: remove sleeping and deferral mechanism from flow_cache_flush

[Madalin Bucur]

flow_cache_flush must not sleep as it can be called in atomic context;
removed the schedule_work as the deferred processing lead to the flow
cache gc never being actually run under heavy network load

This patch is being maintained and will eventually be merged upstream by
Freescale directly. The powerpc-e500mc flavour uses this.

Signed-off-by: Madalin Bucur <madalin.bucur at freescale.com>
Signed-off-by: Ben Collins <bcollins at ubuntu.com>
---
 net/core/flow.c |   21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/net/core/flow.c b/net/core/flow.c
index e318c7e..0b66876 100644
--- a/net/core/flow.c
+++ b/net/core/flow.c
@@ -14,7 +14,6 @@
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/smp.h>
-#include <linux/completion.h>
 #include <linux/percpu.h>
 #include <linux/bitops.h>
 #include <linux/notifier.h>
@@ -49,7 +48,6 @@ struct flow_cache_percpu {
 struct flow_flush_info {
 	struct flow_cache		*cache;
 	atomic_t			cpuleft;
-	struct completion		completion;
 };
 
 struct flow_cache {
@@ -100,7 +98,7 @@ static void flow_entry_kill(struct flow_cache_entry *fle)
 	kmem_cache_free(flow_cachep, fle);
 }
 
-static void flow_cache_gc_task(struct work_struct *work)
+static void flow_cache_gc_task(void)
 {
 	struct list_head gc_list;
 	struct flow_cache_entry *fce, *n;
@@ -113,7 +111,6 @@ static void flow_cache_gc_task(struct work_struct *work)
 	list_for_each_entry_safe(fce, n, &gc_list, u.gc_list)
 		flow_entry_kill(fce);
 }
-static DECLARE_WORK(flow_cache_gc_work, flow_cache_gc_task);
 
 static void flow_cache_queue_garbage(struct flow_cache_percpu *fcp,
 				     int deleted, struct list_head *gc_list)
@@ -123,7 +120,7 @@ static void flow_cache_queue_garbage(struct flow_cache_percpu *fcp,
 		spin_lock_bh(&flow_cache_gc_lock);
 		list_splice_tail(gc_list, &flow_cache_gc_list);
 		spin_unlock_bh(&flow_cache_gc_lock);
-		schedule_work(&flow_cache_gc_work);
+		flow_cache_gc_task();
 	}
 }
 
@@ -320,8 +317,7 @@ static void flow_cache_flush_tasklet(unsigned long data)
 
 	flow_cache_queue_garbage(fcp, deleted, &gc_list);
 
-	if (atomic_dec_and_test(&info->cpuleft))
-		complete(&info->completion);
+	atomic_dec(&info->cpuleft);
 }
 
 static void flow_cache_flush_per_cpu(void *data)
@@ -339,22 +335,23 @@ static void flow_cache_flush_per_cpu(void *data)
 void flow_cache_flush(void)
 {
 	struct flow_flush_info info;
-	static DEFINE_MUTEX(flow_flush_sem);
+	static DEFINE_SPINLOCK(flow_flush_lock);
 
 	/* Don't want cpus going down or up during this. */
 	get_online_cpus();
-	mutex_lock(&flow_flush_sem);
+	spin_lock_bh(&flow_flush_lock);
 	info.cache = &flow_cache_global;
 	atomic_set(&info.cpuleft, num_online_cpus());
-	init_completion(&info.completion);
 
 	local_bh_disable();
 	smp_call_function(flow_cache_flush_per_cpu, &info, 0);
 	flow_cache_flush_tasklet((unsigned long)&info);
 	local_bh_enable();
 
-	wait_for_completion(&info.completion);
-	mutex_unlock(&flow_flush_sem);
+	while (atomic_read(&info.cpuleft) != 0)
+		cpu_relax();
+
+	spin_unlock_bh(&flow_flush_lock);
 	put_online_cpus();
 }
 
-- 
1.7.9.5