[openib-general] [PATCH] cm: randomize starting local CM ID

[Sean Hefty]

Eric,

Can you try running with this patch installed?  This should decrease
the chances that a REQ will be seen as an old duplicate, rather than
a new request.

Signed-off-by: Sean Hefty <sean.hefty at intel.com>
---
Index: cm.c
===================================================================
--- cm.c	(revision 8647)
+++ cm.c	(working copy)
@@ -42,6 +42,7 @@
 #include <linux/interrupt.h>
 #include <linux/pci.h>
 #include <linux/rbtree.h>
+#include <linux/random.h>
 #include <linux/spinlock.h>
 #include <linux/workqueue.h>
 
@@ -73,6 +74,7 @@ static struct ib_cm {
 	struct rb_root remote_id_table;
 	struct rb_root remote_sidr_table;
 	struct idr local_id_table;
+	int next_id;
 	struct workqueue_struct *wq;
 } cm;
 
@@ -301,11 +303,11 @@ static int cm_alloc_id(struct cm_id_priv
 {
 	unsigned long flags;
 	int ret;
-	static int next_id;
 
 	do {
 		spin_lock_irqsave(&cm.lock, flags);
-		ret = idr_get_new_above(&cm.local_id_table, cm_id_priv, next_id++,
+		ret = idr_get_new_above(&cm.local_id_table, cm_id_priv,
+					cm.next_id++,
 					(__force int *) &cm_id_priv->id.local_id);
 		spin_unlock_irqrestore(&cm.lock, flags);
 	} while( (ret == -EAGAIN) && idr_pre_get(&cm.local_id_table, GFP_KERNEL) );
@@ -3390,6 +3392,7 @@ static int __init ib_cm_init(void)
 	cm.remote_id_table = RB_ROOT;
 	cm.remote_qp_table = RB_ROOT;
 	cm.remote_sidr_table = RB_ROOT;
+	get_random_bytes(&cm.next_id, sizeof cm.next_id);
 	idr_init(&cm.local_id_table);
 	idr_pre_get(&cm.local_id_table, GFP_KERNEL);