drop_monitor: Add error code to detect duplicate state changes

Patch to add -EAGAIN error to dropwatch netlink message handling code. -EAGAIN will be returned anytime userspace attempts to transition the state of the drop monitor service to a state that its already in. That allows user space to detect this condition, so it doesn't wait for a success ACK that will never arrive. Tested successfully by me Signed-off-by: Neil Horman <[email protected]> Signed-off-by: David S. Miller <[email protected]>
csanz · Jul 20, 2010 · 4b70637 · 4b70637
1 parent d79d991
commit 4b70637
Showing 1 changed file with 8 additions and 2 deletions.
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
@@ -223,6 +223,11 @@ static int set_all_monitor_traces(int state)
 
 	spin_lock(&trace_state_lock);
 
+	if (state == trace_state) {
+		rc = -EAGAIN;
+		goto out_unlock;
+	}
+
 	switch (state) {
 	case TRACE_ON:
 		rc |= register_trace_kfree_skb(trace_kfree_skb_hit, NULL);
@@ -251,11 +256,12 @@ static int set_all_monitor_traces(int state)
 
 	if (!rc)
 		trace_state = state;
+	else
+		rc = -EINPROGRESS;
 
+out_unlock:
 	spin_unlock(&trace_state_lock);
 
-	if (rc)
-		return -EINPROGRESS;
 	return rc;
 }