From 4b706372f18de53970e4c6887a96459590fef80a Mon Sep 17 00:00:00 2001
From: Neil Horman <nhorman@tuxdriver.com>
Date: Tue, 20 Jul 2010 04:52:09 +0000
Subject: [PATCH] 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 <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/core/drop_monitor.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index ad41529fb60f..646ef3bc7200 100644
--- 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;
}
--
GitLab