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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>
This commit is contained in:
Neil Horman 2010-07-20 04:52:09 +00:00 committed by David S. Miller
parent d79d991379
commit 4b706372f1
1 changed files with 8 additions and 2 deletions
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10
net/core/drop_monitor.c
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@ -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;
}