drop_monitor: convert to modular building

When I first wrote drop monitor I wrote it to just build monolithically.  There
is no reason it can't be built modularly as well, so lets give it that
flexibiity.

I've tested this by building it as both a module and monolithically, and it
seems to work quite well

Change notes:

v2)
* fixed for_each_present_cpu loops to be more correct as per Eric D.
* Converted exit path failures to BUG_ON as per Ben H.

v3)
* Converted del_timer to del_timer_sync to close race noted by Ben H.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: Ben Hutchings <bhutchings@solarflare.com>
Reviewed-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/Kconfig b/net/Kconfig
index 4c06c7c513a4..da1282359303 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -296,7 +296,7 @@ config NET_TCPPROBE
         module will be called tcp_probe.
 
 config NET_DROP_MONITOR
-        boolean "Network packet drop alerting service"
+        tristate "Network packet drop alerting service"
         depends on INET && EXPERIMENTAL && TRACEPOINTS
         ---help---
         This feature provides an alerting service to userspace in the