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authorNeil Horman <nhorman@tuxdriver.com>2012-05-17 10:04:00 +0000
committerDavid S. Miller <davem@davemloft.net>2012-05-17 16:09:07 -0400
commitcad456d5abbb6307be7a658d701bc44ca689e906 (patch)
tree116ce24c03c83876692e79ee9436dda976f86d84
parenta1c7fff7e18f59e684e07b0f9a770561cd39f395 (diff)
downloadlinux-cad456d5abbb6307be7a658d701bc44ca689e906.tar.gz
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>
-rw-r--r--net/Kconfig2
-rw-r--r--net/core/drop_monitor.c46
2 files changed, 45 insertions, 3 deletions
diff --git a/net/Kconfig b/net/Kconfig
index 4c06c7c513a..da128235930 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
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index eca00a96bcf..3252e7e0a00 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -24,6 +24,7 @@
#include <linux/timer.h>
#include <linux/bitops.h>
#include <linux/slab.h>
+#include <linux/module.h>
#include <net/genetlink.h>
#include <net/netevent.h>
@@ -263,9 +264,15 @@ static int set_all_monitor_traces(int state)
switch (state) {
case TRACE_ON:
+ if (!try_module_get(THIS_MODULE)) {
+ rc = -ENODEV;
+ break;
+ }
+
rc |= register_trace_kfree_skb(trace_kfree_skb_hit, NULL);
rc |= register_trace_napi_poll(trace_napi_poll_hit, NULL);
break;
+
case TRACE_OFF:
rc |= unregister_trace_kfree_skb(trace_kfree_skb_hit, NULL);
rc |= unregister_trace_napi_poll(trace_napi_poll_hit, NULL);
@@ -281,6 +288,9 @@ static int set_all_monitor_traces(int state)
kfree_rcu(new_stat, rcu);
}
}
+
+ module_put(THIS_MODULE);
+
break;
default:
rc = 1;
@@ -406,7 +416,7 @@ static int __init init_net_drop_monitor(void)
rc = 0;
- for_each_present_cpu(cpu) {
+ for_each_possible_cpu(cpu) {
data = &per_cpu(dm_cpu_data, cpu);
data->cpu = cpu;
INIT_WORK(&data->dm_alert_work, send_dm_alert);
@@ -425,4 +435,36 @@ out:
return rc;
}
-late_initcall(init_net_drop_monitor);
+static void exit_net_drop_monitor(void)
+{
+ struct per_cpu_dm_data *data;
+ int cpu;
+
+ BUG_ON(unregister_netdevice_notifier(&dropmon_net_notifier));
+
+ /*
+ * Because of the module_get/put we do in the trace state change path
+ * we are guarnateed not to have any current users when we get here
+ * all we need to do is make sure that we don't have any running timers
+ * or pending schedule calls
+ */
+
+ for_each_possible_cpu(cpu) {
+ data = &per_cpu(dm_cpu_data, cpu);
+ del_timer_sync(&data->send_timer);
+ cancel_work_sync(&data->dm_alert_work);
+ /*
+ * At this point, we should have exclusive access
+ * to this struct and can free the skb inside it
+ */
+ kfree_skb(data->skb);
+ }
+
+ BUG_ON(genl_unregister_family(&net_drop_monitor_family));
+}
+
+module_init(init_net_drop_monitor);
+module_exit(exit_net_drop_monitor);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");