[B.A.T.M.A.N.] [PATCH v2 1/7] batman-adv: tp_meter - prevent concurrent tp_meter sessions by using workqueue

Marek Lindner
2018-05-18T01:47:48Z

From: Antonio Quartulli <a@unstable.cc>

To ensure that no more than one tp_meter session runs at the
same time, use an ordered workqueue instead of spawning
one kthread per session.

Signed-off-by: Antonio Quartulli <a@unstable.cc>
---
net/batman-adv/main.c | 10 ++++-
net/batman-adv/tp_meter.c | 77 +++++++++++++++++++--------------------
net/batman-adv/tp_meter.h | 3 +-
net/batman-adv/types.h | 3 ++
4 files changed, 50 insertions(+), 43 deletions(-)

diff --git a/net/batman-adv/main.c b/net/batman-adv/main.c
index 69c0d85b..cd3f1924 100644
--- a/net/batman-adv/main.c
+++ b/net/batman-adv/main.c
@@ -91,6 +91,10 @@ static int __init batadv_init(void)
if (ret < 0)
return ret;

+ ret = batadv_tp_meter_init();
+ if (ret < 0)
+ goto err_tp_meter;
+
INIT_LIST_HEAD(&batadv_hardif_list);
batadv_algo_init();

@@ -99,7 +103,6 @@ static int __init batadv_init(void)
batadv_v_init();
batadv_iv_init();
batadv_nc_init();
- batadv_tp_meter_init();

batadv_event_workqueue = create_singlethread_workqueue("bat_events");
if (!batadv_event_workqueue)
@@ -118,9 +121,11 @@ static int __init batadv_init(void)
return 0;

err_create_wq:
+ batadv_tp_meter_destroy();
+err_tp_meter:
batadv_tt_cache_destroy();

- return -ENOMEM;
+ return ret;
}

static void __exit batadv_exit(void)
@@ -138,6 +143,7 @@ static void __exit batadv_exit(void)
rcu_barrier();

batadv_tt_cache_destroy();
+ batadv_tp_meter_destroy();
}

/**
diff --git a/net/batman-adv/tp_meter.c b/net/batman-adv/tp_meter.c
index 11520de9..c0d27f7d 100644
--- a/net/batman-adv/tp_meter.c
+++ b/net/batman-adv/tp_meter.c
@@ -32,7 +32,6 @@
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/kref.h>
-#include <linux/kthread.h>
#include <linux/list.h>
#include <linux/netdevice.h>
#include <linux/param.h>
@@ -97,6 +96,9 @@

static u8 batadv_tp_prerandom[4096] __read_mostly;

+/* ordered work queue */
+static struct workqueue_struct *batadv_tp_meter_queue;
+
/**
* batadv_tp_session_cookie() - generate session cookie based on session ids
* @session: TP session identifier
@@ -808,19 +810,22 @@ static int batadv_tp_wait_available(struct batadv_tp_vars *tp_vars, size_t plen)

/**
* batadv_tp_send() - main sending thread of a tp meter session
- * @arg: address of the related tp_vars
+ * @work: delayed work reference of the related tp_vars
*
* Return: nothing, this function never returns
*/
-static int batadv_tp_send(void *arg)
+static void batadv_tp_send(struct work_struct *work)
{
- struct batadv_tp_vars *tp_vars = arg;
- struct batadv_priv *bat_priv = tp_vars->bat_priv;
struct batadv_hard_iface *primary_if = NULL;
struct batadv_orig_node *orig_node = NULL;
+ struct batadv_tp_vars *tp_vars;
size_t payload_len, packet_len;
+ struct batadv_priv *bat_priv;
int err = 0;

+ tp_vars = container_of(work, struct batadv_tp_vars, test_work);
+ bat_priv = tp_vars->bat_priv;
+
if (unlikely(tp_vars->role != BATADV_TP_SENDER)) {
err = BATADV_TP_REASON_DST_UNREACHABLE;
tp_vars->reason = err;
@@ -901,40 +906,17 @@ static int batadv_tp_send(void *arg)
batadv_tp_sender_cleanup(bat_priv, tp_vars);

batadv_tp_vars_put(tp_vars);
-
- do_exit(0);
}

/**
- * batadv_tp_start_kthread() - start new thread which manages the tp meter
- * sender
+ * batadv_tp_start_work - start new thread which manages the tp meter sender
* @tp_vars: the private data of the current TP meter session
*/
-static void batadv_tp_start_kthread(struct batadv_tp_vars *tp_vars)
+static void batadv_tp_start_work(struct batadv_tp_vars *tp_vars)
{
- struct task_struct *kthread;
- struct batadv_priv *bat_priv = tp_vars->bat_priv;
- u32 session_cookie;
-
- kref_get(&tp_vars->refcount);
- kthread = kthread_create(batadv_tp_send, tp_vars, "kbatadv_tp_meter");
- if (IS_ERR(kthread)) {
- session_cookie = batadv_tp_session_cookie(tp_vars->session,
- tp_vars->icmp_uid);
- pr_err("batadv: cannot create tp meter kthread\n");
- batadv_tp_batctl_error_notify(BATADV_TP_REASON_MEMORY_ERROR,
- tp_vars->other_end,
- bat_priv, session_cookie);
-
- /* drop reserved reference for kthread */
- batadv_tp_vars_put(tp_vars);
-
- /* cleanup of failed tp meter variables */
- batadv_tp_sender_cleanup(bat_priv, tp_vars);
- return;
- }
-
- wake_up_process(kthread);
+ /* init work item that will actually execute the test and schedule it */
+ INIT_WORK(&tp_vars->test_work, batadv_tp_send);
+ queue_work(batadv_tp_meter_queue, &tp_vars->test_work);
}

/**
@@ -1053,13 +1035,10 @@ void batadv_tp_start(struct batadv_priv *bat_priv, const u8 *dst,
/* init work item for finished tp tests */
INIT_DELAYED_WORK(&tp_vars->finish_work, batadv_tp_sender_finish);

- /* start tp kthread. This way the write() call issued from userspace can
- * happily return and avoid to block
+ /* schedule the tp worker. This way the write() call issued from
+ * userspace can happily return and avoid to block
*/
- batadv_tp_start_kthread(tp_vars);
-
- /* don't return reference to new tp_vars */
- batadv_tp_vars_put(tp_vars);
+ batadv_tp_start_work(tp_vars);
}

/**
@@ -1498,8 +1477,26 @@ void batadv_tp_meter_recv(struct batadv_priv *bat_priv, struct sk_buff *skb)

/**
* batadv_tp_meter_init() - initialize global tp_meter structures
+ *
+ * Return: 0 on success, -ENOMEM if the tp_meter queue allocation fails
*/
-void __init batadv_tp_meter_init(void)
+int __init batadv_tp_meter_init(void)
{
get_random_bytes(batadv_tp_prerandom, sizeof(batadv_tp_prerandom));
+
+ batadv_tp_meter_queue = alloc_ordered_workqueue("bat_tp_meter", 0);
+ if (!batadv_tp_meter_queue)
+ return -ENOMEM;
+
+ return 0;
+}
+
+/**
+ * batadv_tp_meter_destroy() - destroy tp meter memory allocations
+ */
+void batadv_tp_meter_destroy(void)
+{
+ flush_workqueue(batadv_tp_meter_queue);
+ destroy_workqueue(batadv_tp_meter_queue);
+ batadv_tp_meter_queue = NULL;
}
diff --git a/net/batman-adv/tp_meter.h b/net/batman-adv/tp_meter.h
index 68e60097..ab0bde26 100644
--- a/net/batman-adv/tp_meter.h
+++ b/net/batman-adv/tp_meter.h
@@ -25,7 +25,8 @@

struct sk_buff;

-void batadv_tp_meter_init(void);
+int batadv_tp_meter_init(void);
+void batadv_tp_meter_destroy(void);
void batadv_tp_start(struct batadv_priv *bat_priv, const u8 *dst,
u32 test_length, u32 *cookie);
void batadv_tp_stop(struct batadv_priv *bat_priv, const u8 *dst,
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 360357f8..baae5206 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -1354,6 +1354,9 @@ struct batadv_tp_vars {
/** @finish_work: work item for the finishing procedure */
struct delayed_work finish_work;

+ /** @test_work: work item for the test process */
+ struct work_struct test_work;
+
/** @test_length: test length in milliseconds */
u32 test_length;

--
2.17.0