pfinet: fix emission on the loopback device

Unlike other devices, sending packets on the loopback device causes the
netif_rx() function to be called from the net_bh worker thread. Since
the thread is already running, it can't wake itself up when calling
mark_bh(). Use a new variable to indicate when net_bh work is pending.

* glue-include/linux/interrupt.h (net_bh_raised): Declare new global
variable.
(mark_bh): Set net_bh_raised to 1 before waking up net_bh worker thread.
* loopback.c (loopback_xmit): Add comment giving details about locking.
* sched.c (net_bh_raised): Define new global variable.
(net_bh_worker): Wait for net_bh_raised to become true and reset it
before processing net_bh work.

3 files changed, 15 insertions, 1 deletions

diff --git a/pfinet/glue-include/linux/interrupt.h b/pfinet/glue-include/linux/interrupt.h
index df58d2f4..22312ba4 100644
--- a/pfinet/glue-include/linux/interrupt.h
+++ b/pfinet/glue-include/linux/interrupt.h
@@ -21,6 +21,7 @@ extern pthread_mutex_t net_bh_lock;
 
 /* See sched.c::net_bh_worker comments.  */
 extern pthread_cond_t net_bh_wakeup;
+extern int net_bh_raised;
 
 #define NET_BH	0xb00bee51
 
@@ -30,6 +31,7 @@ static inline void
 mark_bh (int bh)
 {
   assert (bh == NET_BH);
+  net_bh_raised = 1;
   pthread_cond_broadcast (&net_bh_wakeup);
 }
 
diff --git a/pfinet/loopback.c b/pfinet/loopback.c
index 068cf3c8..e15e4265 100644
--- a/pfinet/loopback.c
+++ b/pfinet/loopback.c
@@ -71,6 +71,13 @@ static int loopback_xmit(struct sk_buff *skb, struct device *dev)
 #ifndef LOOPBACK_MUST_CHECKSUM
 	skb->ip_summed = CHECKSUM_UNNECESSARY;
 #endif
+
+	/*
+	 *	Calling netif_rx() requires locking net_bh_lock, which
+	 *	has already been done since this function is called by
+	 *	the net_bh worker thread.
+	 */
+
 	netif_rx(skb);
 
 	stats->rx_bytes+=skb->len;
diff --git a/pfinet/sched.c b/pfinet/sched.c
index 89927741..af03ab49 100644
--- a/pfinet/sched.c
+++ b/pfinet/sched.c
@@ -26,6 +26,7 @@
 pthread_mutex_t global_lock = PTHREAD_MUTEX_INITIALIZER;
 pthread_mutex_t net_bh_lock = PTHREAD_MUTEX_INITIALIZER;
 pthread_cond_t net_bh_wakeup = PTHREAD_COND_INITIALIZER;
+int net_bh_raised = 0;
 
 struct task_struct current_contents; /* zeros are right default values */
 
@@ -61,7 +62,11 @@ net_bh_worker (void *arg)
   pthread_mutex_lock (&net_bh_lock);
   while (1)
     {
-      pthread_cond_wait (&net_bh_wakeup, &net_bh_lock);
+      while (!net_bh_raised)
+        pthread_cond_wait (&net_bh_wakeup, &net_bh_lock);
+
+      net_bh_raised = 0;
+
       pthread_mutex_lock (&global_lock);
       net_bh ();
       pthread_mutex_unlock (&global_lock);