[hurd] 01/98: pfinet: fix emission on the loopback device

[Samuel Thibault]

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sthibault pushed a commit to branch upstream
in repository hurd.

commit 218cae5a714342b5d82a5b004d58f0a9ebbbfe5e
Author: Richard Braun <address@hidden>
Date:   Wed Nov 6 01:44:09 2013 +0100

    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.
---
 pfinet/glue-include/linux/interrupt.h | 2 ++
 pfinet/loopback.c                     | 7 +++++++
 pfinet/sched.c                        | 7 ++++++-
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/pfinet/glue-include/linux/interrupt.h 
b/pfinet/glue-include/linux/interrupt.h
index df58d2f..22312ba 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 068cf3c..e15e426 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 8992774..af03ab4 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);

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