[NET]: Fix locking in shaper driver.

 o use a semaphore instead of an opencoded and racy lock
 o move locking out of shaper_kick and into the callers - most just
   released the lock before calling shaper_kick
 o remove in_interrupt() tests.  from ->close we can always block, from
   ->hard_start_xmit and timer context never

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 19 insertions, 67 deletions

diff --git a/drivers/net/shaper.c b/drivers/net/shaper.c
index e68cf5fb4920..20edeb345792 100644
--- a/drivers/net/shaper.c
+++ b/drivers/net/shaper.c
@@ -100,35 +100,8 @@ static int sh_debug;		/* Debug flag */
 
 #define SHAPER_BANNER   "CymruNet Traffic Shaper BETA 0.04 for Linux 2.1\n"
 
-/*
- *      Locking
- */
- 
-static int shaper_lock(struct shaper *sh)
-{
-        /*
-         *      Lock in an interrupt must fail
-         */
-        while (test_and_set_bit(0, &sh->locked))
-        {
-                if (!in_interrupt())
-                        sleep_on(&sh->wait_queue);
-                else
-                        return 0;
-                        
-        }
-        return 1;
-}
-
 static void shaper_kick(struct shaper *sh);
 
-static void shaper_unlock(struct shaper *sh)
-{
-        clear_bit(0, &sh->locked);
-        wake_up(&sh->wait_queue);
-        shaper_kick(sh);
-}
-
 /*
  *      Compute clocks on a buffer
  */
@@ -157,17 +130,15 @@ static void shaper_setspeed(struct shaper *shaper, int bitspersec)
  *      Throw a frame at a shaper.
  */
   
-static int shaper_qframe(struct shaper *shaper, struct sk_buff *skb)
+
+static int shaper_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
+        struct shaper *shaper = dev->priv;
         struct sk_buff *ptr;
    
-        /*
-         *      Get ready to work on this shaper. Lock may fail if its
-         *      an interrupt and locked.
-         */
-         
-        if(!shaper_lock(shaper))
-                return -1;
+        if (down_trylock(&shaper->sem))
+                return -1;
+
         ptr=shaper->sendq.prev;
         
         /*
@@ -260,7 +231,8 @@ static int shaper_qframe(struct shaper *shaper, struct sk_buff *skb)
                 dev_kfree_skb(ptr);
                 shaper->stats.collisions++;
         }
-        shaper_unlock(shaper);
+        shaper_kick(shaper);
+        up(&shaper->sem);
         return 0;
 }
 
@@ -297,8 +269,13 @@ static void shaper_queue_xmit(struct shaper *shaper, struct sk_buff *skb)
  
 static void shaper_timer(unsigned long data)
 {
-        struct shaper *sh=(struct shaper *)data;
-        shaper_kick(sh);
+        struct shaper *shaper = (struct shaper *)data;
+
+        if (!down_trylock(&shaper->sem)) {
+                shaper_kick(shaper);
+                up(&shaper->sem);
+        } else
+                mod_timer(&shaper->timer, jiffies);
 }
 
 /*
@@ -311,19 +288,6 @@ static void shaper_kick(struct shaper *shaper)
         struct sk_buff *skb;
         
         /*
-         *      Shaper unlock will kick
-         */
-         
-        if (test_and_set_bit(0, &shaper->locked))
-        {
-                if(sh_debug)
-                        printk("Shaper locked.\n");
-                mod_timer(&shaper->timer, jiffies);
-                return;
-        }
-
-                
-        /*
          *      Walk the list (may be empty)
          */
          
@@ -364,8 +328,6 @@ static void shaper_kick(struct shaper *shaper)
          
         if(skb!=NULL)
                 mod_timer(&shaper->timer, SHAPERCB(skb)->shapeclock);
-
-        clear_bit(0, &shaper->locked);
 }
 
 
@@ -376,14 +338,12 @@ static void shaper_kick(struct shaper *shaper)
 static void shaper_flush(struct shaper *shaper)
 {
         struct sk_buff *skb;
-        if(!shaper_lock(shaper))
-        {
-                printk(KERN_ERR "shaper: shaper_flush() called by an irq!\n");
-                return;
-        }
+
+        down(&shaper->sem);
         while((skb=skb_dequeue(&shaper->sendq))!=NULL)
                 dev_kfree_skb(skb);
-        shaper_unlock(shaper);
+        shaper_kick(shaper);
+        up(&shaper->sem);
 }
 
 /*
@@ -426,13 +386,6 @@ static int shaper_close(struct net_device *dev)
  *      ARP and other resolutions and not before.
  */
 
-
-static int shaper_start_xmit(struct sk_buff *skb, struct net_device *dev)
-{
-        struct shaper *sh=dev->priv;
-        return shaper_qframe(sh, skb);
-}
-
 static struct net_device_stats *shaper_get_stats(struct net_device *dev)
 {
         struct shaper *sh=dev->priv;
@@ -623,7 +576,6 @@ static void shaper_init_priv(struct net_device *dev)
         init_timer(&sh->timer);
         sh->timer.function=shaper_timer;
         sh->timer.data=(unsigned long)sh;
-        init_waitqueue_head(&sh->wait_queue);
 }
 
 /*