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Commit b597ef47 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by David S. Miller
Browse files

[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: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4fef0304

drivers/net/shaper.c

+19 −67
Original line number Diff line number Diff line
@@ -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))

	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);

}



/*
@@ -310,19 +287,6 @@ 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);

}



/*

include/linux/if_shaper.h

+1 −2
Original line number Diff line number Diff line
@@ -23,7 +23,7 @@ struct shaper 
	__u32 shapeclock;

	unsigned long recovery;	/* Time we can next clock a packet out on

				   an empty queue */

        unsigned long locked;

	struct semaphore sem;

        struct net_device_stats stats;

	struct net_device *dev;

	int  (*hard_start_xmit) (struct sk_buff *skb,
@@ -38,7 +38,6 @@ struct shaper 
	int (*hard_header_cache)(struct neighbour *neigh, struct hh_cache *hh);

	void (*header_cache_update)(struct hh_cache *hh, struct net_device *dev, unsigned char *  haddr);

	struct net_device_stats* (*get_stats)(struct net_device *dev);

	wait_queue_head_t  wait_queue;

	struct timer_list timer;

};