Commit 0a4666b5 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge
Browse files

xen/dev-evtchn: clean up locking in evtchn 



Define a new per_user_data mutex to serialize bind/unbind operations
to prevent them from racing with each other.  Fix error returns
and don't do a bind while holding a spinlock.

Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
parent c5cfef0f

drivers/xen/evtchn.c

+25 −12
Original line number Diff line number Diff line
@@ -54,6 +54,8 @@ 
#include <asm/xen/hypervisor.h>



struct per_user_data {

	struct mutex bind_mutex; /* serialize bind/unbind operations */



	/* Notification ring, accessed via /dev/xen/evtchn. */

#define EVTCHN_RING_SIZE     (PAGE_SIZE / sizeof(evtchn_port_t))

#define EVTCHN_RING_MASK(_i) ((_i)&(EVTCHN_RING_SIZE-1))
@@ -69,7 +71,7 @@ struct per_user_data { 


/* Who's bound to each port? */

static struct per_user_data *port_user[NR_EVENT_CHANNELS];

static DEFINE_SPINLOCK(port_user_lock);

static DEFINE_SPINLOCK(port_user_lock); /* protects port_user[] and ring_prod */



irqreturn_t evtchn_interrupt(int irq, void *data)

{
@@ -210,22 +212,24 @@ static ssize_t evtchn_write(struct file *file, const char __user *buf, 


static int evtchn_bind_to_user(struct per_user_data *u, int port)

{

	int irq;

	int rc = 0;



	spin_lock_irq(&port_user_lock);



	/*

	 * Ports are never reused, so every caller should pass in a

	 * unique port.

	 *

	 * (Locking not necessary because we haven't registered the

	 * interrupt handler yet, and our caller has already

	 * serialized bind operations.)

	 */

	BUG_ON(port_user[port] != NULL);

	port_user[port] = u;



	irq = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,

	rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,

				       u->name, (void *)(unsigned long)port);

	if (rc < 0)

		goto fail;



	port_user[port] = u;

	if (rc >= 0)

		rc = 0;



fail:

	spin_unlock_irq(&port_user_lock);

	return rc;

}
@@ -234,6 +238,10 @@ static void evtchn_unbind_from_user(struct per_user_data *u, int port) 
	int irq = irq_from_evtchn(port);



	unbind_from_irqhandler(irq, (void *)(unsigned long)port);



	/* make sure we unbind the irq handler before clearing the port */

	barrier();



	port_user[port] = NULL;

}
@@ -244,6 +252,9 @@ static long evtchn_ioctl(struct file *file, 
	struct per_user_data *u = file->private_data;

	void __user *uarg = (void __user *) arg;



	/* Prevent bind from racing with unbind */

	mutex_lock(&u->bind_mutex);



	switch (cmd) {

	case IOCTL_EVTCHN_BIND_VIRQ: {

		struct ioctl_evtchn_bind_virq bind;
@@ -368,6 +379,7 @@ static long evtchn_ioctl(struct file *file, 
		rc = -ENOSYS;

		break;

	}

	mutex_unlock(&u->bind_mutex);



	return rc;

}
@@ -414,6 +426,7 @@ static int evtchn_open(struct inode *inode, struct file *filp) 
		return -ENOMEM;

	}



	mutex_init(&u->bind_mutex);

	mutex_init(&u->ring_cons_mutex);



	filp->private_data = u;