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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: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
This commit is contained in:
Jeremy Fitzhardinge 2009-02-12 13:03:24 -08:00
parent c5cfef0f79
commit 0a4666b539
1 changed files with 25 additions and 12 deletions
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37
drivers/xen/evtchn.c
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@ -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);
irq = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,
u->name, (void *)(unsigned long)port);
if (rc < 0)
goto fail;
port_user[port] = u;
fail:
spin_unlock_irq(&port_user_lock);
rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,
u->name, (void *)(unsigned long)port);
if (rc >= 0)
rc = 0;
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;