Hi Jeremy,
this patch switches back from spinlocks to rwlocks in gntdev, solving
the locking issue that was preventing stubdoms from working.
In particular the problem is that gntdev_mmap calls apply_to_page_range
after acquiring the spinlock. apply_to_page_range causes the mmu
notifiers to be called, so mn_invl_range_start will be called that will
try to acquire again the same spinlock.
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index a33e443..0a9a68c 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -51,7 +51,7 @@ struct gntdev_priv {
struct list_head maps;
uint32_t used;
uint32_t limit;
- spinlock_t lock;
+ rwlock_t rwlock;
struct mm_struct *mm;
struct mmu_notifier mn;
};
@@ -289,7 +289,7 @@ static void mn_invl_range_start(struct mmu_notifier *mn,
unsigned long mstart, mend;
int err;
- spin_lock(&priv->lock);
+ read_lock(&priv->rwlock);
list_for_each_entry(map, &priv->maps, next) {
if (!map->vma)
continue;
@@ -311,7 +311,7 @@ static void mn_invl_range_start(struct mmu_notifier *mn,
(mend - mstart) >> PAGE_SHIFT);
WARN_ON(err);
}
- spin_unlock(&priv->lock);
+ read_unlock(&priv->rwlock);
}
static void mn_invl_page(struct mmu_notifier *mn,
@@ -328,7 +328,7 @@ static void mn_release(struct mmu_notifier *mn,
struct grant_map *map;
int err;
- spin_lock(&priv->lock);
+ read_lock(&priv->rwlock);
list_for_each_entry(map, &priv->maps, next) {
if (!map->vma)
continue;
@@ -339,7 +339,7 @@ static void mn_release(struct mmu_notifier *mn,
err = unmap_grant_pages(map, 0, map->count);
WARN_ON(err);
}
- spin_unlock(&priv->lock);
+ read_unlock(&priv->rwlock);
}
struct mmu_notifier_ops gntdev_mmu_ops = {
@@ -359,7 +359,7 @@ static int gntdev_open(struct inode *inode, struct file
*flip)
return -ENOMEM;
INIT_LIST_HEAD(&priv->maps);
- spin_lock_init(&priv->lock);
+ priv->rwlock = RW_LOCK_UNLOCKED;
priv->limit = limit;
priv->mm = get_task_mm(current);
@@ -387,7 +387,7 @@ static int gntdev_release(struct inode *inode, struct file
*flip)
if (debug)
printk("%s: priv %p\n", __FUNCTION__, priv);
- spin_lock(&priv->lock);
+ write_lock(&priv->rwlock);
while (!list_empty(&priv->maps)) {
map = list_entry(priv->maps.next, struct grant_map, next);
err = gntdev_del_map(map);
@@ -395,7 +395,7 @@ static int gntdev_release(struct inode *inode, struct file
*flip)
gntdev_free_map(map);
}
- spin_unlock(&priv->lock);
+ write_unlock(&priv->rwlock);
mmu_notifier_unregister(&priv->mn, priv->mm);
kfree(priv);
@@ -429,15 +429,15 @@ static long gntdev_ioctl_map_grant_ref(struct gntdev_priv
*priv,
return err;
}
- spin_lock(&priv->lock);
+ write_lock(&priv->rwlock);
gntdev_add_map(priv, map);
op.index = map->index << PAGE_SHIFT;
- spin_unlock(&priv->lock);
+ write_unlock(&priv->rwlock);
if (copy_to_user(u, &op, sizeof(op)) != 0) {
- spin_lock(&priv->lock);
+ write_lock(&priv->rwlock);
gntdev_del_map(map);
- spin_unlock(&priv->lock);
+ write_unlock(&priv->rwlock);
gntdev_free_map(map);
return err;
}
@@ -457,11 +457,11 @@ static long gntdev_ioctl_unmap_grant_ref(struct
gntdev_priv *priv,
printk("%s: priv %p, del %d+%d\n", __FUNCTION__, priv,
(int)op.index, (int)op.count);
- spin_lock(&priv->lock);
+ write_lock(&priv->rwlock);
map = gntdev_find_map_index(priv, op.index >> PAGE_SHIFT, op.count);
if (map)
err = gntdev_del_map(map);
- spin_unlock(&priv->lock);
+ write_unlock(&priv->rwlock);
if (!err)
gntdev_free_map(map);
return err;
@@ -479,16 +479,16 @@ static long gntdev_ioctl_get_offset_for_vaddr(struct
gntdev_priv *priv,
printk("%s: priv %p, offset for vaddr %lx\n", __FUNCTION__,
priv,
(unsigned long)op.vaddr);
- spin_lock(&priv->lock);
+ read_lock(&priv->rwlock);
map = gntdev_find_map_vaddr(priv, op.vaddr);
if (map == NULL ||
map->vma->vm_start != op.vaddr) {
- spin_unlock(&priv->lock);
+ read_unlock(&priv->rwlock);
return -EINVAL;
}
op.offset = map->index << PAGE_SHIFT;
op.count = map->count;
- spin_unlock(&priv->lock);
+ read_unlock(&priv->rwlock);
if (copy_to_user(u, &op, sizeof(op)) != 0)
return -EFAULT;
@@ -507,9 +507,9 @@ static long gntdev_ioctl_set_max_grants(struct gntdev_priv
*priv,
if (op.count > limit)
return -EINVAL;
- spin_lock(&priv->lock);
+ write_lock(&priv->rwlock);
priv->limit = op.count;
- spin_unlock(&priv->lock);
+ write_unlock(&priv->rwlock);
return 0;
}
@@ -557,7 +557,7 @@ static int gntdev_mmap(struct file *flip, struct
vm_area_struct *vma)
printk("%s: map %d+%d at %lx (pgoff %lx)\n", __FUNCTION__,
index, count, vma->vm_start, vma->vm_pgoff);
- spin_lock(&priv->lock);
+ read_lock(&priv->rwlock);
map = gntdev_find_map_index(priv, index, count);
if (!map)
goto unlock_out;
@@ -599,7 +599,7 @@ static int gntdev_mmap(struct file *flip, struct
vm_area_struct *vma)
map->is_mapped = 1;
unlock_out:
- spin_unlock(&priv->lock);
+ read_unlock(&priv->rwlock);
return err;
}
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