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hvc/xen: lock console list traversal
The currently lockless access to the xen console list in
vtermno_to_xencons() is incorrect, as additions and removals from the
list can happen anytime, and as such the traversal of the list to get
the private console data for a given termno needs to happen with the
lock held. Note users that modify the list already do so with the
lock taken.
Adjust current lock takers to use the _irq{save,restore} helpers,
since the context in which vtermno_to_xencons() is called can have
interrupts disabled. Use the _irq{save,restore} set of helpers to
switch the current callers to disable interrupts in the locked region.
I haven't checked if existing users could instead use the _irq
variant, as I think it's safer to use _irq{save,restore} upfront.
While there switch from using list_for_each_entry_safe to
list_for_each_entry: the current entry cursor won't be removed as
part of the code in the loop body, so using the _safe variant is
pointless.
Fixes: 02e19f9c7c
('hvc_xen: implement multiconsole support')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/20221130163611.14686-1-roger.pau@citrix.com
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
parent
37c1785609
commit
c0dccad87c
1 changed files with 29 additions and 17 deletions
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@ -52,17 +52,22 @@ static DEFINE_SPINLOCK(xencons_lock);
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static struct xencons_info *vtermno_to_xencons(int vtermno)
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static struct xencons_info *vtermno_to_xencons(int vtermno)
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{
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{
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struct xencons_info *entry, *n, *ret = NULL;
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struct xencons_info *entry, *ret = NULL;
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unsigned long flags;
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if (list_empty(&xenconsoles))
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spin_lock_irqsave(&xencons_lock, flags);
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if (list_empty(&xenconsoles)) {
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spin_unlock_irqrestore(&xencons_lock, flags);
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return NULL;
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return NULL;
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}
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list_for_each_entry_safe(entry, n, &xenconsoles, list) {
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list_for_each_entry(entry, &xenconsoles, list) {
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if (entry->vtermno == vtermno) {
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if (entry->vtermno == vtermno) {
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ret = entry;
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ret = entry;
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break;
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break;
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}
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}
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}
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}
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spin_unlock_irqrestore(&xencons_lock, flags);
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return ret;
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return ret;
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}
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}
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@ -223,7 +228,7 @@ static int xen_hvm_console_init(void)
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{
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{
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int r;
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int r;
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uint64_t v = 0;
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uint64_t v = 0;
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unsigned long gfn;
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unsigned long gfn, flags;
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struct xencons_info *info;
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struct xencons_info *info;
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if (!xen_hvm_domain())
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if (!xen_hvm_domain())
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@ -258,9 +263,9 @@ static int xen_hvm_console_init(void)
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goto err;
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goto err;
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info->vtermno = HVC_COOKIE;
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info->vtermno = HVC_COOKIE;
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spin_lock(&xencons_lock);
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spin_lock_irqsave(&xencons_lock, flags);
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list_add_tail(&info->list, &xenconsoles);
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list_add_tail(&info->list, &xenconsoles);
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spin_unlock(&xencons_lock);
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spin_unlock_irqrestore(&xencons_lock, flags);
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return 0;
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return 0;
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err:
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err:
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@ -283,6 +288,7 @@ static int xencons_info_pv_init(struct xencons_info *info, int vtermno)
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static int xen_pv_console_init(void)
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static int xen_pv_console_init(void)
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{
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{
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struct xencons_info *info;
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struct xencons_info *info;
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unsigned long flags;
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if (!xen_pv_domain())
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if (!xen_pv_domain())
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return -ENODEV;
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return -ENODEV;
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@ -299,9 +305,9 @@ static int xen_pv_console_init(void)
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/* already configured */
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/* already configured */
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return 0;
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return 0;
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}
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}
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spin_lock(&xencons_lock);
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spin_lock_irqsave(&xencons_lock, flags);
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xencons_info_pv_init(info, HVC_COOKIE);
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xencons_info_pv_init(info, HVC_COOKIE);
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spin_unlock(&xencons_lock);
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spin_unlock_irqrestore(&xencons_lock, flags);
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return 0;
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return 0;
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}
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}
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@ -309,6 +315,7 @@ static int xen_pv_console_init(void)
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static int xen_initial_domain_console_init(void)
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static int xen_initial_domain_console_init(void)
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{
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{
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struct xencons_info *info;
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struct xencons_info *info;
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unsigned long flags;
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if (!xen_initial_domain())
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if (!xen_initial_domain())
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return -ENODEV;
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return -ENODEV;
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@ -323,9 +330,9 @@ static int xen_initial_domain_console_init(void)
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info->irq = bind_virq_to_irq(VIRQ_CONSOLE, 0, false);
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info->irq = bind_virq_to_irq(VIRQ_CONSOLE, 0, false);
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info->vtermno = HVC_COOKIE;
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info->vtermno = HVC_COOKIE;
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spin_lock(&xencons_lock);
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spin_lock_irqsave(&xencons_lock, flags);
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list_add_tail(&info->list, &xenconsoles);
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list_add_tail(&info->list, &xenconsoles);
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spin_unlock(&xencons_lock);
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spin_unlock_irqrestore(&xencons_lock, flags);
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return 0;
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return 0;
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}
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}
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@ -380,10 +387,12 @@ static void xencons_free(struct xencons_info *info)
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static int xen_console_remove(struct xencons_info *info)
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static int xen_console_remove(struct xencons_info *info)
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{
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{
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unsigned long flags;
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xencons_disconnect_backend(info);
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xencons_disconnect_backend(info);
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spin_lock(&xencons_lock);
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spin_lock_irqsave(&xencons_lock, flags);
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list_del(&info->list);
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list_del(&info->list);
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spin_unlock(&xencons_lock);
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spin_unlock_irqrestore(&xencons_lock, flags);
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if (info->xbdev != NULL)
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if (info->xbdev != NULL)
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xencons_free(info);
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xencons_free(info);
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else {
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else {
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@ -464,6 +473,7 @@ static int xencons_probe(struct xenbus_device *dev,
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{
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{
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int ret, devid;
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int ret, devid;
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struct xencons_info *info;
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struct xencons_info *info;
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unsigned long flags;
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devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
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devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
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if (devid == 0)
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if (devid == 0)
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@ -482,9 +492,9 @@ static int xencons_probe(struct xenbus_device *dev,
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ret = xencons_connect_backend(dev, info);
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ret = xencons_connect_backend(dev, info);
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if (ret < 0)
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if (ret < 0)
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goto error;
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goto error;
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spin_lock(&xencons_lock);
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spin_lock_irqsave(&xencons_lock, flags);
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list_add_tail(&info->list, &xenconsoles);
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list_add_tail(&info->list, &xenconsoles);
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spin_unlock(&xencons_lock);
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spin_unlock_irqrestore(&xencons_lock, flags);
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return 0;
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return 0;
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@ -584,10 +594,12 @@ static int __init xen_hvc_init(void)
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info->hvc = hvc_alloc(HVC_COOKIE, info->irq, ops, 256);
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info->hvc = hvc_alloc(HVC_COOKIE, info->irq, ops, 256);
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if (IS_ERR(info->hvc)) {
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if (IS_ERR(info->hvc)) {
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unsigned long flags;
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r = PTR_ERR(info->hvc);
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r = PTR_ERR(info->hvc);
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spin_lock(&xencons_lock);
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spin_lock_irqsave(&xencons_lock, flags);
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list_del(&info->list);
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list_del(&info->list);
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spin_unlock(&xencons_lock);
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spin_unlock_irqrestore(&xencons_lock, flags);
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if (info->irq)
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if (info->irq)
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unbind_from_irqhandler(info->irq, NULL);
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unbind_from_irqhandler(info->irq, NULL);
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kfree(info);
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kfree(info);
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