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SubjectRe: [PATCH 5/8] staging: vme: add functions for bridge module refcounting
On 01/08/11 11:20, Manohar Vanga wrote:
> This patch adds functions that allow for reference counting
> bridge modules. The patch introduces the functions
> 'vme_bridge_get()' and 'vme_bridge_put()'.
>
> This patch is based on the changes introduced by Emilio G. Cota
> in the patch:
>
> https://lkml.org/lkml/2010/10/25/492
>
> Signed-off-by: Manohar Vanga <manohar.vanga@cern.ch>
> ---
> drivers/staging/vme/bridges/vme_ca91cx42.c | 2 +
> drivers/staging/vme/bridges/vme_tsi148.c | 2 +
> drivers/staging/vme/devices/vme_user.c | 20 +++++++++++
> drivers/staging/vme/vme.c | 48 ++++++++++++++++++++++++++++
> drivers/staging/vme/vme.h | 2 +
> drivers/staging/vme/vme_bridge.h | 1 +
> 6 files changed, 75 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/staging/vme/bridges/vme_ca91cx42.c b/drivers/staging/vme/bridges/vme_ca91cx42.c
> index 15a0b19..2f9c22b 100644
> --- a/drivers/staging/vme/bridges/vme_ca91cx42.c
> +++ b/drivers/staging/vme/bridges/vme_ca91cx42.c
> @@ -1680,6 +1680,8 @@ static int ca91cx42_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> ca91cx42_bridge->parent = &pdev->dev;
> strcpy(ca91cx42_bridge->name, driver_name);
>
> + ca91cx42_bridge->owner = THIS_MODULE;
> +
> /* Setup IRQ */
> retval = ca91cx42_irq_init(ca91cx42_bridge);
> if (retval != 0) {
> diff --git a/drivers/staging/vme/bridges/vme_tsi148.c b/drivers/staging/vme/bridges/vme_tsi148.c
> index 5c147d6..9db89dc 100644
> --- a/drivers/staging/vme/bridges/vme_tsi148.c
> +++ b/drivers/staging/vme/bridges/vme_tsi148.c
> @@ -2320,6 +2320,8 @@ static int tsi148_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> tsi148_bridge->parent = &pdev->dev;
> strcpy(tsi148_bridge->name, driver_name);
>
> + tsi148_bridge->owner = THIS_MODULE;
> +
> /* Setup IRQ */
> retval = tsi148_irq_init(tsi148_bridge);
> if (retval != 0) {
> diff --git a/drivers/staging/vme/devices/vme_user.c b/drivers/staging/vme/devices/vme_user.c
> index 3cbeb2a..7ed4a5c 100644
> --- a/drivers/staging/vme/devices/vme_user.c
> +++ b/drivers/staging/vme/devices/vme_user.c
> @@ -118,6 +118,8 @@ static struct cdev *vme_user_cdev; /* Character device */
> static struct class *vme_user_sysfs_class; /* Sysfs class */
> static struct device *vme_user_bridge; /* Pointer to bridge device */
>
> +static struct vme_bridge *vme_user_bus; /* Pointer to bridge */
> +
>
> static const int type[VME_DEVS] = { MASTER_MINOR, MASTER_MINOR,
> MASTER_MINOR, MASTER_MINOR,
> @@ -824,10 +826,25 @@ static int __devinit vme_user_probe(struct device *dev, int cur_bus,
> }
> }
>
> + /*
> + * Increment reference count of bridge module. We don't want things
> + * to fall over in case the bridge module is removed while the vme_user
> + * driver is still loaded.
> + */
> + vme_user_bus = vme_bridge_get(cur_bus);
> + if (!vme_user_bus) {
> + printk(KERN_ERR "%s: vme_bridge_get failed\n", driver_name);
> + err = -EINVAL;
> + goto err_bridge_get;
> + }
> +

Can we not do this inside vme_master_request, vme_slave_request, etc?

I.e. Add reference count when resources are given out.

> return 0;
>
> /* Ensure counter set correcty to destroy all sysfs devices */
> i = VME_DEVS;
> +err_bridge_get:
> + for (i = 0; i < VME_DEVS; i++)
> + device_destroy(vme_user_sysfs_class, MKDEV(VME_MAJOR, i));
> err_sysfs:
> while (i > 0) {
> i--;
> @@ -892,6 +909,9 @@ static int __devexit vme_user_remove(struct device *dev, int cur_bus,
> /* Unregiser the major and minor device numbers */
> unregister_chrdev_region(MKDEV(VME_MAJOR, 0), VME_DEVS);
>
> + /* decrement bridge module reference */
> + vme_bridge_put(vme_user_bus);
> +

This would then be done in the vme_*_free routines.

Martyn

> return 0;
> }
>
> diff --git a/drivers/staging/vme/vme.c b/drivers/staging/vme/vme.c
> index 11e28ca..759ec2b 100644
> --- a/drivers/staging/vme/vme.c
> +++ b/drivers/staging/vme/vme.c
> @@ -52,6 +52,54 @@ static struct vme_bridge *dev_to_bridge(struct device *dev)
> }
>
> /*
> + * Increments the reference count of a VME bridge.
> + *
> + * If found, a pointer to the bridge is returned and the reference count
> + * of the module that owns it is incremented.
> + *
> + * On success, it can be assumed that the bridge won't be removed until
> + * the corresponding call to vme_put_bridge().
> + *
> + * Normally drivers should call vme_get_bridge() on a successfull .probe,
> + * and vme_put_bridge() when releasing the device, e.g. in .remove.
> + */
> +struct vme_bridge *vme_bridge_get(unsigned int bus_id)
> +{
> + struct vme_bridge *bridge;
> + struct vme_bridge *retp = NULL;
> +
> + mutex_lock(&vme_buses_lock);
> + list_for_each_entry(bridge, &vme_bus_list, bus_list) {
> + if (bridge->num == bus_id) {
> + if (!bridge->owner)
> + dev_warn(bridge->parent,
> + "bridge->owner not set\n");
> + else if (try_module_get(bridge->owner))
> + retp = bridge;
> + break;
> + }
> + }
> + mutex_unlock(&vme_buses_lock);
> + return retp;
> +}
> +EXPORT_SYMBOL(vme_bridge_get);
> +
> +/*
> + * Decrements the reference count of a bridge
> + *
> + * This function decrements the reference count of the module that controls
> + * the bridge. It must come after a call to vme_get_bridge().
> + */
> +void vme_bridge_put(struct vme_bridge *bridge)
> +{
> + if (!bridge->owner)
> + dev_warn(bridge->parent, "bridge->owner not set\n");
> + else
> + module_put(bridge->owner);
> +}
> +EXPORT_SYMBOL(vme_bridge_put);
> +
> +/*
> * Find the bridge that the resource is associated with.
> */
> static struct vme_bridge *find_bridge(struct vme_resource *resource)
> diff --git a/drivers/staging/vme/vme.h b/drivers/staging/vme/vme.h
> index 3ccb497..8fb35e2 100644
> --- a/drivers/staging/vme/vme.h
> +++ b/drivers/staging/vme/vme.h
> @@ -167,6 +167,8 @@ int vme_slot_get(struct device *);
> int vme_register_driver(struct vme_driver *);
> void vme_unregister_driver(struct vme_driver *);
>
> +struct vme_bridge *vme_bridge_get(unsigned int bus_id);
> +void vme_bridge_put(struct vme_bridge *bridge);
>
> #endif /* _VME_H_ */
>
> diff --git a/drivers/staging/vme/vme_bridge.h b/drivers/staging/vme/vme_bridge.h
> index 8959670..ef751a4 100644
> --- a/drivers/staging/vme/vme_bridge.h
> +++ b/drivers/staging/vme/vme_bridge.h
> @@ -113,6 +113,7 @@ struct vme_bridge {
> struct device *parent; /* Parent device (eg. pdev->dev for PCI) */
> void *driver_priv; /* Private pointer for the bridge driver */
> struct list_head bus_list; /* list of VME buses */
> + struct module *owner; /* module that owns the bridge */
>
> struct device dev[VME_SLOTS_MAX]; /* Device registered with
> * device model on VME bus


--
Martyn Welch (Principal Software Engineer) | Registered in England and
GE Intelligent Platforms | Wales (3828642) at 100
T +44(0)127322748 | Barbirolli Square, Manchester,
E martyn.welch@ge.com | M2 3AB VAT:GB 927559189

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