Re: PCI driver module unload race?

Greg KH
2003-03-08T19:12:11Z

On Sat, Mar 08, 2003 at 10:47:49AM +0000, Russell King wrote:
> Hi,
>
> What prevents the following scenario from happening? It's purely
> theoretical - I haven't seen this occuring.
>
> - Load PCI driver.
>
> - PCI driver registers using pci_module_init(), and adds itself to sysfs.
>
> - Hot-plugin a PCI device which uses this driver. sysfs matches the PCI
> driver, and calls the PCI drivers probe function.

Ugh, yes you are correct, I can't believe I missed this before.

How does this patch look?

thanks,

greg k-h

===== drivers/pci/pci-driver.c 1.17 vs edited =====
--- 1.17/drivers/pci/pci-driver.c Sat Nov 23 13:23:03 2002
+++ edited/drivers/pci/pci-driver.c Sat Mar 8 11:21:06 2003
@@ -48,6 +48,12 @@
if (!pci_dev->driver && drv->probe) {
const struct pci_device_id *id;

+ if (!try_module_get(drv->owner)) {
+ dev_err(dev, "Can't get a module reference for %s\n",
+ drv->name);
+ error = -ENODEV;
+ goto exit;
+ }
id = pci_match_device(drv->id_table, pci_dev);
if (id)
error = drv->probe(pci_dev, id);
@@ -55,7 +61,9 @@
pci_dev->driver = drv;
error = 0;
}
+ module_put(drv->owner);
}
+exit:
return error;
}

@@ -66,7 +74,10 @@

if (drv) {
if (drv->remove)
- drv->remove(pci_dev);
+ if (try_module_get(drv->owner)) {
+ drv->remove(pci_dev);
+ module_put(drv->owner);
+ }
pci_dev->driver = NULL;
}
return 0;
===== include/linux/pci.h 1.36 vs edited =====
--- 1.36/include/linux/pci.h Tue Mar 4 21:09:58 2003
+++ edited/include/linux/pci.h Sat Mar 8 11:20:15 2003
@@ -493,6 +493,7 @@

struct pci_driver {
struct list_head node;
+ struct module *owner;
char *name;
const struct pci_device_id *id_table; /* NULL if wants all devices */
int (*probe) (struct pci_dev *dev, const struct pci_device_id *id); /* New device inserted */