The patch titled
driver core: fix bus_rescan_devices() race.
has been added to the -mm tree. Its filename is
driver-core-fix-bus_rescan_devices-race.patch
Patches currently in -mm which might be from [EMAIL PROTECTED] are
driver-core-fix-bus_rescan_devices-race.patch
yenta-make-topic95-bridges-work-with-16bit-cards.patch
pcmcia-cs-fix-possible-missed-wakeup.patch
fix-pcmcia_request_irq-for-multifunction-card.patch
pcmcia-yenta-avoid-pci-write-posting-problem.patch
yenta-auto-tune-ene-bridges-for-cb-cards.patch
From: Daniel Ritz <[EMAIL PROTECTED]>
bus_rescan_devices_helper() does not hold the dev->sem when it checks for
!dev->driver. device_attach() holds the sem, but calls again
device_bind_driver() even when dev->driver is set (which means device is
already bound to a driver). what happens is that a first device_attach()
call (module insertion time) is on the way binding the device to a driver.
another thread calls bus_rescan_devices().
Now when bus_rescan_devices_helper() checks for dev->driver it is still
NULL 'cos the the prior device_attach() is not yet finished. but as soon
as the first one releases the dev->sem the second device_attach() tries to
rebind the already bound device again. device_bind_driver() does this
blindly which leads to a corrupt driver->klist_devices list (the device
links itself, the head points to the device).
Later a call to device_release_driver() sets dev->driver to NULL and breaks
the link it has to itself on knode_driver. rmmoding the driver later calls
driver_detach() which leads to an endless loop 'cos the list head in
klist_devices still points to the device. and since dev->driver is NULL
it's stuck with the same device forever. boom. and rmmod hangs.
Very easy to reproduce with new-style pcmcia and a 16bit card. just loop
modprobe <pcmcia-modules> ;cardctl eject; rmmod <card driver, pcmcia
modules>.
Fix is not to call device_bind_driver() in device_attach() if dev->driver
is non-NULL. this is wrong anyway since if dev->driver is set the device
is bound. also remove the dev->drv check in bus_rescan_devices_helper().
And while at it replace spin_(un|)lock_irq in driver_detach with the
non-irq variants. just doesn't make sense to me. The whole klist locking
never uses the irq variants.
Signed-off-by: Daniel Ritz <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---
drivers/base/bus.c | 3 +--
drivers/base/dd.c | 11 +++++------
2 files changed, 6 insertions(+), 8 deletions(-)
diff -puN drivers/base/bus.c~driver-core-fix-bus_rescan_devices-race
drivers/base/bus.c
--- devel/drivers/base/bus.c~driver-core-fix-bus_rescan_devices-race
2005-08-22 17:44:11.000000000 -0700
+++ devel-akpm/drivers/base/bus.c 2005-08-22 17:44:11.000000000 -0700
@@ -485,8 +485,7 @@ void bus_remove_driver(struct device_dri
/* Helper for bus_rescan_devices's iter */
static int bus_rescan_devices_helper(struct device *dev, void *data)
{
- if (!dev->driver)
- device_attach(dev);
+ device_attach(dev);
return 0;
}
diff -puN drivers/base/dd.c~driver-core-fix-bus_rescan_devices-race
drivers/base/dd.c
--- devel/drivers/base/dd.c~driver-core-fix-bus_rescan_devices-race
2005-08-22 17:44:11.000000000 -0700
+++ devel-akpm/drivers/base/dd.c 2005-08-22 17:44:11.000000000 -0700
@@ -127,10 +127,9 @@ int device_attach(struct device * dev)
int ret = 0;
down(&dev->sem);
- if (dev->driver) {
- device_bind_driver(dev);
+ if (dev->driver)
ret = 1;
- } else
+ else
ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
up(&dev->sem);
return ret;
@@ -222,15 +221,15 @@ void driver_detach(struct device_driver
struct device * dev;
for (;;) {
- spin_lock_irq(&drv->klist_devices.k_lock);
+ spin_lock(&drv->klist_devices.k_lock);
if (list_empty(&drv->klist_devices.k_list)) {
- spin_unlock_irq(&drv->klist_devices.k_lock);
+ spin_unlock(&drv->klist_devices.k_lock);
break;
}
dev = list_entry(drv->klist_devices.k_list.prev,
struct device, knode_driver.n_node);
get_device(dev);
- spin_unlock_irq(&drv->klist_devices.k_lock);
+ spin_unlock(&drv->klist_devices.k_lock);
down(&dev->sem);
if (dev->driver == drv)
_
-
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