From: Martin Schwidefsky <[email protected]>
[S390] dasd deadlock after state change pending interrupt.
The dasd_device_from_cdev function is called from interrupt context
to get the struct dasd_device associated with a ccw device. The
driver_data of the ccw device points to the dasd_devmap structure
which contains the pointer to the dasd_device structure. The lock
that protects the dasd_devmap structure is acquire with out irqsave.
To prevent the deadlock in dasd_device_from_cdev if it is called
from interrupt context the dependency to the dasd_devmap structure
needs to be removed. Let the driver_data of the ccw device point
to the dasd_device structure directly and use the ccw device lock
to protect the access.
Signed-off-by: Martin Schwidefsky <[email protected]>
---
drivers/s390/block/dasd.c | 4 +-
drivers/s390/block/dasd_devmap.c | 74 +++++++++++++++++++++++++--------------
drivers/s390/block/dasd_int.h | 1
3 files changed, 51 insertions(+), 28 deletions(-)
diff -urpN linux-2.6/drivers/s390/block/dasd.c linux-2.6-patched/drivers/s390/block/dasd.c
--- linux-2.6/drivers/s390/block/dasd.c 2006-08-24 12:10:54.000000000 +0200
+++ linux-2.6-patched/drivers/s390/block/dasd.c 2006-08-24 12:10:59.000000000 +0200
@@ -893,7 +893,7 @@ dasd_handle_killed_request(struct ccw_de
device = (struct dasd_device *) cqr->device;
if (device == NULL ||
- device != dasd_device_from_cdev(cdev) ||
+ device != dasd_device_from_cdev_locked(cdev) ||
strncmp(device->discipline->ebcname, (char *) &cqr->magic, 4)) {
MESSAGE(KERN_DEBUG, "invalid device in request: bus_id %s",
cdev->dev.bus_id);
@@ -970,7 +970,7 @@ dasd_int_handler(struct ccw_device *cdev
/* first of all check for state change pending interrupt */
mask = DEV_STAT_ATTENTION | DEV_STAT_DEV_END | DEV_STAT_UNIT_EXCEP;
if ((irb->scsw.dstat & mask) == mask) {
- device = dasd_device_from_cdev(cdev);
+ device = dasd_device_from_cdev_locked(cdev);
if (!IS_ERR(device)) {
dasd_handle_state_change_pending(device);
dasd_put_device(device);
diff -urpN linux-2.6/drivers/s390/block/dasd_devmap.c linux-2.6-patched/drivers/s390/block/dasd_devmap.c
--- linux-2.6/drivers/s390/block/dasd_devmap.c 2006-08-24 12:10:21.000000000 +0200
+++ linux-2.6-patched/drivers/s390/block/dasd_devmap.c 2006-08-24 12:10:59.000000000 +0200
@@ -523,17 +523,17 @@ dasd_create_device(struct ccw_device *cd
{
struct dasd_devmap *devmap;
struct dasd_device *device;
+ unsigned long flags;
int rc;
devmap = dasd_devmap_from_cdev(cdev);
if (IS_ERR(devmap))
return (void *) devmap;
- cdev->dev.driver_data = devmap;
device = dasd_alloc_device();
if (IS_ERR(device))
return device;
- atomic_set(&device->ref_count, 2);
+ atomic_set(&device->ref_count, 3);
spin_lock(&dasd_devmap_lock);
if (!devmap->device) {
@@ -552,6 +552,11 @@ dasd_create_device(struct ccw_device *cd
dasd_free_device(device);
return ERR_PTR(rc);
}
+
+ spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
+ cdev->dev.driver_data = device;
+ spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
+
return device;
}
@@ -569,6 +574,7 @@ dasd_delete_device(struct dasd_device *d
{
struct ccw_device *cdev;
struct dasd_devmap *devmap;
+ unsigned long flags;
/* First remove device pointer from devmap. */
devmap = dasd_find_busid(device->cdev->dev.bus_id);
@@ -582,9 +588,16 @@ dasd_delete_device(struct dasd_device *d
devmap->device = NULL;
spin_unlock(&dasd_devmap_lock);
- /* Drop ref_count by 2, one for the devmap reference and
- * one for the passed reference. */
- atomic_sub(2, &device->ref_count);
+ /* Disconnect dasd_device structure from ccw_device structure. */
+ spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
+ device->cdev->dev.driver_data = NULL;
+ spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
+
+ /*
+ * Drop ref_count by 3, one for the devmap reference, one for
+ * the cdev reference and one for the passed reference.
+ */
+ atomic_sub(3, &device->ref_count);
/* Wait for reference counter to drop to zero. */
wait_event(dasd_delete_wq, atomic_read(&device->ref_count) == 0);
@@ -593,9 +606,6 @@ dasd_delete_device(struct dasd_device *d
cdev = device->cdev;
device->cdev = NULL;
- /* Disconnect dasd_devmap structure from ccw_device structure. */
- cdev->dev.driver_data = NULL;
-
/* Put ccw_device structure. */
put_device(&cdev->dev);
@@ -615,21 +625,32 @@ dasd_put_device_wake(struct dasd_device
/*
* Return dasd_device structure associated with cdev.
+ * This function needs to be called with the ccw device
+ * lock held. It can be used from interrupt context.
+ */
+struct dasd_device *
+dasd_device_from_cdev_locked(struct ccw_device *cdev)
+{
+ struct dasd_device *device = cdev->dev.driver_data;
+
+ if (!device)
+ return ERR_PTR(-ENODEV);
+ dasd_get_device(device);
+ return device;
+}
+
+/*
+ * Return dasd_device structure associated with cdev.
*/
struct dasd_device *
dasd_device_from_cdev(struct ccw_device *cdev)
{
- struct dasd_devmap *devmap;
struct dasd_device *device;
+ unsigned long flags;
- device = ERR_PTR(-ENODEV);
- spin_lock(&dasd_devmap_lock);
- devmap = cdev->dev.driver_data;
- if (devmap && devmap->device) {
- device = devmap->device;
- dasd_get_device(device);
- }
- spin_unlock(&dasd_devmap_lock);
+ spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
+ device = dasd_device_from_cdev_locked(cdev);
+ spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
return device;
}
@@ -730,16 +751,17 @@ static ssize_t
dasd_discipline_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
- struct dasd_devmap *devmap;
- char *dname;
+ struct dasd_device *device;
+ ssize_t len;
- spin_lock(&dasd_devmap_lock);
- dname = "none";
- devmap = dev->driver_data;
- if (devmap && devmap->device && devmap->device->discipline)
- dname = devmap->device->discipline->name;
- spin_unlock(&dasd_devmap_lock);
- return snprintf(buf, PAGE_SIZE, "%s\n", dname);
+ device = dasd_device_from_cdev(to_ccwdev(dev));
+ if (!IS_ERR(device) && device->discipline) {
+ len = snprintf(buf, PAGE_SIZE, "%s\n",
+ device->discipline->name);
+ dasd_put_device(device);
+ } else
+ len = snprintf(buf, PAGE_SIZE, "none\n");
+ return len;
}
static DEVICE_ATTR(discipline, 0444, dasd_discipline_show, NULL);
diff -urpN linux-2.6/drivers/s390/block/dasd_int.h linux-2.6-patched/drivers/s390/block/dasd_int.h
--- linux-2.6/drivers/s390/block/dasd_int.h 2006-08-24 12:09:53.000000000 +0200
+++ linux-2.6-patched/drivers/s390/block/dasd_int.h 2006-08-24 12:10:59.000000000 +0200
@@ -534,6 +534,7 @@ int dasd_add_sysfs_files(struct ccw_devi
void dasd_remove_sysfs_files(struct ccw_device *);
struct dasd_device *dasd_device_from_cdev(struct ccw_device *);
+struct dasd_device *dasd_device_from_cdev_locked(struct ccw_device *);
struct dasd_device *dasd_device_from_devindex(int);
int dasd_parse(void);