[S390] dasd: fix race condition in resume code

There is a race while re-reading the device characteristics. After
cleaning the memory area a cqr is build which reads the device
characteristics. This may take a rather long time and the device
characteristics structure is zero during this. Now it could be
possible that the block tasklet starts working and a new cqr will be
build. The build_cp command refers to the device characteristics
structure and this may lead into a divide by zero exception.
Fix this by re-reading the device characteristics into a temporary
structur and copy the data to the original structure. Also take the
ccwdev_lock.

Signed-off-by: Stefan Haberland <stefan.haberland@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index dad0449475b6..53b8c255360a 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -2508,8 +2508,6 @@ int dasd_generic_restore_device(struct ccw_device *cdev)
         device->stopped &= ~DASD_UNRESUMED_PM;
 
         dasd_schedule_device_bh(device);
-        if (device->block)
-                dasd_schedule_block_bh(device->block);
 
         if (device->discipline->restore)
                 rc = device->discipline->restore(device);
@@ -2520,6 +2518,9 @@ int dasd_generic_restore_device(struct ccw_device *cdev)
                  */
                 device->stopped |= DASD_UNRESUMED_PM;
 
+        if (device->block)
+                dasd_schedule_block_bh(device->block);
+
         dasd_put_device(device);
         return 0;
 }