[patch 46/52] [PATCH] cio: fix quiesce state

Martin Schwidefsky
2009-11-13T15:14:56Z

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From: Sebastian Ott <sebott@linux.vnet.ibm.com>

DEV_STATE_QUIESCE is used to stop all IO on a busy subchannel.
This patch fixes the following problems related to the QUIESCE
state:

* Fix a potential race condition which could occur when the
resulting state was DEV_STATE_OFFLINE.

* Add missing locking around cio_disable_subchannel,
ccw_device_cancel_halt_clear and the cdev's handler.

* Loop until we know for sure that the subchannel is disabled.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---

drivers/s390/cio/device.c | 35 +++++++++++++++++++----------------
drivers/s390/cio/device_fsm.c | 17 ++++-------------
2 files changed, 23 insertions(+), 29 deletions(-)

Index: quilt-2.6/drivers/s390/cio/device.c
===================================================================
--- quilt-2.6.orig/drivers/s390/cio/device.c 2009-11-13 16:08:22.000000000 +0100
+++ quilt-2.6/drivers/s390/cio/device.c 2009-11-13 16:08:22.000000000 +0100
@@ -1130,33 +1130,36 @@
return 0;
}

-static void
-io_subchannel_shutdown(struct subchannel *sch)
+static void io_subchannel_shutdown(struct subchannel *sch)
{
struct ccw_device *cdev;
int ret;

+ spin_lock_irq(sch->lock);
cdev = sch_get_cdev(sch);
-
if (cio_is_console(sch->schid))
- return;
+ goto out_unlock;
if (!sch->schib.pmcw.ena)
- /* Nothing to do. */
- return;
+ goto out_unlock;
ret = cio_disable_subchannel(sch);
if (ret != -EBUSY)
- /* Subchannel is disabled, we're done. */
- return;
- cdev->private->state = DEV_STATE_QUIESCE;
+ goto out_unlock;
if (cdev->handler)
- cdev->handler(cdev, cdev->private->intparm,
- ERR_PTR(-EIO));
- ret = ccw_device_cancel_halt_clear(cdev);
- if (ret == -EBUSY) {
- ccw_device_set_timeout(cdev, HZ/10);
- wait_event(cdev->private->wait_q, dev_fsm_final_state(cdev));
+ cdev->handler(cdev, cdev->private->intparm, ERR_PTR(-EIO));
+ while (ret == -EBUSY) {
+ cdev->private->state = DEV_STATE_QUIESCE;
+ ret = ccw_device_cancel_halt_clear(cdev);
+ if (ret == -EBUSY) {
+ ccw_device_set_timeout(cdev, HZ/10);
+ spin_unlock_irq(sch->lock);
+ wait_event(cdev->private->wait_q,
+ cdev->private->state != DEV_STATE_QUIESCE);
+ spin_lock_irq(sch->lock);
+ }
+ ret = cio_disable_subchannel(sch);
}
- cio_disable_subchannel(sch);
+out_unlock:
+ spin_unlock_irq(sch->lock);
}

static int device_is_disconnected(struct ccw_device *cdev)
Index: quilt-2.6/drivers/s390/cio/device_fsm.c
===================================================================
--- quilt-2.6.orig/drivers/s390/cio/device_fsm.c 2009-11-13 16:08:21.000000000 +0100
+++ quilt-2.6/drivers/s390/cio/device_fsm.c 2009-11-13 16:08:22.000000000 +0100
@@ -911,10 +911,7 @@
ccw_device_quiesce_done(struct ccw_device *cdev, enum dev_event dev_event)
{
ccw_device_set_timeout(cdev, 0);
- if (dev_event == DEV_EVENT_NOTOPER)
- cdev->private->state = DEV_STATE_NOT_OPER;
- else
- cdev->private->state = DEV_STATE_OFFLINE;
+ cdev->private->state = DEV_STATE_NOT_OPER;
wake_up(&cdev->private->wait_q);
}

@@ -924,17 +921,11 @@
int ret;

ret = ccw_device_cancel_halt_clear(cdev);
- switch (ret) {
- case 0:
- cdev->private->state = DEV_STATE_OFFLINE;
- wake_up(&cdev->private->wait_q);
- break;
- case -ENODEV:
+ if (ret == -EBUSY) {
+ ccw_device_set_timeout(cdev, HZ/10);
+ } else {
cdev->private->state = DEV_STATE_NOT_OPER;
wake_up(&cdev->private->wait_q);
- break;
- default:
- ccw_device_set_timeout(cdev, HZ/10);
}
}