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authorStefan Weinhuber <wein@de.ibm.com>2010-05-12 09:32:11 +0200
committerMartin Schwidefsky <sky@mschwide.boeblingen.de.ibm.com>2010-05-12 09:32:26 +0200
commit1c1e093cbf6d3a7576ba0bd10363362a1c5c74ee (patch)
treea3970653539aa4a9b71536a204efbe7d5ba8ff07
parentcea0d767c29669bf89f86e4aee46ef462d2ebae8 (diff)
[S390] dasd: fix race between tasklet and dasd_sleep_on
The various dasd_sleep_on functions use a global wait queue when waiting for a cqr. The wait condition checks the status and devlist fields of the cqr to determine if it is safe to continue. This evaluation may return true, although the tasklet has not finished processing of the cqr and the callback function has not been called yet. When the callback is finally called, the data in the cqr may already be invalid. The sleep_on wait condition needs a safe way to determine if the tasklet has finished processing. Use the callback_data field of the cqr to store a token, which is set by the callback function itself. Cc: <stable@kernel.org> Signed-off-by: Stefan Weinhuber <wein@de.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
-rw-r--r--drivers/s390/block/dasd.c17
1 files changed, 10 insertions, 7 deletions
diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index acf222f91f5..fa2339cb168 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -37,6 +37,9 @@
*/
#define DASD_CHANQ_MAX_SIZE 4
+#define DASD_SLEEPON_START_TAG (void *) 1
+#define DASD_SLEEPON_END_TAG (void *) 2
+
/*
* SECTION: exported variables of dasd.c
*/
@@ -1472,7 +1475,10 @@ void dasd_add_request_tail(struct dasd_ccw_req *cqr)
*/
static void dasd_wakeup_cb(struct dasd_ccw_req *cqr, void *data)
{
- wake_up((wait_queue_head_t *) data);
+ spin_lock_irq(get_ccwdev_lock(cqr->startdev->cdev));
+ cqr->callback_data = DASD_SLEEPON_END_TAG;
+ spin_unlock_irq(get_ccwdev_lock(cqr->startdev->cdev));
+ wake_up(&generic_waitq);
}
static inline int _wait_for_wakeup(struct dasd_ccw_req *cqr)
@@ -1482,10 +1488,7 @@ static inline int _wait_for_wakeup(struct dasd_ccw_req *cqr)
device = cqr->startdev;
spin_lock_irq(get_ccwdev_lock(device->cdev));
- rc = ((cqr->status == DASD_CQR_DONE ||
- cqr->status == DASD_CQR_NEED_ERP ||
- cqr->status == DASD_CQR_TERMINATED) &&
- list_empty(&cqr->devlist));
+ rc = (cqr->callback_data == DASD_SLEEPON_END_TAG);
spin_unlock_irq(get_ccwdev_lock(device->cdev));
return rc;
}
@@ -1573,7 +1576,7 @@ static int _dasd_sleep_on(struct dasd_ccw_req *maincqr, int interruptible)
wait_event(generic_waitq, !(device->stopped));
cqr->callback = dasd_wakeup_cb;
- cqr->callback_data = (void *) &generic_waitq;
+ cqr->callback_data = DASD_SLEEPON_START_TAG;
dasd_add_request_tail(cqr);
if (interruptible) {
rc = wait_event_interruptible(
@@ -1652,7 +1655,7 @@ int dasd_sleep_on_immediatly(struct dasd_ccw_req *cqr)
}
cqr->callback = dasd_wakeup_cb;
- cqr->callback_data = (void *) &generic_waitq;
+ cqr->callback_data = DASD_SLEEPON_START_TAG;
cqr->status = DASD_CQR_QUEUED;
list_add(&cqr->devlist, &device->ccw_queue);