From 1c1e093cbf6d3a7576ba0bd10363362a1c5c74ee Mon Sep 17 00:00:00 2001 From: Stefan Weinhuber Date: Wed, 12 May 2010 09:32:11 +0200 Subject: [PATCH] [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: Signed-off-by: Stefan Weinhuber Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- drivers/s390/block/dasd.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c index acf222f..fa2339c 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); -- 2.7.4