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[S390] dasd: fix locking in __dasd_device_process_final_queue

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After setting the status of the cqr and releasing the lock for the
block cqr queue, we call the cqr callback function, which will usually
just trigger the dasd_block_tasklet. But when the tasklet is already
running the cqr might be processed before we invoke the callback
function. In rare cases the callback pointer may already be invalid
by the time we want to call it, which will result in a panic.
Solution: Call the callback function first and then release the lock.

Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Stefan Weinhuber 2008-02-19 15:29:27 +01:00 committed by Martin Schwidefsky
parent 11ab244c9f
commit 03513bccad
1 changed files with 6 additions and 6 deletions
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12
drivers/s390/block/dasd.c
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@ -1149,12 +1149,14 @@ static void __dasd_device_process_final_queue(struct dasd_device *device,
{
struct list_head *l, *n;
struct dasd_ccw_req *cqr;
struct dasd_block *block;
list_for_each_safe(l, n, final_queue) {
cqr = list_entry(l, struct dasd_ccw_req, devlist);
list_del_init(&cqr->devlist);
if (cqr->block)
spin_lock_bh(&cqr->block->queue_lock);
block = cqr->block;
if (block)
spin_lock_bh(&block->queue_lock);
switch (cqr->status) {
case DASD_CQR_SUCCESS:
cqr->status = DASD_CQR_DONE;
@ -1172,15 +1174,13 @@ static void __dasd_device_process_final_queue(struct dasd_device *device,
cqr, cqr->status);
BUG();
}
if (cqr->block)
spin_unlock_bh(&cqr->block->queue_lock);
if (cqr->callback != NULL)
(cqr->callback)(cqr, cqr->callback_data);
if (block)
spin_unlock_bh(&block->queue_lock);
}
}
/*
* Take a look at the first request on the ccw queue and check
* if it reached its expire time. If so, terminate the IO.