diff options
| author | Michael Holzheu <holzheu@de.ibm.com> | 2008-05-30 10:03:25 +0200 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2008-05-30 10:03:33 +0200 |
| commit | f71ad62a264a89cb1952df0c92b167005de8d1b0 (patch) | |
| tree | de173ab5f138204d5ba5458de249c39e5faecdbd | |
| parent | 97195d6b411fec8e33aa55b6a7c3dde7984d65ca (diff) | |
[S390] tape: Fix race condition in tape block device driver
Due to incorrect function call sequence it can happen that a tape block
request is finished before the request is taken from the block request queue.
The following sequence leads to that condition:
* tapeblock_start_request() -> start CCW program
* Request finishes -> IO interrupt
* tapeblock_end_request()
* end_that_request_last()
If blkdev_dequeue_request() has not been called before end_that_request_last(),
a kernel bug is triggered in end_that_request_last() because the request is
still queued. To solve that problem blkdev_dequeue_request() has to be called
before starting the CCW program.
Signed-off-by: Michael Holzheu <holzheu@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
| -rw-r--r-- | drivers/s390/char/tape_block.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/s390/char/tape_block.c b/drivers/s390/char/tape_block.c index ddc4a114e7f..95da72bc17e 100644 --- a/drivers/s390/char/tape_block.c +++ b/drivers/s390/char/tape_block.c @@ -179,11 +179,11 @@ tapeblock_requeue(struct work_struct *work) { tapeblock_end_request(req, -EIO); continue; } + blkdev_dequeue_request(req); + nr_queued++; spin_unlock_irq(&device->blk_data.request_queue_lock); rc = tapeblock_start_request(device, req); spin_lock_irq(&device->blk_data.request_queue_lock); - blkdev_dequeue_request(req); - nr_queued++; } spin_unlock_irq(&device->blk_data.request_queue_lock); atomic_set(&device->blk_data.requeue_scheduled, 0); |