From f71ad62a264a89cb1952df0c92b167005de8d1b0 Mon Sep 17 00:00:00 2001 From: Michael Holzheu Date: Fri, 30 May 2008 10:03:25 +0200 Subject: [PATCH] [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 Signed-off-by: Martin Schwidefsky --- drivers/s390/char/tape_block.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/s390/char/tape_block.c b/drivers/s390/char/tape_block.c index ddc4a114e7f4..95da72bc17e8 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); -- 2.20.1