From: Michael Holzheu Date: Fri, 30 May 2008 08:03:25 +0000 (+0200) Subject: [S390] tape: Fix race condition in tape block device driver X-Git-Tag: v2.6.26-rc5~35^2~10 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f71ad62a264a89cb1952df0c92b167005de8d1b0;p=linux-2.6 [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 --- diff --git a/drivers/s390/char/tape_block.c b/drivers/s390/char/tape_block.c index ddc4a114e7..95da72bc17 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);