scsi: ipr: Fix abort path race condition

scsi: ipr: Fix abort path race condition

This fixes a race condition in the error handlomg paths of ipr. While a
command is outstanding to the adapter, it is placed on a pending queue
for the hrrq it is associated with, while holding the HRRQ lock. When a
command is completed, it is removed from the pending queue, under HRRQ
lock, and placed on a local list.  This list is then iterated through
without any locks and each command's done function is invoked, inside of
which, the command gets returned to the free list while grabbing the
HRRQ lock. This fixes two race conditions when commands have been
removed from the pending list but have not yet been added to the free
list. Both of these changes fix race conditions that could result in
returning success from eh_abort_handler and then later calling scsi_done
for the same request.

The first race condition is in ipr_cancel_op. It looks through each
pending queue to see if the command to be aborted is still outstanding
or not. Rather than looking on the pending queue, reverse the logic to
check to look for commands that are NOT on the free queue.  The second
race condition can occur when in ipr_wait_for_ops where we are waiting
for responses for commands we've aborted.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Reviewed-by: Wendy Xiong <wenxiong@linux.vnet.ibm.com>
Tested-by: Wendy Xiong <wenxiong@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>