How to view pending SCSI requests?

If the PC sends a request to read a sector on an optical disc, which turns out to be unreadable, the drive deadlocks the program into responselessness and motionlessness, until it returns the sector or an error. During the time the program is locked by the drive, which makes the program effectively a slave, how can I see the pending SCSI request with details such as read retry count and requested LBA?