This bug impacts all versions of the kernel that I have looked at
including 2.4.18 and above. It probably impacts many other versions as
well.
hdparm -X issues a drive command ioctl which eventually issue a command
to the drive bypassing all of the normal locking. The net effect is
that a command can be set to the drive when the drive is not ready.
Some drives lock up when this happens.
The call chain is
ide_ioctl calls
ide_cmd_ioctl
If the command is a set features to change the communications speed,
after the command is complete, ide_cmd_ioctl calls
ide_set_xfer_rate
ide_set_xfer_rate then calls drive->speedproc.
Most speedprocs then call ide_config_drive_speed
ide_config_drive_speed issue a set features command. and busy waits on it.
The easiest fix is to probably modify execute_drive_command to update
drive->current_speed when it issues the appropriate SET FEATURES
command, and then have ide_config_drive_speed do nothing if speed ==
current_speed.
I did a much bigger modification that handles changing drive speed
specially and immediately. I'll make patches for either one, but I
wanted to get some opinions before I did so.
Ross