James Bottomley wrote:
On Thu, 2005-06-02 at 20:31 +0300, Liran Schour wrote:
I am developing a new SCSI upper layer driver. (Object based SCSI device)
I noticed that scsi_do_req execute commands in LIFO order (add new commands
to the head of the Q).
This behavior can cause a starvation of commands (or at least long delays).
What is the proper solution to this?
Well, to use the proper interfaces.
scsi_do_req is deprecated, so don't use it. scsi_wait_req is its
replacement. Note: they're only really intended to allow ULDs to
execute commands that are necessary for controlling the device (that's
why they go at the head of the queue). Block commands are executed in
order using ULD init_command() (or REQ_BLOCK_PC).
Hm, st/osst/sg use scsi_do_req(), so should we consider those drivers
broken in async mode? Apparently, a user in this mode could write not
what he/she intented, the order could be wrong. Or do I miss something?
Vlad
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