On Tue, Dec 09, 2008 at 09:26:08AM +0100, Joerg Dorchain wrote:
On Mon, Dec 08, 2008 at 04:59:38PM +0000, Andreas Bombe wrote:
The replacement for the unconditional sleep_on() in fd_motor_on() is a
complete_all() together with a INIT_COMPLETION() before the mod_timer()
call. It appears to me that fd_motor_on() might be called concurrently
and fd_select() does not guarantee mutual exclusivity in the case the
same drive gets selected again.
Selecting the same drive repeatly does not matter. The selected
drive is the one the next command or transfer applies to.
I think we're not talking about the same problem. If I were to use
complete() together with wait_for_completion() there would be a problem
if fd_motor_on() can get as far as wait_for_completion() while a
previous completion is yet uncompleted. This can not happen for
different drives, as the fd_select() would block. If it could happen
for the same drive, the complete() would allow only one task to
continue. The complete_all() takes care of that.
If requests are serialized for a drive so that there won't ever be two
running at the same time for certain (thinking about it, it's probable),
I could make it a simple complete(). It's hardly worth the risk,
however.
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