Re: [PATCH scsi-misc-2.6 01/04] scsi: make scsi_send_eh_cmnd use its own timer instead of scmd->eh_timeout

[Tejun Heo <htejun@gmail.com>]

  Hello, James.

James Bottomley wrote:
> On Wed, 2005-04-27 at 11:22 +0900, Tejun Heo wrote:
> 
>> * A command is passed to lldd and starts execution
>> * It times out.
>> * eh runs
>> * abort isn't implemented or fails
>> * eh issues eh cmd (TUL, STU...)
>> * The command miraculously & stupidly completes just now.
> 
> 
> This should be impossible.  The error handler API requirement is that
> the driver relinquish a command once it returns success from any error
> handling callback ... and if it never returns success, we simply offline
> the device and never use it again.  This is the principle behind the
> command reuse: we only try an additional command *after* error handling
> succeeds, so the error handler now owns the command absolutely.
> 

  Hmmm, yeah, it currently cannot happen, and if what you're describing 
is a requirement, everything should be okay.  But, I still think that 
using separate timer will be better as it won't add any overhead (with 
the change you proposed) and it makes the somewhat unobivous requirement 
go away.  Or at least add BUG_ON() test or something to make the 
requirement clear.

  What do you think?

  Thanks.

-- 
tejun