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

From: Tejun Heo
Date: Wed Apr 27 2005 - 06:51:57 EST

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?


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