On 10/28/14 18:39, Christoph Hellwig wrote:
On Tue, Oct 28, 2014 at 10:05:32AM +0100, Bart Van Assche wrote:
I might be missing some background information here, but it's not clear to
me why the function like scsi_block_when_processing_errors() was introduced
some time ago. What if immediately after error handling has finished a new
request is queued that kicks the error handler again before the caller of
scsi_block_when_processing_errors() has finished the actions that should
not occur concurrently with error handling ? Has it already been considered
to introduce a mutex to serialize error handling and activity that should
not occur concurrently with error handling ?
I've not looked into changing the conditions, but your questions are
good ones. I'd like to go even further and ask the question of what
we try to protect here. For SG_SCSI_RESET the answer is that we want
to enforce a single outstanding TMF, as require by old parallel SCSI HBAs,
and possible by various drivers. I don't quite understand why we check
the EH state before executing other ioctl, though. Even more confusing
is that some driver like st.c and sg.c only enforce this on some ioctls.
Changing the exclusion rules isn't in the scope of this series, but if
you interested in looking into this series I'd be happy if we get the
ball on it rolling.
Hello Christoph,
As you know I'm working on several different projects simultaneously so
I'm not sure I will be able to free up some time soon to work on this. I
will add this on my to-do list but if anyone else would like to start
working on this that would be welcome.
Bart.
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