Hello, Bart.

On Wed, Feb 07, 2018 at 05:27:10PM +0000, Bart Van Assche wrote:

Even with the above change I think that there is still a race between the
code that handles timer resets and the completion handler. Anyway, the test

Can you elaborate the scenario a bit further?  If you're referring to
lost completions, we've always had that and while we can try to close
that hole too, I don't think it's a critical issue.

with which I triggered these races is as follows:
- Start from what will become kernel v4.16-rc1 and apply the patch that adds
  SRP over RoCE support to the ib_srpt driver. See also the "[PATCH v2 00/14]
  IB/srpt: Add RDMA/CM support" patch series
  (https://www.spinics.net/lists/linux-rdma/msg59589.html).
- Apply my patch series that fixes a race between the SCSI error handler and
  SCSI transport recovery.
- Apply my patch series that improves the stability of the SCSI target core
  (LIO).
- Build and install that kernel.
- Clone the following repository: https://github.com/bvanassche/srp-test.
- Run the following test:
  while true; do srp-test/run_tests -c -t 02-mq; done
- While the test is running, check whether or not something weird happens.
  Sometimes I see that scsi_times_out() crashes. Sometimes I see while running
  this test that a soft lockup is reported inside blk_mq_do_dispatch_ctx().

If you want I can share the tree on github that I use myself for my tests.

Heh, that's quite a bit.  I'll take up on that git tree later but for
now I'd really appreciate if you can test the patch.

Thank you very much.

-- 
tejun