[Bug 191471] New: Mp2Sas and Mpt3Sas (now mpxsas) drivers are spinning forever in the IRQ handler under load condition

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=191471

            Bug ID: 191471
           Summary: Mp2Sas and Mpt3Sas (now mpxsas) drivers are spinning
                    forever in the IRQ handler under load condition
           Product: IO/Storage
           Version: 2.5
    Kernel Version: 4.7
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: SCSI
          Assignee: linux-scsi@vger.kernel.org
          Reporter: okaya@codeaurora.org
        Regression: No

When there are a lot of IO requests queued for the HW, the IRQ handler of the
mpxsas driver spins forever until all requests are serviced. 

Spinning in the IRQ handler forever is a bad design and causes stalls on the
other cores that is unrelated to this request.

A simple solution has been posted here but rejected by the maintainer as the
maintainer has been looking to offload only the slow path to task context.

https://patchwork.kernel.org/patch/7579951/

Further requests for details to resolve the issue has been unanswered.

Logging the issue here for awareness.

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