Bug 191471

Summary:	Mp2Sas and Mpt3Sas (now mpxsas) drivers are spinning forever in the IRQ handler under load condition
Product:	IO/Storage	Reporter:	Sinan Kaya (okaya)
Component:	SCSI	Assignee:	linux-scsi (linux-scsi)
Status:	NEW ---
Severity:	normal	CC:	cov, okaya, timur
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	4.7	Subsystem:
Regression:	No	Bisected commit-id:
Attachments:	Propsed fix

Description Sinan Kaya 2016-12-29 15:16:46 UTC

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.

Comment 1 Timur Tabi 2017-04-03 15:31:37 UTC

Created attachment 255737 [details]
Propsed fix