linux-kernel - Re: [PATCH] tools: selftests - create a separate hotplug target

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Date:	Fri, 27 Jun 2014 12:45:52 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	shuah.kh@...sung.com
Cc:	gregkh@...uxfoundation.org, keescook@...omium.org,
	michael@...erman.id.au, fweisbec@...il.com,
	benh@...nel.crashing.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tools: selftests - create a separate hotplug target

On Fri, 27 Jun 2014 11:10:37 -0600 Shuah Khan <shuah.kh@...sung.com> wrote:

> On 06/26/2014 03:51 PM, Andrew Morton wrote:
> > On Thu, 26 Jun 2014 14:33:56 -0600 Shuah Khan <shuah.kh@...sung.com> wrote:
> >
> >> On some systems, hotplug tests could hang forever waiting for cpu and
> >> memory to be ready to be offlined. A special hotplug target is created,
> >> which will help run non-hotplug tests and run hotplug tests as a special
> >> case. Individual hotplug tests can still be run as a special target
> >> targeted for a single subsystem.
> >
> > This is a bit sad.  The general philosophy with selftests is that they
> > should run to completion even if the kernel/hardware which they are
> > testing isn't available - they should work it out for themselves.
> >
> > But that's obviously a problem with hotplug.  And with networking or
> > anything else which needs external action.
> >
> > On the other hand, networking has loopback and the kernel supports cpu
> > hotplug simulation via procfs.  So perhaps the cpu and memory hotplug
> > tests should be redone so they do the plug/unplug injection themselves,
> > so they can run without external intervention?
> 
> Changing/running the tests in a safe mode (least possibility of hang)
> mode is another option. This way the tests are run in normal mode with
> reduced scope. Memory hotplug test has the ratio option and when I
> specified low ratio 1-5%, it completed in a few seconds.
> 
> cpu-hotplug test will require changes. I am working on a change to
> offline a user specified # of cpus instead offlining all hotpluggable
> cpus and then onlining them again at the end of the test.
> 
> When all selftests are run, safe mode hotplug tests will be run.
> 
> Does this approach sound reasonable?

I don't know really.  You know more about this than I - what advantages
does the separate-make-target approach have over this approach?

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