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    SubjectRe: [patch 1/3] rtmutex: Add missing deadlock check
    On Tue, May 13, 2014 at 04:20:41PM -0400, Steven Rostedt wrote:
    > On Tue, 13 May 2014 21:42:54 +0200 (CEST)
    > Thomas Gleixner <tglx@linutronix.de> wrote:
    >
    > > On Tue, 13 May 2014, Peter Zijlstra wrote:
    > > >
    > > > Now, if you and Steve get this sorted, nothing really happened except
    > > > that Thomas got grumpy, which is entirely normal, what else would he be?
    > > > :-)
    > >
    > > Who is that grumpy Thomas dude, should I know him?

    ;-) ;-) ;-)

    > > Lai, Steven,
    > >
    > > before you waste lots of time on the tester, I want to look at it
    > > whether we can simplify it or even rewrite it from scratch. I glanced
    > > at it today and I really can't remember what kind of substances were
    > > involved when I wrote this almost a decade ago.
    >
    > Thank God. /me removes the ton of trace_printk()s in the code as well
    > as all the trace_marker.write("%s" %(line)) from the test to figure out
    > what was going on.
    >
    > >
    > > The whole schedule_rt_mutex mechanism was mostly done to create
    > > controlled lock stealing scenarios and deal with the BKL
    > > oddities.
    > >
    > > With Lai's simplification and the demise of BKL I'm quite sure we do
    > > not need it anymore.
    > >
    > > So we can just get rid of the complexity in schedule_rt_mutex() and
    > > replace it with a simple:
    > >
    > > while (!td->continue)
    > > schedule();
    > >
    > > That would also make the teardown and reset of the whole thing
    > > manageable. Right now it's easy to create a situation where unrolling
    > > stuff gets almost impossible except by pushing the reset button.
    > >
    > > The state readouts can be done directly via the rtmutexes and the task
    > > structs.
    > >
    > > Thoughts?
    > >
    >
    > What about having a module that creates a bunch of threads and forces
    > all the scenarios that we want to test? Wouldn't it be easier to do
    > than to have a userspace interface to dictate commands to the kernel?

    I second this approach! The kernel environment makes it -much- easier
    to force races and other conditions, which turns into much simpler and
    more effective tests.

    Thanx, Paul



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