Messages in this thread | | | Date | Tue, 13 May 2014 13:36:19 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [patch 1/3] rtmutex: Add missing deadlock check |
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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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