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Re: There is a Tasks RCU stall warning

From "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Newsgroups linux.kernel
Subject Re: There is a Tasks RCU stall warning
Date 2017-04-11 23:50 +0200
Message-ID <tvbPH-471-7@gated-at.bofh.it> (permalink)
References <tvbmF-3WD-7@gated-at.bofh.it> <tvbG1-43u-3@gated-at.bofh.it> <tvbG1-43u-1@gated-at.bofh.it> <tvbG1-43u-7@gated-at.bofh.it>
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On Tue, Apr 11, 2017 at 05:39:00PM -0400, Steven Rostedt wrote:
> On Tue, 11 Apr 2017 17:34:47 -0400
> Steven Rostedt <rostedt@goodmis.org> wrote:
> 
> > On Tue, 11 Apr 2017 17:31:33 -0400
> > Steven Rostedt <rostedt@goodmis.org> wrote:
> > 
> > > The thread gets created when I enable the benchmark tracepoint. It just
> > > so happens that my test enables *all* tracepoints, which would of
> > > course include this one as well.
> > > 
> > > I'll have to look at this code to see why it is getting missed.  
> > 
> > Yep, this thread never goes to sleep, but will call cond_resched()
> > periodically. This keeps rcu_tasks() from finishing.
> > 
> > Should I add a direct "schedule()" in there instead of a
> > cond_resched(), or do you think rcu_tasks should have cond_resched() be
> > a quiescent state as well?
> 
> Actually, I believe this found a bug in my trace_event benchmark
> thread. On a preempt kernel, cond_resched() is a nop and expects to
> only be preempted. Calling schedule() directly should fix everything. I
> shouldn't depend on cond_resched() here.

Works for me!

Hopefully it will also work for your computer.  :-)

And whew!  Glad to see that the stall warnings worked!

							Thanx, Paul

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Thread

There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-11 23:20 +0200
  Re: There is a Tasks RCU stall warning Steven Rostedt <rostedt@goodmis.org> - 2017-04-11 23:30 +0200
    Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-11 23:40 +0200
  Re: There is a Tasks RCU stall warning Steven Rostedt <rostedt@goodmis.org> - 2017-04-11 23:40 +0200
    Re: There is a Tasks RCU stall warning Steven Rostedt <rostedt@goodmis.org> - 2017-04-11 23:40 +0200
      Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-11 23:50 +0200
        Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-12 00:00 +0200
          Re: There is a Tasks RCU stall warning Steven Rostedt <rostedt@goodmis.org> - 2017-04-12 00:20 +0200
            Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-12 01:10 +0200
              Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-12 01:10 +0200
                Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-12 01:20 +0200
                Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-12 05:30 +0200
                Re: There is a Tasks RCU stall warning Steven Rostedt <rostedt@goodmis.org> - 2017-04-12 15:20 +0200
                Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-12 16:30 +0200
                Re: There is a Tasks RCU stall warning Steven Rostedt <rostedt@goodmis.org> - 2017-04-12 16:50 +0200
                Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-12 17:20 +0200
                Re: There is a Tasks RCU stall warning Steven Rostedt <rostedt@goodmis.org> - 2017-04-12 18:00 +0200
                Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-12 18:30 +0200
                Re: There is a Tasks RCU stall warning Steven Rostedt <rostedt@goodmis.org> - 2017-04-12 18:50 +0200
                Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-12 16:50 +0200
                Re: There is a Tasks RCU stall warning Steven Rostedt <rostedt@goodmis.org> - 2017-04-12 17:00 +0200
                Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-12 18:30 +0200
                Re: There is a Tasks RCU stall warning Steven Rostedt <rostedt@goodmis.org> - 2017-04-12 19:00 +0200
                Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-12 19:10 +0200
                Re: There is a Tasks RCU stall warning Steven Rostedt <rostedt@goodmis.org> - 2017-04-12 19:20 +0200
                Re: There is a Tasks RCU stall warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-04-12 22:10 +0200
        Re: There is a Tasks RCU stall warning Steven Rostedt <rostedt@goodmis.org> - 2017-04-12 00:00 +0200
  Re: There is a Tasks RCU stall warning Steven Rostedt <rostedt@goodmis.org> - 2017-04-11 23:40 +0200

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