Re: Use case for TASKS_RCU

From	Steven Rostedt <rostedt@goodmis.org>
Newsgroups	linux.kernel
Subject	Re: Use case for TASKS_RCU
Date	2017-05-23 21:50 +0200
Message-ID	<tKnYC-7Kl-9@gated-at.bofh.it> (permalink)
References	(4 earlier) <tIQim-2MD-21@gated-at.bofh.it> <tIQLo-3eE-15@gated-at.bofh.it> <tIR4J-3uF-15@gated-at.bofh.it> <tIVrH-6qG-7@gated-at.bofh.it> <tK5yF-458-3@gated-at.bofh.it>
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On Mon, 22 May 2017 17:00:36 -0700
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:

> > 
> > Hmmm...  The goal is to make sure that any task that was preempted
> > or running at a given point in time passes through a voluntary
> > context switch (or userspace execution, or, ...).
> > 
> > What is the simplest way to get this job done?  To Ingo's point, I
> > bet that there is a simpler way than the current TASKS_RCU
> > implementation.
> > 
> > Ingo, if I make it fit into 100 lines of code, would you be OK with
> > it? I probably need a one-line hook at task-creation time and
> > another at task-exit time, if that makes a difference.  
> 
> And please see below for such a patch, which does add (just barely)
> fewer than 100 lines net.
> 
> Unfortunately, it does not work, as I should have known ahead of time
> from the dyntick-idle experience.  Not all context switches go through
> context_switch().  :-/

Wait. What context switch doesn't go through a context switch? Or do
you mean a user/kernel context switch?

-- Steve

> 
> I believe this is fixable, more or less like dyntick-idle's
> half-interrupts were fixable, but it will likely be a few days.  Not
> clear whether the result will be simpler than current TASKS_RCU, but
> there is only one way to find out.  ;-)
>

Thread

Use case for TASKS_RCU "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-15 20:30 +0200
  Re: Use case for TASKS_RCU Steven Rostedt <rostedt@goodmis.org> - 2017-05-15 20:50 +0200
    Re: Use case for TASKS_RCU "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-15 22:20 +0200
  Re: Use case for TASKS_RCU Ingo Molnar <mingo@kernel.org> - 2017-05-16 08:30 +0200
    Re: Use case for TASKS_RCU "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-16 14:30 +0200
      Re: Use case for TASKS_RCU Steven Rostedt <rostedt@goodmis.org> - 2017-05-16 15:10 +0200
        Re: Use case for TASKS_RCU Masami Hiramatsu <mhiramat@kernel.org> - 2017-05-24 11:40 +0200
      Re: Use case for TASKS_RCU Ingo Molnar <mingo@kernel.org> - 2017-05-19 08:30 +0200
        Re: Use case for TASKS_RCU "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-19 15:40 +0200
          Re: Use case for TASKS_RCU Steven Rostedt <rostedt@goodmis.org> - 2017-05-19 16:10 +0200
            Re: Use case for TASKS_RCU Steven Rostedt <rostedt@goodmis.org> - 2017-05-19 16:30 +0200
              Re: Use case for TASKS_RCU "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-19 21:10 +0200
                Re: Use case for TASKS_RCU "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-23 02:10 +0200
                Re: Use case for TASKS_RCU Steven Rostedt <rostedt@goodmis.org> - 2017-05-23 07:30 +0200
                Re: Use case for TASKS_RCU "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-23 17:40 +0200
                Re: Use case for TASKS_RCU Steven Rostedt <rostedt@goodmis.org> - 2017-05-23 21:50 +0200
                Re: Use case for TASKS_RCU "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-23 22:10 +0200
                Re: Use case for TASKS_RCU Steven Rostedt <rostedt@goodmis.org> - 2017-05-23 22:50 +0200
                Re: Use case for TASKS_RCU "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-23 23:20 +0200

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