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Re: Query regarding synchronize_sched_expedited and resched_cpu

From "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Newsgroups linux.kernel
Subject Re: Query regarding synchronize_sched_expedited and resched_cpu
Date 2017-09-21 17:40 +0200
Message-ID <usbK3-2QA-35@gated-at.bofh.it> (permalink)
References (5 earlier) <ur6W7-7F-27@gated-at.bofh.it> <ur75M-b2-41@gated-at.bofh.it> <ur75M-b2-39@gated-at.bofh.it> <ur7yO-mI-9@gated-at.bofh.it> <usabh-1IE-43@gated-at.bofh.it>
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On Thu, Sep 21, 2017 at 03:57:49PM +0200, Peter Zijlstra wrote:
> On Mon, Sep 18, 2017 at 09:55:27AM -0700, Paul E. McKenney wrote:
> > On Mon, Sep 18, 2017 at 12:29:31PM -0400, Steven Rostedt wrote:
> > > On Mon, 18 Sep 2017 09:24:12 -0700
> > > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
> > > 
> > > 
> > > > As soon as I work through the backlog of lockdep complaints that
> > > > appeared in the last merge window...  :-(
> > > > 
> > > > sparse_irq_lock, I am looking at you!!!  ;-)
> 
> That one is a false positive and I have send patches to address.

I did try them out, and they work fine for me when lockdep is enabled.
I get build failures if lockdep is not enabled.  Things are a bit crazy
here, so I have not had a chance to try to fix them, though it should
not be a big deal (easy for me to say!).

> > > I just hit one too, and decided to write a patch to show a chain of 3
> > > when applicable.
> > > 
> > > For example:
> > > 
> > >  Chain exists of:
> > >    cpu_hotplug_lock.rw_sem --> smpboot_threads_lock --> (complete)&self->parked
> > > 
> > >   Possible unsafe locking scenario by crosslock:
> > > 
> > >         CPU0                    CPU1                    CPU2
> > >         ----                    ----                    ----
> > >    lock(smpboot_threads_lock);
> > >    lock((complete)&self->parked);
> > >                                 lock(cpu_hotplug_lock.rw_sem);
> > >                                 lock(smpboot_threads_lock);
> > >                                                        lock(cpu_hotplug_lock.rw_sem);
> > >                                                        unlock((complete)&self->parked);
> > > 
> > >   *** DEADLOCK ***
> > > 
> > > :-)
> > 
> > Nice!!!
> 
> That one looks like the watchdog thing, and Thomas was poking at that.

For whatever it is worth, I am still chasing lost-timer bugs.  I now know
of a large number of things that are not the cause of the problem.  :-/

							Thanx, Paul

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Thread

Query regarding synchronize_sched_expedited and resched_cpu Neeraj Upadhyay <neeraju@codeaurora.org> - 2017-09-15 13:20 +0200
  Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-17 03:10 +0200
    Re: Query regarding synchronize_sched_expedited and resched_cpu Neeraj Upadhyay <neeraju@codeaurora.org> - 2017-09-17 08:10 +0200
      Re: Query regarding synchronize_sched_expedited and resched_cpu Steven Rostedt <rostedt@goodmis.org> - 2017-09-18 17:20 +0200
        Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-18 18:10 +0200
          Re: Query regarding synchronize_sched_expedited and resched_cpu Steven Rostedt <rostedt@goodmis.org> - 2017-09-18 18:20 +0200
            Re: Query regarding synchronize_sched_expedited and resched_cpu Steven Rostedt <rostedt@goodmis.org> - 2017-09-18 18:30 +0200
              Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-18 19:00 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-19 02:00 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu Steven Rostedt <rostedt@goodmis.org> - 2017-09-19 03:30 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-19 04:30 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu Byungchul Park <byungchul.park@lge.com> - 2017-09-19 04:00 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu Byungchul Park <byungchul.park@lge.com> - 2017-09-19 04:10 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-19 04:40 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu Byungchul Park <byungchul.park@lge.com> - 2017-09-19 04:50 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-19 06:10 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu Boqun Feng <boqun.feng@gmail.com> - 2017-09-19 07:40 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu Mike Galbraith <efault@gmx.de> - 2017-09-19 08:20 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu Byungchul Park <byungchul.park@lge.com> - 2017-09-19 09:00 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-19 15:50 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu Peter Zijlstra <peterz@infradead.org> - 2017-09-21 16:00 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-21 17:40 +0200
              Re: Query regarding synchronize_sched_expedited and resched_cpu Byungchul Park <byungchul.park@lge.com> - 2017-09-19 04:00 +0200
            Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-18 18:30 +0200
              Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-19 17:40 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu Steven Rostedt <rostedt@goodmis.org> - 2017-09-19 18:00 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-19 18:20 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu Peter Zijlstra <peterz@infradead.org> - 2017-09-21 16:10 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-21 18:10 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu Peter Zijlstra <peterz@infradead.org> - 2017-09-21 18:40 +0200
                Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-21 18:50 +0200
        Re: Query regarding synchronize_sched_expedited and resched_cpu Peter Zijlstra <peterz@infradead.org> - 2017-09-21 16:00 +0200
          Re: Query regarding synchronize_sched_expedited and resched_cpu "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-21 17:40 +0200
            Re: Query regarding synchronize_sched_expedited and resched_cpu Peter Zijlstra <peterz@infradead.org> - 2017-09-21 18:20 +0200
          Re: Query regarding synchronize_sched_expedited and resched_cpu Steven Rostedt <rostedt@goodmis.org> - 2017-09-21 17:50 +0200

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