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Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option

From "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Newsgroups linux.kernel
Subject Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option
Date 2017-07-26 17:50 +0200
Message-ID <u7wJr-2ak-5@gated-at.bofh.it> (permalink)
References (5 earlier) <u7ddM-6sM-5@gated-at.bofh.it> <u7dQv-6W7-47@gated-at.bofh.it> <u7eCV-7wj-77@gated-at.bofh.it> <u7fpf-86t-19@gated-at.bofh.it> <u7qXo-6Yw-13@gated-at.bofh.it>
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On Wed, Jul 26, 2017 at 10:36:46AM +0100, Will Deacon wrote:
> On Tue, Jul 25, 2017 at 02:19:26PM -0700, Paul E. McKenney wrote:
> > Some architectures are less precise than others in tracking which
> > CPUs are running a given process due to ASIDs, though this is
> > thought to be a non-problem:
> > 
> > 	https://marc.info/?l=linux-arch&m=126716090413065&w=2
> > 	https://marc.info/?l=linux-arch&m=126716262815202&w=2
> > 
> > Thoughts?
> 
> On arm64, we *never* touch mm_cpumask, so it will always be empty. The only
> thing we could potentially use it for is non-broadcast TLB invalidation if
> the mm was only active on a single CPU, but when I implemented that we
> pretty much never hit that case. I was hoping fork()+exec() would trigger it
> (e.g. scripts), but the scheduler treats both of those as rebalancing points
> so the temporary ASID before the exec always has two CPUs set in its mask.

OK, so it sounds like we should ignore ->mm_cpumask except possibly
for an architecture-specific optimization, and rely solely on ->mm
in the absence of such optimizations, right?

							Thanx, Paul

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[PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 00:00 +0200
  Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Boqun Feng <boqun.feng@gmail.com> - 2017-07-25 06:30 +0200
    Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 18:30 +0200
  Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2017-07-25 15:20 +0200
    Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 18:50 +0200
  Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-25 18:40 +0200
    Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 18:50 +0200
      Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-25 19:10 +0200
        Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 19:20 +0200
          Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-25 21:00 +0200
            Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 21:40 +0200
              Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-25 22:30 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 23:20 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-26 00:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2017-07-26 00:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2017-07-26 00:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 02:10 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-26 09:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 17:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2017-07-26 20:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 20:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2017-07-26 22:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 23:20 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 03:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2017-07-27 14:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 16:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 12:30 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 17:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 11:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 12:20 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Will Deacon <will.deacon@arm.com> - 2017-07-27 12:30 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 15:20 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 02:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-26 09:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 17:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 10:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 15:10 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 15:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 16:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 16:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 16:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 16:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 17:30 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Boqun Feng <boqun.feng@gmail.com> - 2017-07-27 16:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 16:20 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Boqun Feng <boqun.feng@gmail.com> - 2017-07-27 16:30 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 16:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Will Deacon <will.deacon@arm.com> - 2017-07-27 16:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Boqun Feng <boqun.feng@gmail.com> - 2017-07-27 16:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 17:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Will Deacon <will.deacon@arm.com> - 2017-07-26 11:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 17:50 +0200
              Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 12:20 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 15:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 15:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 16:40 +0200

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