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Groups > linux.kernel > #1474502

Re: [RFC][PATCH] Fix a race between rwsem and the scheduler

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [RFC][PATCH] Fix a race between rwsem and the scheduler
Date 2016-09-01 17:40 +0200
Message-ID <scCfU-3EJ-35@gated-at.bofh.it> (permalink)
References (5 earlier) <sbYLv-1Qd-11@gated-at.bofh.it> <scdUe-2XV-15@gated-at.bofh.it> <sclyp-7Kc-23@gated-at.bofh.it> <scu8G-5sK-27@gated-at.bofh.it> <scB0u-2VS-5@gated-at.bofh.it>
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On Thu, Sep 01, 2016 at 10:17:57PM +0800, Boqun Feng wrote:
> On Thu, Sep 01, 2016 at 08:57:38AM +0200, Peter Zijlstra wrote:
> Could there be some code that relies on the full barrier semantics of
> schedule() to provide transitivity?

Could, sure, who knows. RCU might, although Paul typically sticks in
smp_mb just to be safe.

The kernel coming apart when you remove that sync would prove this
fairly quick though.

Like Ben said, it not coming apart doesn't prove anything. It coming
apart does however prove something, namely that it is required :-)

> IIUC, the Program Order Guarantee you stated before try_to_wake_up()
> only has ordering effect on wakers and wakees.

Right, the scheduler only does RCpc guarantees.

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Thread

[RFC][PATCH] Fix a race between rwsem and the scheduler Balbir Singh <bsingharora@gmail.com> - 2016-08-30 10:50 +0200
  Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Nicholas Piggin <npiggin@gmail.com> - 2016-08-30 11:20 +0200
  Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Peter Zijlstra <peterz@infradead.org> - 2016-08-30 14:20 +0200
    Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Oleg Nesterov <oleg@redhat.com> - 2016-08-30 15:10 +0200
      Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Peter Zijlstra <peterz@infradead.org> - 2016-08-30 16:20 +0200
        Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Oleg Nesterov <oleg@redhat.com> - 2016-08-30 19:00 +0200
          Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Peter Zijlstra <peterz@infradead.org> - 2016-08-30 20:40 +0200
            Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2016-08-30 23:30 +0200
              Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Peter Zijlstra <peterz@infradead.org> - 2016-08-31 09:20 +0200
                Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2016-08-31 13:40 +0200
              Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Peter Zijlstra <peterz@infradead.org> - 2016-08-31 15:40 +0200
                Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2016-08-31 23:50 +0200
                Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Balbir Singh <bsingharora@gmail.com> - 2016-09-01 08:50 +0200
                Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Peter Zijlstra <peterz@infradead.org> - 2016-09-01 09:00 +0200
                Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Boqun Feng <boqun.feng@gmail.com> - 2016-09-01 16:20 +0200
                Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Peter Zijlstra <peterz@infradead.org> - 2016-09-01 17:40 +0200
      Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2016-08-30 23:30 +0200
        Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Peter Zijlstra <peterz@infradead.org> - 2016-08-31 09:30 +0200
          Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2016-08-31 13:40 +0200
    Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Balbir Singh <bsingharora@gmail.com> - 2016-08-31 05:50 +0200
      Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Peter Zijlstra <peterz@infradead.org> - 2016-08-31 09:30 +0200
        Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Balbir Singh <bsingharora@gmail.com> - 2016-08-31 12:20 +0200
        Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2016-08-31 13:00 +0200
        Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Alexey Kardashevskiy <aik@ozlabs.ru> - 2016-09-01 03:50 +0200
          Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Alexey Kardashevskiy <aik@ozlabs.ru> - 2016-09-01 14:20 +0200
  Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Oleg Nesterov <oleg@redhat.com> - 2016-08-30 15:00 +0200
    Re: [RFC][PATCH] Fix a race between rwsem and the scheduler Balbir Singh <bsingharora@gmail.com> - 2016-08-31 05:50 +0200

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