Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner field

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner field
Date	2016-05-18 13:10 +0200
Message-ID	<rA7wt-1ja-1@gated-at.bofh.it> (permalink)
References	(5 earlier) <rzpF8-6Wo-9@gated-at.bofh.it> <rzrxf-85I-21@gated-at.bofh.it> <rzuY9-1Ei-1@gated-at.bofh.it> <rzSH8-aP-19@gated-at.bofh.it> <rzTa9-mb-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tue, May 17, 2016 at 12:46:07PM -0700, Paul E. McKenney wrote:
> Actually, if you show a case where this makes a visible system-wide
> difference, you could create a set of primitives for #1 below.  Have
> a compiler version check, and if it is an old compiler, map them to
> READ_ONCE() and WRITE_ONCE(), otherwise as follows, though preferably
> with better names:
> 
> #define READ_NOTEAR(x) __atomic_load_n(&(x), __ATOMIC_RELAXED)
> #define WRITE_NOTEAR(x, v) __atomic_store_n(&(x), (v), __ATOMIC_RELAXED)
> 
> The ambiguity between "no tear" and "not ear" should help motivate a
> better choice of name.

Alternatively, could we try and talk to our GCC friends to make sure GCC
doesn't tear loads/stores irrespective of what the C language spec
allows?

Thread

Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field Peter Zijlstra <peterz@infradead.org> - 2016-05-13 17:10 +0200
  Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field Peter Hurley <peter@hurleysoftware.com> - 2016-05-13 20:00 +0200
    Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field Peter Zijlstra <peterz@infradead.org> - 2016-05-16 13:20 +0200
      Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-05-16 14:20 +0200
        Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field Peter Hurley <peter@hurleysoftware.com> - 2016-05-16 16:20 +0200
          Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-05-16 19:30 +0200
            Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field Peter Hurley <peter@hurleysoftware.com> - 2016-05-17 21:50 +0200
              Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field Peter Hurley <peter@hurleysoftware.com> - 2016-05-17 22:00 +0200
          Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field Peter Zijlstra <peterz@infradead.org> - 2016-05-16 20:00 +0200
            Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field Peter Hurley <peter@hurleysoftware.com> - 2016-05-17 21:20 +0200
              Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-05-17 21:50 +0200
                Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field Peter Zijlstra <peterz@infradead.org> - 2016-05-18 13:10 +0200
                Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field Waiman Long <waiman.long@hpe.com> - 2016-05-18 18:00 +0200
                Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-05-18 19:30 +0200
                Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-05-18 19:30 +0200
                Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field Peter Zijlstra <peterz@infradead.org> - 2016-05-19 11:10 +0200
                Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner  field "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-05-19 15:50 +0200

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