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Re: [RFC patch 4/7] futex: Add support for attached futexes

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On Sun, 3 Apr 2016, Andy Lutomirski wrote:

> On Sun, Apr 3, 2016 at 2:57 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> > On Sat, 2 Apr 2016, Andy Lutomirski wrote:
> >
> >> On 04/02/2016 04:09 AM, Thomas Gleixner wrote:
> >> [omitted due to some Thunderbird bug, sigh]
> >>
> >> What happens if you mix attached an non-attached ops on the same futex?
> >
> > Not much. You might get an error code, sleep forever or the call will just
> > result in a NOP wasting cpu cycles. That's the same when you mix
> > shared/private operations on the same futex.
> 
> What's the workflow?
> 
> Can the creation of an attached futex fail due to memory allocation
> problems or any other reason?  If so, how does a library make sure it
> falls back to a normal futex safely?

Well, other operations on futexes can fail as well and the library or the
usage site has to take care of it. It's not that different.

> Why can't private futexes be attached by default?

We _can_ attach any futex - private or not - by default.

Thanks,

	tglx

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[RFC patch 0/7] futex: Add support for attached futexes Thomas Gleixner <tglx@linutronix.de> - 2016-04-02 13:20 +0200
  [RFC patch 1/7] futex: Provide helpers for hash bucket add/remove Thomas Gleixner <tglx@linutronix.de> - 2016-04-02 13:20 +0200
  [RFC patch 2/7] futex: Add some more function commentry Thomas Gleixner <tglx@linutronix.de> - 2016-04-02 13:20 +0200
  [RFC patch 5/7] perf/bench/futex-hash: Support for attached futexes Thomas Gleixner <tglx@linutronix.de> - 2016-04-02 13:20 +0200
  [RFC patch 4/7] futex: Add support for attached futexes Thomas Gleixner <tglx@linutronix.de> - 2016-04-02 13:20 +0200
    Re: [RFC patch 4/7] futex: Add support for attached futexes Peter Zijlstra <peterz@infradead.org> - 2016-04-02 18:30 +0200
      Re: [RFC patch 4/7] futex: Add support for attached futexes Thomas Gleixner <tglx@linutronix.de> - 2016-04-03 12:10 +0200
    Re: [RFC patch 4/7] futex: Add support for attached futexes Peter Zijlstra <peterz@infradead.org> - 2016-04-02 18:30 +0200
      Re: [RFC patch 4/7] futex: Add support for attached futexes Thomas Gleixner <tglx@linutronix.de> - 2016-04-02 20:10 +0200
    Re: [RFC patch 4/7] futex: Add support for attached futexes Andy Lutomirski <luto@kernel.org> - 2016-04-02 20:30 +0200
      Re: [RFC patch 4/7] futex: Add support for attached futexes Thomas Gleixner <tglx@linutronix.de> - 2016-04-03 12:00 +0200
        Re: [RFC patch 4/7] futex: Add support for attached futexes Andy Lutomirski <luto@amacapital.net> - 2016-04-03 15:20 +0200
          Re: [RFC patch 4/7] futex: Add support for attached futexes Thomas Gleixner <tglx@linutronix.de> - 2016-04-03 18:00 +0200
            Re: [RFC patch 4/7] futex: Add support for attached futexes Andy Lutomirski <luto@amacapital.net> - 2016-04-03 18:20 +0200
    Re: [RFC patch 4/7] futex: Add support for attached futexes Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2016-04-03 01:50 +0200
      Re: [RFC patch 4/7] futex: Add support for attached futexes Thomas Gleixner <tglx@linutronix.de> - 2016-04-03 12:10 +0200
    Re: [RFC patch 4/7] futex: Add support for attached futexes Ingo Molnar <mingo@kernel.org> - 2016-04-03 13:20 +0200
      Re: [RFC patch 4/7] futex: Add support for attached futexes Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-03 13:40 +0200
        Re: [RFC patch 4/7] futex: Add support for attached futexes Torvald Riegel <triegel@redhat.com> - 2016-04-05 09:50 +0200
        Re: [RFC patch 4/7] futex: Add support for attached futexes Carlos O'Donell <carlos@redhat.com> - 2016-04-05 18:00 +0200
  [RFC patch 7/7] [PATCH] glibc: nptl: Add support for attached  pthread_mutexes Thomas Gleixner <tglx@linutronix.de> - 2016-04-02 13:20 +0200
    Re: [RFC patch 7/7] [PATCH] glibc: nptl: Add support for attached  pthread_mutexes Peter Zijlstra <peterz@infradead.org> - 2016-04-02 18:40 +0200
      Re: [RFC patch 7/7] [PATCH] glibc: nptl: Add support for attached  pthread_mutexes Peter Zijlstra <peterz@infradead.org> - 2016-04-02 18:40 +0200
      Re: [RFC patch 7/7] [PATCH] glibc: nptl: Add support for attached  pthread_mutexes Thomas Gleixner <tglx@linutronix.de> - 2016-04-03 12:20 +0200

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