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

[Andy Lutomirski]

On Sun, Apr 3, 2016 at 2:57 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> 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?

Why can't private futexes be attached by default?

--Andy