C11 Re: [PATCH 3/6] termios: Use C11 mutex for input/output

[Sebastian Huber]

On 19/12/16 22:31, Chris Johns wrote:
> On 19/12/2016 17:32, Sebastian Huber wrote:
>> On 16/12/16 21:50, Chris Johns wrote:
>>> If the same storage model and performance can be gained with POSIX why
>>> not look at moving in this direction.
>>
>> We should change the POSIX synchronization objects
>>
>> * mutexes,
>> * rwlocks,
>> * barriers,
>> * condition variables,
>> * keys, and
>> * semaphores
>>
>> into self-contained objects from my point of view.
>
> Why has threads been left off?

Providing self-contained threads would be considerable more work. You 
have to deal with the stack and thread-local storage with a link-time 
defined size.

>
>> Since the POSIX types
>> are now defined in a system-specific header file, this is quite easy:
>>
>> https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;a=blob;f=newlib/libc/sys/rtems/include/sys/_pthreadtypes.h;h=bd66c689ecf0a3ef335867b5a08d32f9dfe9041b;hb=HEAD 
>>
>>
>> Its about a man week of work to do this.
>>
>
> OK.
>
>> The performance will be not optimal, since we have to check if we
>> actually have a non-recursive, recursive, ceiling or robust mutex.
>
> What is optimal performance?

In case of mutexes the implementation that yields the most 
acquire/release operations per second for an uncontested mutex.

-- 
Sebastian Huber, embedded brains GmbH

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