Documentation/locking/locktypes: Further clarifications and wordsmithing

[Sebastian Siewior]

On 2020-03-25 13:27:49 [+0100], Thomas Gleixner wrote:
> The documentation of rw_semaphores is wrong as it claims that the non-owner
> reader release is not supported by RT. That's just history biased memory
> distortion.
> 
> Split the 'Owner semantics' section up and add separate sections for
> semaphore and rw_semaphore to reflect reality.
> 
> Aside of that the following updates are done:
> 
>  - Add pseudo code to document the spinlock state preserving mechanism on
>    PREEMPT_RT
> 
>  - Wordsmith the bitspinlock and lock nesting sections
> 
> Co-developed-by: Paul McKenney <paulmck at kernel.org>
> Signed-off-by: Paul McKenney <paulmck at kernel.org>
> Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Acked-by: Sebastian Andrzej Siewior <bigeasy at linutronix.de>

> --- a/Documentation/locking/locktypes.rst
> +++ b/Documentation/locking/locktypes.rst
…
> +rw_semaphore
> +============
> +
> +rw_semaphore is a multiple readers and single writer lock mechanism.
> +
> +On non-PREEMPT_RT kernels the implementation is fair, thus preventing
> +writer starvation.
> +
> +rw_semaphore complies by default with the strict owner semantics, but there
> +exist special-purpose interfaces that allow non-owner release for readers.
> +These work independent of the kernel configuration.

This reads funny, could be my English. "This works independent …" maybe?

Sebastian