Re: [ANNOUNCE] Linux 2.6 Real Time Kernel

[Eugeny S. Mints]

Vadim Lebedev wrote:
> Sven-Thorsten Dietrich <sdietrich@xxxxxxxxxx> wrote in message 
> news:<2Nir3-4iC-13@xxxxxxxxxxxxxxxx>...
>
> > Announcing the availability of prototype real-time (RT)
> > enhancements to the Linux 2.6 kernel.
>
>
> Reading the sources i believe that __p_mutex_up  is not constant time
> operation because of __p_mutex_down....
>
> It is clear that
> __p_mutex_down is not constant time operation because of insertion
> into the priority-sorted sleepers list.  However both __p_mutex_down
> and __p_mutex_up are synchronize on the same global spinlock
> (m_spin_lock) ....  so if the __p_mutex_down is holding this spinlock
> while inserting NO other process(or) is able to perform any __p_mutex
> operation...

Current pmutex implementation was chosen only as prototype 
implementation. kmutex abstraction layer allows to switch easily between 
any (alternative) mutex implementations and to choose optimal one on a 
benchmarking basis.

> Maybe the better idea would be to have a per-mutex spinlock? or even
> better, given that the task->rt_priority have a finite range maybe each
> mutex can have a table of sleeper lists indexed by rt_priority?
>
>
> Vadim
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