Re: [Xenomai-core] Fast userspace locks for native skin

[Jan Kiszka <jan.kiszka@domain.hid>]

Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
>> Gilles Chanteperdrix wrote:
>>> decision (we could store the first pending thread priority in a
>>> user/kernel shared area, with the complication that we would need
>>> updating this priority if it ever changes, but to get the priority of
>>> the current thread, we also need a syscall, moreover switching to
>>> secondary mode).
>> I'm not thinking about the case where there is already someone waiting.
>> That will need a kernel entry anyway (the low-prio waiter may sit on
>> some other CPU...). But in case signaling always happens before pending,
>> there is no need at all to consult the kernel.
> 
> In this case, you can avoid calling pthread_cond_signal at all... So, if
> you are stupid enough to call pthread_cond_signal when no-one is
> waiting, you deserve a syscall anyway.

Yes, algorithmically avoidable. OK, let's see if there is someone who
actually has a need for it (legacy code...).

Jan

-- 
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux