Re: [ECOS] About Cyg_Scheduler::unlock_inner

[Jonathan Larmour <jlarmour@redhat.com>]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 918 bytes --]

Rafael Rodríguez Velilla wrote:
> 
>   I'm working with eCos 1.3.1 and I have a question about
> Cyg_Scheduler::unlock_inner.
> 
>   This method is only called when  calling Cyg_Scheduler::unlock with
> sched_lock=1; (so it should become 0)
>   I have seen in the code that it first calls any pending DSR (if there
> is any) and then it checks if there's a new thread that reclaims the
> CPU.
>   Why is the context of the new thread restored before decrementing
> sched_lock?

You can't be in the process of switching the context when there's a chance
the system could be rescheduled again (e.g. due to a new interrupt).

>   Why is not the new thread run with the scheduler unlocked?

Once it is restored, it unlocks the scheduler almost straight away.

Jifl
-- 
Red Hat, Rustat House, Clifton Road, Cambridge, UK. Tel: +44 (1223) 271062
Maybe this world is another planet's Hell -Aldous Huxley || Opinions==mine