[ECOS] unlock_inner and DSR scheduling

["Corrin Meyer" <cjmeyer at gmail dot com>]

I am new to eCos and so still figuring out how it works.

The function unlock_inner is acting as the main mechanism by which
context switches occur.  An inline wrapper function
Cyg_Scheduler::reschedule, as per the comment, is suppose to
essentially by a unlock()/lock() sequence whithout actually
decrementing the lock count.

1. This seems a bit inaccurate as a unlock()/lock() sequence would not
result in thread rescheduling if the lock count was greater than 1
whereas reschedule() seems to allow the possibility of rescheduling.
Is the comment right and I am missing something or is my
interpretation correct?

2. Inside the Cyg_Scheduler::unlock_inner, DSRs are not run unless the
new lock value is 0 (lock going to 0).  While this makes sense in
general, unlock_inner() never seems to be called unless threads are
permitted to be rescheduled so if threads are being rescheduled
wouldn't it make sense to have DSRs always run prior to rescheduling
in order to minimize the number of context switches (since after the
context switch, if the thread switched to restores the lock to 0 the
and pending DSRs will be run again and could result in another thread
rescheduling).

cjmeyer

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