Re: [ECOS] nested interrupts

[Jonathan Larmour <jlarmour@redhat.com>]

Xavier Wang wrote:
[snip] 
> Which step above does indeed make the kernel state safe to be called by DSRs?
> 
> For example, an interrupt occurred while a thread is running in scheduler's critical
> section. It's not safe to manipulate scheduler's data in ISR obviously, but it seems
> also not safe to access scheduler's data in DSR since the interrupted thread still
> doesn't finish its job to make the data consistent. Am I wrong here?

DSRs are not called if the scheduler was already locked *before* the
interrupt. So the running thread just gets restored in the return from the
interrupt. It is the process of unlocking the scheduler, and specifically
the scheduler lock transitioning from the 1 to 0 state that causes DSRs to
run.

The sequence of events you cited is a simplification. For detail at this
level (after all, why do you need to know how - just know it is safe), Use
The Source Luke. DSRs are called from Cyg_Scheduler::unlock_inner() in
kernel/VERSION/src/sched/sched.cxx.

Jifl
-- 
Red Hat, Rustat House, Clifton Road, Cambridge, UK. Tel: +44 (1223) 271062
Un cheval, pas du glue. Pas du cheval, beaucoup du glue. || Opinions==mine