Marc Hoffman wrote: > 2. hardware dispatches to ex_trap_c unless otherwise handled > 3. ex_trap_c, modifies the LVL5 hardware event handler so no > hardware events can occur until the exception finishes (correct)? > then the exception is deferred to LVL5.
Actually it's only modified so that we can transfer control from an exception context to an interrupt context. It's restored immediately in _exception_to_level5. We can't really run kernel code in an exception context, so we chose IRQ5 as it's the highest-priority interrupt and can't be interrupted other than by another exception. This only happens for actual exceptions though: for things like syscalls, we transfer to a low-priority IRQ15 context which can be interrupted. CPLB faults must be handled in an exception context since they can arise from kernel code running in an IRQ5 context. The handler code for this must be written with special care so as to not cause additional exceptions. Bernd -- This footer brought to you by insane German lawmakers. Analog Devices GmbH Wilhelm-Wagenfeld-Str. 6 80807 Muenchen Registergericht Muenchen HRB 40368 Geschaeftsfuehrer Thomas Wessel, Vincent Roche, Joseph E. McDonough _______________________________________________ Uclinux-dist-devel mailing list Uclinux-dist-devel@blackfin.uclinux.org http://blackfin.uclinux.org/mailman/listinfo/uclinux-dist-devel
