shared/runtime/mpirq: Check separate hard IRQ stack correctly.

On the zephyr port, hard IRQ handlers run with a separate stack on a
different thread, so each call to mp_irq_dispatch() and mp_irq_handler()
has to be wrapped with adjustments to the stack-limit checker.

Move these adjustments into the shared mp_irq_dispatch(), introducing
MICROPY_STACK_SIZE_HARD_IRQ which a port can define to non-zero if it
uses a separate stack for hard IRQ handlers. We only need wrap the hard
dispatch case. This should reduce binary size on zephyr without affecting
other ports.

Signed-off-by: Chris Webb <chris@arachsys.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/shared/runtime/mpirq.c b/shared/runtime/mpirq.c
index 0b3489c51..4d848ae7e 100644
--- a/shared/runtime/mpirq.c
+++ b/shared/runtime/mpirq.c
@@ -69,6 +69,15 @@ int mp_irq_dispatch(mp_obj_t handler, mp_obj_t parent, bool ishard) {
     int result = 0;
     if (handler != mp_const_none) {
         if (ishard) {
+            #if MICROPY_STACK_CHECK && MICROPY_STACK_SIZE_HARD_IRQ > 0
+            // This callback executes in an ISR context so the stack-limit
+            // check must be changed to use the ISR stack for the duration
+            // of this function.
+            char *orig_stack_top = MP_STATE_THREAD(stack_top);
+            size_t orig_stack_limit = MP_STATE_THREAD(stack_limit);
+            mp_cstack_init_with_sp_here(MICROPY_STACK_SIZE_HARD_IRQ);
+            #endif
+
             // When executing code within a handler we must lock the scheduler to
             // prevent any scheduled callbacks from running, and lock the GC to
             // prevent any memory allocations.
@@ -85,6 +94,12 @@ int mp_irq_dispatch(mp_obj_t handler, mp_obj_t parent, bool ishard) {
             }
             gc_unlock();
             mp_sched_unlock();
+
+            #if MICROPY_STACK_CHECK && MICROPY_STACK_SIZE_HARD_IRQ > 0
+            // Restore original stack-limit checking values.
+            MP_STATE_THREAD(stack_top) = orig_stack_top;
+            MP_STATE_THREAD(stack_limit) = orig_stack_limit;
+            #endif
         } else {
             // Schedule call to user function
             mp_sched_schedule(handler, parent);