cc3200: Fix thread mutex's so threading works with interrupts.

dpgeorge · dpgeorge · commit 17ba6ef5fa75 · 2016-10-19T14:24:56.000+11:00
Running Python code on a hard interrupt is incompatible with having a GIL, because most of the time the GIL will be held by the user thread when the interrupt arrives. Hard interrupts mean that we should process them right away and hence can't wait until the GIL is released. The problem with the current code is that a hard interrupt will try to exit/enter the GIL while it is still held by the user thread, hence leading to a deadlock. This patch works around such a problem by just making GIL exit/enter a no-op when in an interrupt context, or when interrupts are disabled. See issue adafruit#2406.
diff --git a/cc3200/mpthreadport.c b/cc3200/mpthreadport.c
@@ -31,8 +31,10 @@
 #include "py/runtime.h"
 #include "py/gc.h"
 #include "py/mpthread.h"
+#include "py/mphal.h"
 #include "mptask.h"
 #include "task.h"
+#include "irq.h"
 
 #if MICROPY_PY_THREAD
 
@@ -166,14 +168,23 @@ void mp_thread_mutex_init(mp_thread_mutex_t *mutex) {
     mutex->handle = xSemaphoreCreateMutexStatic(&mutex->buffer);
 }
 
+// To allow hard interrupts to work with threading we only take/give the semaphore
+// if we are not within an interrupt context and interrupts are enabled.
+
 int mp_thread_mutex_lock(mp_thread_mutex_t *mutex, int wait) {
-    int ret = xSemaphoreTake(mutex->handle, wait ? portMAX_DELAY : 0);
-    return ret == pdTRUE;
+    if ((HAL_NVIC_INT_CTRL_REG & HAL_VECTACTIVE_MASK) == 0 && query_irq() == IRQ_STATE_ENABLED) {
+        int ret = xSemaphoreTake(mutex->handle, wait ? portMAX_DELAY : 0);
+        return ret == pdTRUE;
+    } else {
+        return 1;
+    }
 }
 
 void mp_thread_mutex_unlock(mp_thread_mutex_t *mutex) {
-    xSemaphoreGive(mutex->handle);
-    // TODO check return value
+    if ((HAL_NVIC_INT_CTRL_REG & HAL_VECTACTIVE_MASK) == 0 && query_irq() == IRQ_STATE_ENABLED) {
+        xSemaphoreGive(mutex->handle);
+        // TODO check return value
+    }
 }
 
 #endif // MICROPY_PY_THREAD
