espressif: Don't hold interrupts disabled a long time

.. just to prevent background tasks from running

Author: jepler

shared-module/audiomp3/MP3Decoder.c

@@ -226,7 +226,7 @@ void common_hal_audiomp3_mp3file_construct(audiomp3_mp3file_obj_t *self,
 }
 
 void common_hal_audiomp3_mp3file_set_file(audiomp3_mp3file_obj_t *self, pyb_file_obj_t *file) {
-    background_callback_begin_critical_section();
+    background_callback_prevent();
 
     self->file = file;
     f_lseek(&self->file->fp, 0);
@@ -244,7 +244,7 @@ void common_hal_audiomp3_mp3file_set_file(audiomp3_mp3file_obj_t *self, pyb_file
     memset(self->buffers[1], 0, MAX_BUFFER_LEN);
     MP3FrameInfo fi;
     bool result = mp3file_get_next_frame_info(self, &fi);
-    background_callback_end_critical_section();
+    background_callback_allow();
     if (!result) {
         mp_raise_msg(&mp_type_RuntimeError,
             MP_ERROR_TEXT("Failed to parse MP3 file"));
@@ -296,7 +296,7 @@ void audiomp3_mp3file_reset_buffer(audiomp3_mp3file_obj_t *self,
     }
     // We don't reset the buffer index in case we're looping and we have an odd number of buffer
     // loads
-    background_callback_begin_critical_section();
+    background_callback_prevent();
     f_lseek(&self->file->fp, 0);
     self->inbuf_offset = self->inbuf_length;
     self->eof = 0;
@@ -305,7 +305,7 @@ void audiomp3_mp3file_reset_buffer(audiomp3_mp3file_obj_t *self,
     mp3file_update_inbuf_half(self);
     mp3file_skip_id3v2(self);
     mp3file_find_sync_word(self);
-    background_callback_end_critical_section();
+    background_callback_allow();
 }
 
 audioio_get_buffer_result_t audiomp3_mp3file_get_buffer(audiomp3_mp3file_obj_t *self,

supervisor/background_callback.h

@@ -89,8 +89,8 @@ void background_callback_reset(void);
  * bracket the section of code where this is the case.  These calls nest, and
  * begins must be balanced with ends.
  */
-void background_callback_begin_critical_section(void);
-void background_callback_end_critical_section(void);
+void background_callback_prevent(void);
+void background_callback_allow(void);
 
 /*
  * Background callbacks may stop objects from being collected

supervisor/shared/background_callback.c

@@ -76,18 +76,19 @@ inline bool background_callback_pending(void) {
     return callback_head != NULL;
 }
 
-static bool in_background_callback;
+static int background_prevention_count;
+
 void PLACE_IN_ITCM(background_callback_run_all)() {
     port_background_task();
     if (!background_callback_pending()) {
         return;
     }
     CALLBACK_CRITICAL_BEGIN;
-    if (in_background_callback) {
+    if (background_prevention_count) {
         CALLBACK_CRITICAL_END;
         return;
     }
-    in_background_callback = true;
+    ++background_prevention_count;
     background_callback_t *cb = (background_callback_t *)callback_head;
     callback_head = NULL;
     callback_tail = NULL;
@@ -104,15 +105,19 @@ void PLACE_IN_ITCM(background_callback_run_all)() {
         CALLBACK_CRITICAL_BEGIN;
         cb = next;
     }
-    in_background_callback = false;
+    --background_prevention_count;
     CALLBACK_CRITICAL_END;
 }
 
-void background_callback_begin_critical_section() {
+void background_callback_prevent() {
     CALLBACK_CRITICAL_BEGIN;
+    ++background_prevention_count;
+    CALLBACK_CRITICAL_END;
 }
 
-void background_callback_end_critical_section() {
+void background_callback_allow() {
+    CALLBACK_CRITICAL_BEGIN;
+    --background_prevention_count;
     CALLBACK_CRITICAL_END;
 }
 
@@ -146,7 +151,7 @@ void background_callback_reset() {
     }
     callback_head = new_head;
     callback_tail = new_tail;
-    in_background_callback = false;
+    background_prevention_count = 0;
     CALLBACK_CRITICAL_END;
 }