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supervisor: Add a linked list of background callbacks
In time, we should transition interrupt driven background tasks out of the overall run_background_tasks into distinct background callbacks, so that the number of checks that occur with each tick is reduced.
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5 files changed

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5 files changed

+192
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lines changed

‎main.c

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@@ -45,6 +45,7 @@
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#include "background.h"
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#include "mpconfigboard.h"
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#include "supervisor/background_callback.h"
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#include "supervisor/cpu.h"
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#include "supervisor/memory.h"
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#include "supervisor/port.h"
@@ -161,6 +162,8 @@ void stop_mp(void) {
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MP_STATE_VM(vfs_cur) = vfs;
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#endif
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background_callback_reset();
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gc_deinit();
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}
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‎supervisor/background_callback.h

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/*
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* This file is part of the MicroPython project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2020 Jeff Epler for Adafruit Industries
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#ifndef CIRCUITPY_INCLUDED_SUPERVISOR_BACKGROUND_CALLBACK_H
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#define CIRCUITPY_INCLUDED_SUPERVISOR_BACKGROUND_CALLBACK_H
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/** Background callbacks are a linked list of tasks to call in the background.
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*
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* Include a member of type `background_callback_t` inside an object
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* which needs to queue up background work, and zero-initialize it.
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*
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* To schedule the work, use background_callback_add, with fun as the
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* function to call and data pointing to the object itself.
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*
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* Next time run_background_tasks_if_tick is called, the callback will
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* be run and removed from the linked list.
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*
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* Queueing a task that is already queued does nothing. Unconditionally
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* re-queueing it from its own background task will cause it to run during the
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* very next background-tasks invocation, leading to a CircuitPython freeze, so
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* don't do that.
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*
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* background_callback_add can be called from interrupt context.
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*/
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typedef void (*background_callback_fun)(void *data);
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typedef struct background_callback {
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background_callback_fun fun;
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void *data;
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struct background_callback *next;
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struct background_callback *prev;
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} background_callback_t;
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/* Add a background callback for which 'fun' and 'data' were previously set */
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void background_callback_add_core(background_callback_t *cb);
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/* Add a background callback to the given function with the given data. When
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* the callback involves an object on the GC heap, the 'data' must be a pointer
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* to that object itself, not an internal pointer. Otherwise, it can be the
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* case that no other references to the object itself survive, and the object
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* becomes garbage collected while an outstanding background callback still
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* exists.
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*/
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void background_callback_add(background_callback_t *cb, background_callback_fun fun, void *data);
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/* Run all background callbacks. Normally, this is done by the supervisor
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* whenever the list is non-empty */
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void background_callback_run_all(void);
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/* During soft reset, remove all pending callbacks and clear the critical section flag */
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void background_callback_reset(void);
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/* Sometimes background callbacks must be blocked. Use these functions to
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* bracket the section of code where this is the case. These calls nest, and
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* begins must be balanced with ends.
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*/
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void background_callback_begin_critical_section(void);
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void background_callback_end_critical_section(void);
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#endif

‎supervisor/shared/background_callback.c

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/*
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* This file is part of the MicroPython project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2020 Jeff Epler for Adafruit Industries
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "py/mpconfig.h"
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#include "supervisor/background_callback.h"
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#include "supervisor/shared/tick.h"
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#include "shared-bindings/microcontroller/__init__.h"
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STATIC volatile background_callback_t *callback_head, *callback_tail;
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#define CALLBACK_CRITICAL_BEGIN (common_hal_mcu_disable_interrupts())
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#define CALLBACK_CRITICAL_END (common_hal_mcu_enable_interrupts())
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void background_callback_add_core(background_callback_t *cb) {
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CALLBACK_CRITICAL_BEGIN;
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if (cb->prev || callback_head == cb) {
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CALLBACK_CRITICAL_END;
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return;
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}
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cb->next = 0;
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cb->prev = (background_callback_t*)callback_tail;
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if (callback_tail) {
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callback_tail->next = cb;
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cb->prev = (background_callback_t*)callback_tail;
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}
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if (!callback_head) {
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callback_head = cb;
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}
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callback_tail = cb;
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CALLBACK_CRITICAL_END;
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}
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void background_callback_add(background_callback_t *cb, background_callback_fun fun, void *data) {
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cb->fun = fun;
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cb->data = data;
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background_callback_add_core(cb);
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}
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static bool in_background_callback;
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void background_callback_run_all() {
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CALLBACK_CRITICAL_BEGIN;
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if(in_background_callback) {
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CALLBACK_CRITICAL_END;
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return;
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}
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in_background_callback = true;
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background_callback_t *cb = (background_callback_t*)callback_head;
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callback_head = NULL;
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callback_tail = NULL;
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while (cb) {
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background_callback_t *next = cb->next;
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cb->next = cb->prev = NULL;
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background_callback_fun fun = cb->fun;
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void *data = cb->data;
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CALLBACK_CRITICAL_END;
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// Leave the critical section in order to run the callback function
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if (fun) {
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fun(data);
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}
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CALLBACK_CRITICAL_BEGIN;
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cb = next;
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}
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in_background_callback = false;
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CALLBACK_CRITICAL_END;
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}
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void background_callback_begin_critical_section() {
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CALLBACK_CRITICAL_BEGIN;
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}
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void background_callback_end_critical_section() {
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CALLBACK_CRITICAL_END;
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}
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void background_callback_reset() {
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CALLBACK_CRITICAL_BEGIN;
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callback_head = NULL;
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callback_tail = NULL;
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in_background_callback = false;
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CALLBACK_CRITICAL_END;
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}

‎supervisor/shared/tick.c

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#include "py/mpstate.h"
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#include "supervisor/linker.h"
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#include "supervisor/filesystem.h"
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#include "supervisor/background_callback.h"
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#include "supervisor/port.h"
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#include "supervisor/shared/autoreload.h"
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@@ -86,10 +87,7 @@ uint32_t supervisor_ticks_ms32() {
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extern void run_background_tasks(void);
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void PLACE_IN_ITCM(supervisor_run_background_tasks_if_tick)() {
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// TODO: Add a global that can be set by anyone to indicate we should run background tasks. That
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// way we can short circuit the background tasks early. We used to do it based on time but it
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// breaks cases where we wake up for a short period and then sleep. If we skipped the last
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// background task or more before sleeping we may end up starving a task like USB.
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background_callback_run_all();
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run_background_tasks();
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}
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‎supervisor/supervisor.mk

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@@ -2,6 +2,7 @@ SRC_SUPERVISOR = \
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main.c \
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supervisor/port.c \
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supervisor/shared/autoreload.c \
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supervisor/shared/background_callback.c \
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supervisor/shared/board.c \
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supervisor/shared/filesystem.c \
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supervisor/shared/flash.c \

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