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// Copyright 2020 The Pigweed Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
#include "pw_thread/thread.h"
#include "FreeRTOS.h"
#include "pw_assert/check.h"
#include "pw_preprocessor/compiler.h"
#include "pw_thread/id.h"
#include "pw_thread_freertos/config.h"
#include "pw_thread_freertos/context.h"
#include "pw_thread_freertos/options.h"
#include "task.h"
using pw::thread::freertos::Context;
namespace pw::thread {
namespace {
#if PW_THREAD_JOINING_ENABLED
constexpr EventBits_t kThreadDoneBit = 1 << 0;
#endif // PW_THREAD_JOINING_ENABLED
} // namespace
void Context::ThreadEntryPoint(void* void_context_ptr) {
Context& context = *static_cast<Context*>(void_context_ptr);
// Invoke the user's thread function. This may never return.
context.user_thread_entry_function_(context.user_thread_entry_arg_);
// Use a task only critical section to guard against join() and detach().
vTaskSuspendAll();
if (context.detached()) {
// There is no threadsafe way to re-use detached threads, as there's no way
// to signal the vTaskDelete success. Joining MUST be used for this.
// However to enable unit test coverage we go ahead and clear this.
context.set_task_handle(nullptr);
#if PW_THREAD_JOINING_ENABLED
// If the thread handle was detached before the thread finished execution,
// i.e. got here, then we are responsible for cleaning up the join event
// group.
vEventGroupDelete(&context.join_event_group());
#endif // PW_THREAD_JOINING_ENABLED
#if PW_THREAD_FREERTOS_CONFIG_DYNAMIC_ALLOCATION_ENABLED
// The thread was detached before the task finished, free any allocations
// it ran on.
if (context.dynamically_allocated()) {
delete &context;
}
#endif // PW_THREAD_FREERTOS_CONFIG_DYNAMIC_ALLOCATION_ENABLED
// Re-enable the scheduler before we delete this execution.
xTaskResumeAll();
vTaskDelete(nullptr);
PW_UNREACHABLE;
}
// Otherwise the task finished before the thread was detached or joined, defer
// cleanup to Thread's join() or detach().
context.set_thread_done();
xTaskResumeAll();
#if PW_THREAD_JOINING_ENABLED
xEventGroupSetBits(&context.join_event_group(), kThreadDoneBit);
#endif // PW_THREAD_JOINING_ENABLED
while (true) {
#if INCLUDE_vTaskSuspend == 1
// Use indefinite suspension when available.
vTaskSuspend(nullptr);
#else
vTaskDelay(portMAX_DELAY);
#endif // INCLUDE_vTaskSuspend == 1
}
PW_UNREACHABLE;
}
void Context::TerminateThread(Context& context) {
// Stop the other task first.
PW_DCHECK_NOTNULL(context.task_handle(), "We shall not delete ourselves!");
vTaskDelete(context.task_handle());
// Mark the context as unused for potential later re-use.
context.set_task_handle(nullptr);
#if PW_THREAD_JOINING_ENABLED
// Just in case someone abused our API, ensure their use of the event group is
// properly handled by the kernel regardless.
vEventGroupDelete(&context.join_event_group());
#endif // PW_THREAD_JOINING_ENABLED
#if PW_THREAD_FREERTOS_CONFIG_DYNAMIC_ALLOCATION_ENABLED
// Then free any allocations it ran on.
if (context.dynamically_allocated()) {
delete &context;
}
#endif // PW_THREAD_FREERTOS_CONFIG_DYNAMIC_ALLOCATION_ENABLED
}
Thread::Thread(const thread::Options& facade_options,
ThreadRoutine entry,
void* arg)
: native_type_(nullptr) {
// Cast the generic facade options to the backend specific option of which
// only one type can exist at compile time.
auto options = static_cast<const freertos::Options&>(facade_options);
if (options.static_context() != nullptr) {
// Use the statically allocated context.
native_type_ = options.static_context();
// Can't use a context more than once.
PW_DCHECK_PTR_EQ(native_type_->task_handle(), nullptr);
// Reset the state of the static context in case it was re-used.
native_type_->set_detached(false);
native_type_->set_thread_done(false);
#if PW_THREAD_JOINING_ENABLED
const EventGroupHandle_t event_group_handle =
xEventGroupCreateStatic(&native_type_->join_event_group());
PW_DCHECK_PTR_EQ(event_group_handle,
&native_type_->join_event_group(),
"Failed to create the joining event group");
#endif // PW_THREAD_JOINING_ENABLED
// In order to support functions which return and joining, a delegate is
// deep copied into the context with a small wrapping function to actually
// invoke the task with its arg.
native_type_->set_thread_routine(entry, arg);
const TaskHandle_t task_handle =
xTaskCreateStatic(Context::ThreadEntryPoint,
options.name(),
options.static_context()->stack().size(),
native_type_,
options.priority(),
options.static_context()->stack().data(),
&options.static_context()->tcb());
PW_CHECK_NOTNULL(task_handle); // Ensure it succeeded.
native_type_->set_task_handle(task_handle);
} else {
#if !PW_THREAD_FREERTOS_CONFIG_DYNAMIC_ALLOCATION_ENABLED
PW_CRASH(
"dynamic thread allocations are not enabled and no static_context "
"was provided");
#else // PW_THREAD_FREERTOS_CONFIG_DYNAMIC_ALLOCATION_ENABLED
// Dynamically allocate the context and the task.
native_type_ = new pw::thread::freertos::Context();
native_type_->set_dynamically_allocated();
#if PW_THREAD_JOINING_ENABLED
const EventGroupHandle_t event_group_handle =
xEventGroupCreateStatic(&native_type_->join_event_group());
PW_DCHECK_PTR_EQ(event_group_handle,
&native_type_->join_event_group(),
"Failed to create the joining event group");
#endif // PW_THREAD_JOINING_ENABLED
// In order to support functions which return and joining, a delegate is
// deep copied into the context with a small wrapping function to actually
// invoke the task with its arg.
native_type_->set_thread_routine(entry, arg);
TaskHandle_t task_handle;
const BaseType_t result = xTaskCreate(Context::ThreadEntryPoint,
options.name(),
options.stack_size_words(),
native_type_,
options.priority(),
&task_handle);
// Ensure it succeeded.
PW_CHECK_UINT_EQ(result, pdPASS);
native_type_->set_task_handle(task_handle);
#endif // !PW_THREAD_FREERTOS_CONFIG_DYNAMIC_ALLOCATION_ENABLED
}
}
void Thread::detach() {
PW_CHECK(joinable());
#if INCLUDE_vTaskSuspend == 1
// No need to suspend extra tasks.
vTaskSuspend(native_type_->task_handle());
#else
vTaskSuspendAll();
#endif // INCLUDE_vTaskSuspend == 1
native_type_->set_detached();
const bool thread_done = native_type_->thread_done();
#if INCLUDE_vTaskSuspend == 1
// No need to suspend extra tasks.
vTaskResume(native_type_->task_handle());
#else
vTaskResumeAll();
#endif // INCLUDE_vTaskSuspend == 1
if (thread_done) {
// The task finished (hit end of Context::ThreadEntryPoint) before we
// invoked detach, clean up the thread.
Context::TerminateThread(*native_type_);
} else {
// We're detaching before the task finished, defer cleanup to the task at
// the end of Context::ThreadEntryPoint.
}
// Update to no longer represent a thread of execution.
native_type_ = nullptr;
}
#if PW_THREAD_JOINING_ENABLED
void Thread::join() {
PW_CHECK(joinable());
PW_CHECK(this_thread::get_id() != get_id());
// Wait indefinitely until kThreadDoneBit is set.
while (xEventGroupWaitBits(&native_type_->join_event_group(),
kThreadDoneBit,
pdTRUE, // Clear the bits.
pdFALSE, // Any bits is fine, N/A.
portMAX_DELAY) != kThreadDoneBit) {
}
// No need for a critical section here as the thread at this point is
// waiting to be terminated.
Context::TerminateThread(*native_type_);
// Update to no longer represent a thread of execution.
native_type_ = nullptr;
}
#endif // PW_THREAD_JOINING_ENABLED
} // namespace pw::thread