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de88b08b94
This is about doing the best with what we have. As delayed tasks can't be cancelled, and dcSCTP timers will almost always be stopped or restarted, and will generally only expire on packet loss. This implementation will post a delayed task whenever a Timeout is started. Whenever it's stopped or restarted, it will keep the scheduled delay task running (there's no alternative), but it will also not start a new delayed task on subsequent starts/restarts. Instead, it will wait until the original delayed task has triggered, and will then - if the timer is still running, which it probably isn't - post a new delayed task with the remainder of the the duration. There is special handling for when a shorter duration is requested, as that can't re-use the scheduled task, but that shouldn't be very common. Bug: webrtc:12614 Change-Id: I7f3269cabf84f80dae3b8a528243414a93d50fc4 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/217223 Reviewed-by: Tommi <tommi@webrtc.org> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Commit-Queue: Victor Boivie <boivie@webrtc.org> Cr-Commit-Position: refs/heads/master@{#33904}
96 lines
4.1 KiB
C++
96 lines
4.1 KiB
C++
/*
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* Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "net/dcsctp/timer/task_queue_timeout.h"
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#include "rtc_base/logging.h"
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#include "rtc_base/task_utils/pending_task_safety_flag.h"
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#include "rtc_base/task_utils/to_queued_task.h"
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namespace dcsctp {
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TaskQueueTimeoutFactory::TaskQueueTimeout::TaskQueueTimeout(
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TaskQueueTimeoutFactory& parent)
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: parent_(parent),
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pending_task_safety_flag_(webrtc::PendingTaskSafetyFlag::Create()) {}
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TaskQueueTimeoutFactory::TaskQueueTimeout::~TaskQueueTimeout() {
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RTC_DCHECK_RUN_ON(&parent_.thread_checker_);
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pending_task_safety_flag_->SetNotAlive();
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}
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void TaskQueueTimeoutFactory::TaskQueueTimeout::Start(DurationMs duration_ms,
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TimeoutID timeout_id) {
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RTC_DCHECK_RUN_ON(&parent_.thread_checker_);
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RTC_DCHECK(timeout_expiration_ == TimeMs::InfiniteFuture());
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timeout_expiration_ = parent_.get_time_() + duration_ms;
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timeout_id_ = timeout_id;
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if (timeout_expiration_ >= posted_task_expiration_) {
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// There is already a running task, and it's scheduled to expire sooner than
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// the new expiration time. Don't do anything; The `timeout_expiration_` has
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// already been updated and if the delayed task _does_ expire and the timer
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// hasn't been stopped, that will be noticed in the timeout handler, and the
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// task will be re-scheduled. Most timers are stopped before they expire.
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return;
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}
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if (posted_task_expiration_ != TimeMs::InfiniteFuture()) {
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RTC_DLOG(LS_VERBOSE) << "New timeout duration is less than scheduled - "
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"ghosting old delayed task.";
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// There is already a scheduled delayed task, but its expiration time is
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// further away than the new expiration, so it can't be used. It will be
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// "killed" by replacing the safety flag. This is not expected to happen
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// especially often; Mainly when a timer did exponential backoff and
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// later recovered.
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pending_task_safety_flag_->SetNotAlive();
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pending_task_safety_flag_ = webrtc::PendingTaskSafetyFlag::Create();
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}
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posted_task_expiration_ = timeout_expiration_;
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parent_.task_queue_.PostDelayedTask(
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webrtc::ToQueuedTask(
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pending_task_safety_flag_,
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[timeout_id, this]() {
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RTC_DLOG(LS_VERBOSE) << "Timout expired: " << timeout_id.value();
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RTC_DCHECK_RUN_ON(&parent_.thread_checker_);
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RTC_DCHECK(posted_task_expiration_ != TimeMs::InfiniteFuture());
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posted_task_expiration_ = TimeMs::InfiniteFuture();
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if (timeout_expiration_ == TimeMs::InfiniteFuture()) {
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// The timeout was stopped before it expired. Very common.
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} else {
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// Note that the timeout might have been restarted, which updated
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// `timeout_expiration_` but left the scheduled task running. So
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// if it's not quite time to trigger the timeout yet, schedule a
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// new delayed task with what's remaining and retry at that point
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// in time.
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DurationMs remaining = timeout_expiration_ - parent_.get_time_();
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timeout_expiration_ = TimeMs::InfiniteFuture();
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if (*remaining > 0) {
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Start(remaining, timeout_id_);
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} else {
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// It has actually triggered.
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RTC_DLOG(LS_VERBOSE)
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<< "Timout triggered: " << timeout_id.value();
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parent_.on_expired_(timeout_id_);
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}
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}
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}),
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duration_ms.value());
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}
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void TaskQueueTimeoutFactory::TaskQueueTimeout::Stop() {
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// As the TaskQueue doesn't support deleting a posted task, just mark the
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// timeout as not running.
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RTC_DCHECK_RUN_ON(&parent_.thread_checker_);
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timeout_expiration_ = TimeMs::InfiniteFuture();
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}
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} // namespace dcsctp
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