1 /*
2 * Copyright (c) 2016, The OpenThread Authors.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * 3. Neither the name of the copyright holder nor the
13 * names of its contributors may be used to endorse or promote products
14 * derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
17 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
20 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 /**
30 * @file
31 * This file implements the tasklet scheduler.
32 */
33
34 #include "tasklet.hpp"
35
36 #include "common/code_utils.hpp"
37 #include "instance/instance.hpp"
38
39 namespace ot {
40
Post(void)41 void Tasklet::Post(void)
42 {
43 if (!IsPosted())
44 {
45 Get<Scheduler>().PostTasklet(*this);
46 }
47 }
48
Unpost(void)49 void Tasklet::Unpost(void)
50 {
51 if (IsPosted())
52 {
53 Get<Scheduler>().RemoveTasklet(*this);
54 }
55 }
56
PostTasklet(Tasklet & aTasklet)57 void Tasklet::Scheduler::PostTasklet(Tasklet &aTasklet)
58 {
59 // Tasklets are saved in a circular singly linked list.
60
61 if (mTail == nullptr)
62 {
63 mTail = &aTasklet;
64 mTail->mNext = mTail;
65 otTaskletsSignalPending(&aTasklet.GetInstance());
66 }
67 else
68 {
69 aTasklet.mNext = mTail->mNext;
70 mTail->mNext = &aTasklet;
71 mTail = &aTasklet;
72 }
73 }
74
RemoveTasklet(Tasklet & aTasklet)75 void Tasklet::Scheduler::RemoveTasklet(Tasklet &aTasklet)
76 {
77 Tasklet *prev = mTail;
78
79 while (prev->mNext != &aTasklet)
80 {
81 prev = prev->mNext;
82 }
83
84 prev->mNext = aTasklet.mNext;
85 aTasklet.mNext = nullptr;
86
87 if (mTail == &aTasklet)
88 {
89 mTail = (prev != &aTasklet) ? prev : nullptr;
90 }
91 }
92
ProcessQueuedTasklets(void)93 void Tasklet::Scheduler::ProcessQueuedTasklets(void)
94 {
95 Tasklet *tail = mTail;
96
97 // This method processes all tasklets queued when this is called. We
98 // keep a copy the current list and then clear the main list by
99 // setting `mTail` to `nullptr`. A newly posted tasklet while
100 // processing the currently queued tasklets will then trigger a call
101 // to `otTaskletsSignalPending()`.
102
103 mTail = nullptr;
104
105 while (tail != nullptr)
106 {
107 Tasklet *tasklet = tail->mNext;
108
109 if (tasklet == tail)
110 {
111 tail = nullptr;
112 }
113 else
114 {
115 tail->mNext = tasklet->mNext;
116 }
117
118 tasklet->mNext = nullptr;
119 tasklet->RunTask();
120 }
121 }
122
123 } // namespace ot
124