1 /*
2 * COPYRIGHT (C) 2018, Real-Thread Information Technology Ltd
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 *
6 * Change Logs:
7 * Date Author Notes
8 * 2014-04-16 Grissiom first version
9 */
10
11 struct rt_watermark_queue
12 {
13 /* Current water level. */
14 unsigned int level;
15 unsigned int high_mark;
16 unsigned int low_mark;
17 rt_list_t suspended_threads;
18 };
19
20 /** Init the struct rt_watermark_queue.
21 */
22 void rt_wm_que_init(struct rt_watermark_queue *wg,
23 unsigned int low, unsigned int high);
24 void rt_wm_que_set_mark(struct rt_watermark_queue *wg,
25 unsigned int low, unsigned int high);
26 void rt_wm_que_dump(struct rt_watermark_queue *wg);
27
28 /* Water marks are often used in performance critical places. Benchmark shows
29 * inlining functions will have 10% performance gain in some situation(for
30 * example, VBus). So keep the inc/dec compact and inline. */
31
32 /** Increase the water level.
33 *
34 * It should be called in the thread that want to raise the water level. If the
35 * current level is above the high mark, the thread will be suspended up to
36 * @timeout ticks.
37 *
38 * @return RT_EOK if water level increased successfully. -RT_EFULL on @timeout
39 * is zero and the level is above water mark. -RT_ETIMEOUT if timeout occurred.
40 */
rt_wm_que_inc(struct rt_watermark_queue * wg,int timeout)41 rt_inline rt_err_t rt_wm_que_inc(struct rt_watermark_queue *wg,
42 int timeout)
43 {
44 rt_base_t ilvl;
45
46 /* Assert as early as possible. */
47 if (timeout != 0)
48 {
49 RT_DEBUG_IN_THREAD_CONTEXT;
50 }
51
52 ilvl = rt_hw_interrupt_disable();
53
54 while (wg->level > wg->high_mark)
55 {
56 rt_thread_t thread;
57
58 if (timeout == 0)
59 {
60 rt_hw_interrupt_enable(ilvl);
61 return -RT_EFULL;
62 }
63
64 thread = rt_thread_self();
65 thread->error = RT_EOK;
66 rt_thread_suspend(thread);
67 rt_list_insert_after(&wg->suspended_threads, &thread->tlist);
68 if (timeout > 0)
69 {
70 rt_timer_control(&(thread->thread_timer),
71 RT_TIMER_CTRL_SET_TIME,
72 &timeout);
73 rt_timer_start(&(thread->thread_timer));
74 }
75 rt_hw_interrupt_enable(ilvl);
76 rt_schedule();
77 if (thread->error != RT_EOK)
78 return thread->error;
79
80 ilvl = rt_hw_interrupt_disable();
81 }
82
83 wg->level++;
84
85 if (wg->level == 0)
86 {
87 wg->level = ~0;
88 }
89
90 rt_hw_interrupt_enable(ilvl);
91
92 return RT_EOK;
93 }
94
95 /** Decrease the water level.
96 *
97 * It should be called by the consumer that drain the water out. If the water
98 * level reached low mark, all the thread suspended in this queue will be waken
99 * up. It's safe to call this function in interrupt context.
100 */
rt_wm_que_dec(struct rt_watermark_queue * wg)101 rt_inline void rt_wm_que_dec(struct rt_watermark_queue *wg)
102 {
103 int need_sched = 0;
104 rt_base_t ilvl;
105
106 if (wg->level == 0)
107 return;
108
109 ilvl = rt_hw_interrupt_disable();
110 wg->level--;
111 if (wg->level == wg->low_mark)
112 {
113 /* There should be spaces between the low mark and high mark, so it's
114 * safe to resume all the threads. */
115 while (!rt_list_isempty(&wg->suspended_threads))
116 {
117 rt_thread_t thread;
118
119 thread = rt_list_entry(wg->suspended_threads.next,
120 struct rt_thread,
121 tlist);
122 rt_thread_resume(thread);
123 need_sched = 1;
124 }
125 }
126 rt_hw_interrupt_enable(ilvl);
127
128 if (need_sched)
129 rt_schedule();
130 }
131