blob: e0a443e27109b47e823009a4d03f96ae076e367d (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
|
/**
* \file
* \brief RoundRobinQuantum class header
*
* \author Copyright (C) 2014-2016 Kamil Szczygiel http://www.distortec.com http://www.freddiechopin.info
*
* \par License
* This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not
* distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
#ifndef INCLUDE_DISTORTOS_INTERNAL_SCHEDULER_ROUNDROBINQUANTUM_HPP_
#define INCLUDE_DISTORTOS_INTERNAL_SCHEDULER_ROUNDROBINQUANTUM_HPP_
#include "distortos/TickClock.hpp"
namespace distortos
{
namespace internal
{
/// RoundRobinQuantum class is a quantum of time for round-robin scheduling
class RoundRobinQuantum
{
public:
/// type of quantum counter
using Representation = uint8_t;
/// duration type used for quantum
using Duration = std::chrono::duration<Representation, TickClock::period>;
/**
* \return initial value for round-robin quantum
*/
constexpr static Duration getInitial()
{
return Duration{quantumRawInitializer_};
}
/**
* \brief RoundRobinQuantum's constructor
*
* Initializes quantum value to initial value - just like after call to reset().
*/
constexpr RoundRobinQuantum() :
quantum_{getInitial()}
{
}
/**
* \brief Decrements round-robin's quantum.
*
* This function should be called from tick interrupt for the currently running thread. Underflow of quantum after
* this decrement is not possible.
*
* \note this function must be called with enabled interrupt masking
*/
void decrement()
{
if (isZero() == false)
--quantum_;
}
/**
* \brief Gets current value of round-robin's quantum.
*
* \return current value of round-robin's quantum of the thread
*/
Duration get() const
{
return quantum_;
}
/**
* \brief Convenience function to test whether the quantum is already at 0.
*
* \return true if quantum is zero, false otherwise
*/
bool isZero() const
{
return quantum_ == Duration{0};
}
/**
* \brief Resets value of round-robin's quantum.
*
* This function should be called from context switcher after selecting new task that will be run.
*/
void reset()
{
quantum_ = getInitial();
}
private:
static_assert(CONFIG_TICK_FREQUENCY > 0, "CONFIG_TICK_FREQUENCY must be positive and non-zero!");
static_assert(CONFIG_ROUND_ROBIN_FREQUENCY > 0, "CONFIG_ROUND_ROBIN_FREQUENCY must be positive and non-zero!");
/// raw initializer value for round-robin quantum, calculated with rounding to nearest
constexpr static auto quantumRawInitializer_ = (CONFIG_TICK_FREQUENCY + CONFIG_ROUND_ROBIN_FREQUENCY / 2) /
CONFIG_ROUND_ROBIN_FREQUENCY;
static_assert(quantumRawInitializer_ > 0 || quantumRawInitializer_ <= UINT8_MAX,
"CONFIG_TICK_FREQUENCY and CONFIG_ROUND_ROBIN_FREQUENCY values produce invalid round-robin quantum!");
/// round-robin quantum
Duration quantum_;
};
} // namespace internal
} // namespace distortos
#endif // INCLUDE_DISTORTOS_INTERNAL_SCHEDULER_ROUNDROBINQUANTUM_HPP_
|
