Commit | Line | Data |
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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
34f971f6 PZ |
2 | /* |
3 | * stop-task scheduling class. | |
4 | * | |
5 | * The stop task is the highest priority task in the system, it preempts | |
6 | * everything and will be preempted by nothing. | |
7 | * | |
8 | * See kernel/stop_machine.c | |
9 | */ | |
97fb7a0a | 10 | #include "sched.h" |
34f971f6 PZ |
11 | |
12 | #ifdef CONFIG_SMP | |
13 | static int | |
3aef1551 | 14 | select_task_rq_stop(struct task_struct *p, int cpu, int flags) |
34f971f6 PZ |
15 | { |
16 | return task_cpu(p); /* stop tasks as never migrate */ | |
17 | } | |
6e2df058 PZ |
18 | |
19 | static int | |
20 | balance_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) | |
21 | { | |
22 | return sched_stop_runnable(rq); | |
23 | } | |
34f971f6 PZ |
24 | #endif /* CONFIG_SMP */ |
25 | ||
26 | static void | |
27 | check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags) | |
28 | { | |
1e5a7405 | 29 | /* we're never preempted */ |
34f971f6 PZ |
30 | } |
31 | ||
a0e813f2 | 32 | static void set_next_task_stop(struct rq *rq, struct task_struct *stop, bool first) |
03b7fad1 PZ |
33 | { |
34 | stop->se.exec_start = rq_clock_task(rq); | |
35 | } | |
36 | ||
21f56ffe | 37 | static struct task_struct *pick_task_stop(struct rq *rq) |
34f971f6 | 38 | { |
6e2df058 | 39 | if (!sched_stop_runnable(rq)) |
606dba2e | 40 | return NULL; |
34f971f6 | 41 | |
6e2df058 | 42 | return rq->stop; |
34f971f6 PZ |
43 | } |
44 | ||
21f56ffe PZ |
45 | static struct task_struct *pick_next_task_stop(struct rq *rq) |
46 | { | |
47 | struct task_struct *p = pick_task_stop(rq); | |
48 | ||
49 | if (p) | |
50 | set_next_task_stop(rq, p, true); | |
51 | ||
52 | return p; | |
53 | } | |
54 | ||
34f971f6 PZ |
55 | static void |
56 | enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags) | |
57 | { | |
72465447 | 58 | add_nr_running(rq, 1); |
34f971f6 PZ |
59 | } |
60 | ||
61 | static void | |
62 | dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags) | |
63 | { | |
72465447 | 64 | sub_nr_running(rq, 1); |
34f971f6 PZ |
65 | } |
66 | ||
67 | static void yield_task_stop(struct rq *rq) | |
68 | { | |
69 | BUG(); /* the stop task should never yield, its pointless. */ | |
70 | } | |
71 | ||
6e2df058 | 72 | static void put_prev_task_stop(struct rq *rq, struct task_struct *prev) |
34f971f6 | 73 | { |
8f618968 MG |
74 | struct task_struct *curr = rq->curr; |
75 | u64 delta_exec; | |
76 | ||
78becc27 | 77 | delta_exec = rq_clock_task(rq) - curr->se.exec_start; |
8f618968 MG |
78 | if (unlikely((s64)delta_exec < 0)) |
79 | delta_exec = 0; | |
80 | ||
ceeadb83 YS |
81 | schedstat_set(curr->stats.exec_max, |
82 | max(curr->stats.exec_max, delta_exec)); | |
8f618968 MG |
83 | |
84 | curr->se.sum_exec_runtime += delta_exec; | |
85 | account_group_exec_runtime(curr, delta_exec); | |
86 | ||
78becc27 | 87 | curr->se.exec_start = rq_clock_task(rq); |
d2cc5ed6 | 88 | cgroup_account_cputime(curr, delta_exec); |
34f971f6 PZ |
89 | } |
90 | ||
d84b3131 FW |
91 | /* |
92 | * scheduler tick hitting a task of our scheduling class. | |
93 | * | |
94 | * NOTE: This function can be called remotely by the tick offload that | |
95 | * goes along full dynticks. Therefore no local assumption can be made | |
96 | * and everything must be accessed through the @rq and @curr passed in | |
97 | * parameters. | |
98 | */ | |
34f971f6 PZ |
99 | static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued) |
100 | { | |
101 | } | |
102 | ||
da7a735e | 103 | static void switched_to_stop(struct rq *rq, struct task_struct *p) |
34f971f6 PZ |
104 | { |
105 | BUG(); /* its impossible to change to this class */ | |
106 | } | |
107 | ||
da7a735e PZ |
108 | static void |
109 | prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio) | |
34f971f6 PZ |
110 | { |
111 | BUG(); /* how!?, what priority? */ | |
112 | } | |
113 | ||
90e362f4 TG |
114 | static void update_curr_stop(struct rq *rq) |
115 | { | |
116 | } | |
117 | ||
34f971f6 PZ |
118 | /* |
119 | * Simple, special scheduling class for the per-CPU stop tasks: | |
120 | */ | |
43c31ac0 | 121 | DEFINE_SCHED_CLASS(stop) = { |
34f971f6 PZ |
122 | |
123 | .enqueue_task = enqueue_task_stop, | |
124 | .dequeue_task = dequeue_task_stop, | |
125 | .yield_task = yield_task_stop, | |
126 | ||
127 | .check_preempt_curr = check_preempt_curr_stop, | |
128 | ||
129 | .pick_next_task = pick_next_task_stop, | |
130 | .put_prev_task = put_prev_task_stop, | |
03b7fad1 | 131 | .set_next_task = set_next_task_stop, |
34f971f6 PZ |
132 | |
133 | #ifdef CONFIG_SMP | |
6e2df058 | 134 | .balance = balance_stop, |
21f56ffe | 135 | .pick_task = pick_task_stop, |
34f971f6 | 136 | .select_task_rq = select_task_rq_stop, |
c5b28038 | 137 | .set_cpus_allowed = set_cpus_allowed_common, |
34f971f6 PZ |
138 | #endif |
139 | ||
34f971f6 PZ |
140 | .task_tick = task_tick_stop, |
141 | ||
34f971f6 PZ |
142 | .prio_changed = prio_changed_stop, |
143 | .switched_to = switched_to_stop, | |
90e362f4 | 144 | .update_curr = update_curr_stop, |
34f971f6 | 145 | }; |