1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_CONTEXT_TRACKING_STATE_H
3 #define _LINUX_CONTEXT_TRACKING_STATE_H
4
5 #include <linux/percpu.h>
6 #include <linux/static_key.h>
7 #include <linux/context_tracking_irq.h>
8
9 /* Offset to allow distinguishing irq vs. task-based idle entry/exit. */
10 #define DYNTICK_IRQ_NONIDLE ((LONG_MAX / 2) + 1)
11
12 enum ctx_state {
13 CONTEXT_DISABLED = -1, /* returned by ct_state() if unknown */
14 CONTEXT_KERNEL = 0,
15 CONTEXT_IDLE = 1,
16 CONTEXT_USER = 2,
17 CONTEXT_GUEST = 3,
18 CONTEXT_MAX = 4,
19 };
20
21 /* Even value for idle, else odd. */
22 #define RCU_DYNTICKS_IDX CONTEXT_MAX
23
24 #define CT_STATE_MASK (CONTEXT_MAX - 1)
25 #define CT_DYNTICKS_MASK (~CT_STATE_MASK)
26
27 struct context_tracking {
28 #ifdef CONFIG_CONTEXT_TRACKING_USER
29 /*
30 * When active is false, probes are unset in order
31 * to minimize overhead: TIF flags are cleared
32 * and calls to user_enter/exit are ignored. This
33 * may be further optimized using static keys.
34 */
35 bool active;
36 int recursion;
37 #endif
38 #ifdef CONFIG_CONTEXT_TRACKING
39 atomic_t state;
40 #endif
41 #ifdef CONFIG_CONTEXT_TRACKING_IDLE
42 long dynticks_nesting; /* Track process nesting level. */
43 long dynticks_nmi_nesting; /* Track irq/NMI nesting level. */
44 #endif
45 };
46
47 #ifdef CONFIG_CONTEXT_TRACKING
48 DECLARE_PER_CPU(struct context_tracking, context_tracking);
49 #endif
50
51 #ifdef CONFIG_CONTEXT_TRACKING_USER
52 static __always_inline int __ct_state(void)
53 {
54 return raw_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
55 }
56 #endif
57
58 #ifdef CONFIG_CONTEXT_TRACKING_IDLE
59 static __always_inline int ct_dynticks(void)
60 {
61 return atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_DYNTICKS_MASK;
62 }
63
64 static __always_inline int ct_dynticks_cpu(int cpu)
65 {
66 struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
67
68 return atomic_read(&ct->state) & CT_DYNTICKS_MASK;
69 }
70
71 static __always_inline int ct_dynticks_cpu_acquire(int cpu)
72 {
73 struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
74
75 return atomic_read_acquire(&ct->state) & CT_DYNTICKS_MASK;
76 }
77
78 static __always_inline long ct_dynticks_nesting(void)
79 {
80 return __this_cpu_read(context_tracking.dynticks_nesting);
81 }
82
83 static __always_inline long ct_dynticks_nesting_cpu(int cpu)
84 {
85 struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
86
87 return ct->dynticks_nesting;
88 }
89
90 static __always_inline long ct_dynticks_nmi_nesting(void)
91 {
92 return __this_cpu_read(context_tracking.dynticks_nmi_nesting);
93 }
94
95 static __always_inline long ct_dynticks_nmi_nesting_cpu(int cpu)
96 {
97 struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
98
99 return ct->dynticks_nmi_nesting;
100 }
101 #endif /* #ifdef CONFIG_CONTEXT_TRACKING_IDLE */
102
103 #ifdef CONFIG_CONTEXT_TRACKING_USER
104 extern struct static_key_false context_tracking_key;
105
106 static __always_inline bool context_tracking_enabled(void)
107 {
108 return static_branch_unlikely(&context_tracking_key);
109 }
110
111 static __always_inline bool context_tracking_enabled_cpu(int cpu)
112 {
113 return context_tracking_enabled() && per_cpu(context_tracking.active, cpu);
114 }
115
116 static inline bool context_tracking_enabled_this_cpu(void)
117 {
118 return context_tracking_enabled() && __this_cpu_read(context_tracking.active);
119 }
120
121 /**
122 * ct_state() - return the current context tracking state if known
123 *
124 * Returns the current cpu's context tracking state if context tracking
125 * is enabled. If context tracking is disabled, returns
126 * CONTEXT_DISABLED. This should be used primarily for debugging.
127 */
128 static __always_inline int ct_state(void)
129 {
130 int ret;
131
132 if (!context_tracking_enabled())
133 return CONTEXT_DISABLED;
134
135 preempt_disable();
136 ret = __ct_state();
137 preempt_enable();
138
139 return ret;
140 }
141
142 #else
143 static __always_inline bool context_tracking_enabled(void) { return false; }
144 static __always_inline bool context_tracking_enabled_cpu(int cpu) { return false; }
145 static __always_inline bool context_tracking_enabled_this_cpu(void) { return false; }
146 #endif /* CONFIG_CONTEXT_TRACKING_USER */
147
148 #endif
149
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