Commit | Line | Data |
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b7cdc182 | 1 | /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only) |
9f36eaed | 2 | * |
886d51a3 | 3 | * wrapper/trace-clock.h |
f6c19f6e MD |
4 | * |
5 | * Contains LTTng trace clock mapping to LTTng trace clock or mainline monotonic | |
6 | * clock. This wrapper depends on CONFIG_HIGH_RES_TIMERS=y. | |
7 | * | |
886d51a3 | 8 | * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
f6c19f6e MD |
9 | */ |
10 | ||
9f36eaed MJ |
11 | #ifndef _LTTNG_TRACE_CLOCK_H |
12 | #define _LTTNG_TRACE_CLOCK_H | |
13 | ||
f6c19f6e MD |
14 | #ifdef CONFIG_HAVE_TRACE_CLOCK |
15 | #include <linux/trace-clock.h> | |
16 | #else /* CONFIG_HAVE_TRACE_CLOCK */ | |
17 | ||
18 | #include <linux/hardirq.h> | |
19 | #include <linux/ktime.h> | |
20 | #include <linux/time.h> | |
21 | #include <linux/hrtimer.h> | |
b0725207 | 22 | #include <linux/percpu.h> |
fc8216ae | 23 | #include <linux/version.h> |
46e25482 | 24 | #include <linux/percpu-defs.h> |
b0725207 | 25 | #include <asm/local.h> |
5a2f5e92 MD |
26 | #include <lttng-kernel-version.h> |
27 | #include <lttng-clock.h> | |
a8f2d0c7 | 28 | #include <wrapper/compiler.h> |
5a2f5e92 | 29 | #include <wrapper/random.h> |
9153ad23 | 30 | #include <blacklist/timekeeping.h> |
fc8216ae | 31 | |
2754583e MD |
32 | extern struct lttng_trace_clock *lttng_trace_clock; |
33 | ||
60e1cd07 MD |
34 | /* |
35 | * We need clock values to be monotonically increasing per-cpu, which is | |
36 | * not strictly guaranteed by ktime_get_mono_fast_ns(). It is | |
37 | * straightforward to do on architectures with a 64-bit cmpxchg(), but | |
38 | * not so on architectures without 64-bit cmpxchg. For now, only enable | |
39 | * this feature on 64-bit architectures. | |
40 | */ | |
41 | ||
d0c04533 | 42 | #if BITS_PER_LONG == 64 |
60e1cd07 MD |
43 | #define LTTNG_USE_NMI_SAFE_CLOCK |
44 | #endif | |
b0725207 | 45 | |
60e1cd07 | 46 | #ifdef LTTNG_USE_NMI_SAFE_CLOCK |
b0725207 | 47 | |
60e1cd07 | 48 | DECLARE_PER_CPU(u64, lttng_last_tsc); |
b0725207 MD |
49 | |
50 | /* | |
0aaa7220 | 51 | * Sometimes called with preemption enabled. Can be interrupted. |
b0725207 MD |
52 | */ |
53 | static inline u64 trace_clock_monotonic_wrapper(void) | |
54 | { | |
60e1cd07 MD |
55 | u64 now, last, result; |
56 | u64 *last_tsc_ptr; | |
b0725207 MD |
57 | |
58 | /* Use fast nmi-safe monotonic clock provided by the Linux kernel. */ | |
0aaa7220 | 59 | preempt_disable(); |
46e25482 | 60 | last_tsc_ptr = this_cpu_ptr(<tng_last_tsc); |
60e1cd07 | 61 | last = *last_tsc_ptr; |
b0725207 MD |
62 | /* |
63 | * Read "last" before "now". It is not strictly required, but it ensures | |
64 | * that an interrupt coming in won't artificially trigger a case where | |
65 | * "now" < "last". This kind of situation should only happen if the | |
66 | * mono_fast time source goes slightly backwards. | |
67 | */ | |
68 | barrier(); | |
69 | now = ktime_get_mono_fast_ns(); | |
60e1cd07 MD |
70 | if (U64_MAX / 2 < now - last) |
71 | now = last; | |
72 | result = cmpxchg64_local(last_tsc_ptr, last, now); | |
0aaa7220 | 73 | preempt_enable(); |
b0725207 MD |
74 | if (result == last) { |
75 | /* Update done. */ | |
76 | return now; | |
77 | } else { | |
78 | /* | |
79 | * Update not done, due to concurrent update. We can use | |
80 | * "result", since it has been sampled concurrently with our | |
81 | * time read, so it should not be far from "now". | |
82 | */ | |
60e1cd07 | 83 | return result; |
b0725207 MD |
84 | } |
85 | } | |
86 | ||
60e1cd07 | 87 | #else /* #ifdef LTTNG_USE_NMI_SAFE_CLOCK */ |
f6c19f6e MD |
88 | static inline u64 trace_clock_monotonic_wrapper(void) |
89 | { | |
90 | ktime_t ktime; | |
91 | ||
92 | /* | |
93 | * Refuse to trace from NMIs with this wrapper, because an NMI could | |
94 | * nest over the xtime write seqlock and deadlock. | |
95 | */ | |
96 | if (in_nmi()) | |
97ca2c54 | 97 | return (u64) -EIO; |
f6c19f6e MD |
98 | |
99 | ktime = ktime_get(); | |
cfaf9f3d | 100 | return ktime_to_ns(ktime); |
f6c19f6e | 101 | } |
60e1cd07 | 102 | #endif /* #else #ifdef LTTNG_USE_NMI_SAFE_CLOCK */ |
f6c19f6e | 103 | |
2754583e | 104 | static inline u64 trace_clock_read64_monotonic(void) |
f6c19f6e MD |
105 | { |
106 | return (u64) trace_clock_monotonic_wrapper(); | |
107 | } | |
108 | ||
2754583e | 109 | static inline u64 trace_clock_freq_monotonic(void) |
f6c19f6e | 110 | { |
a3ccff4f | 111 | return (u64) NSEC_PER_SEC; |
f6c19f6e MD |
112 | } |
113 | ||
2754583e | 114 | static inline int trace_clock_uuid_monotonic(char *uuid) |
f6c19f6e | 115 | { |
a82c63f1 | 116 | return wrapper_get_bootid(uuid); |
f6c19f6e MD |
117 | } |
118 | ||
2754583e MD |
119 | static inline const char *trace_clock_name_monotonic(void) |
120 | { | |
121 | return "monotonic"; | |
122 | } | |
123 | ||
124 | static inline const char *trace_clock_description_monotonic(void) | |
125 | { | |
126 | return "Monotonic Clock"; | |
127 | } | |
128 | ||
60e1cd07 | 129 | #ifdef LTTNG_USE_NMI_SAFE_CLOCK |
f6c19f6e MD |
130 | static inline int get_trace_clock(void) |
131 | { | |
e36de50d | 132 | printk_once(KERN_WARNING "LTTng: Using mainline kernel monotonic fast clock, which is NMI-safe.\n"); |
b0725207 MD |
133 | return 0; |
134 | } | |
60e1cd07 | 135 | #else /* #ifdef LTTNG_USE_NMI_SAFE_CLOCK */ |
b0725207 MD |
136 | static inline int get_trace_clock(void) |
137 | { | |
e36de50d | 138 | printk_once(KERN_WARNING "LTTng: Using mainline kernel monotonic clock. NMIs will not be traced.\n"); |
f6c19f6e MD |
139 | return 0; |
140 | } | |
60e1cd07 | 141 | #endif /* #else #ifdef LTTNG_USE_NMI_SAFE_CLOCK */ |
f6c19f6e MD |
142 | |
143 | static inline void put_trace_clock(void) | |
144 | { | |
145 | } | |
146 | ||
2754583e MD |
147 | static inline u64 trace_clock_read64(void) |
148 | { | |
a8f2d0c7 | 149 | struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock); |
2754583e MD |
150 | |
151 | if (likely(!ltc)) { | |
152 | return trace_clock_read64_monotonic(); | |
153 | } else { | |
154 | read_barrier_depends(); /* load ltc before content */ | |
155 | return ltc->read64(); | |
156 | } | |
157 | } | |
158 | ||
159 | static inline u64 trace_clock_freq(void) | |
160 | { | |
a8f2d0c7 | 161 | struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock); |
2754583e MD |
162 | |
163 | if (!ltc) { | |
164 | return trace_clock_freq_monotonic(); | |
165 | } else { | |
166 | read_barrier_depends(); /* load ltc before content */ | |
167 | return ltc->freq(); | |
168 | } | |
169 | } | |
170 | ||
171 | static inline int trace_clock_uuid(char *uuid) | |
172 | { | |
a8f2d0c7 | 173 | struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock); |
2754583e MD |
174 | |
175 | read_barrier_depends(); /* load ltc before content */ | |
176 | /* Use default UUID cb when NULL */ | |
177 | if (!ltc || !ltc->uuid) { | |
178 | return trace_clock_uuid_monotonic(uuid); | |
179 | } else { | |
180 | return ltc->uuid(uuid); | |
181 | } | |
182 | } | |
183 | ||
184 | static inline const char *trace_clock_name(void) | |
185 | { | |
a8f2d0c7 | 186 | struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock); |
2754583e MD |
187 | |
188 | if (!ltc) { | |
189 | return trace_clock_name_monotonic(); | |
190 | } else { | |
191 | read_barrier_depends(); /* load ltc before content */ | |
192 | return ltc->name(); | |
193 | } | |
194 | } | |
195 | ||
196 | static inline const char *trace_clock_description(void) | |
197 | { | |
a8f2d0c7 | 198 | struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock); |
2754583e MD |
199 | |
200 | if (!ltc) { | |
201 | return trace_clock_description_monotonic(); | |
202 | } else { | |
203 | read_barrier_depends(); /* load ltc before content */ | |
204 | return ltc->description(); | |
205 | } | |
206 | } | |
207 | ||
f6c19f6e MD |
208 | #endif /* CONFIG_HAVE_TRACE_CLOCK */ |
209 | ||
a90917c3 | 210 | #endif /* _LTTNG_TRACE_CLOCK_H */ |