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886d51a3 MD |
1 | #ifndef _LTTNG_TRACE_CLOCK_H |
2 | #define _LTTNG_TRACE_CLOCK_H | |
3 | ||
f6c19f6e | 4 | /* |
886d51a3 | 5 | * wrapper/trace-clock.h |
f6c19f6e MD |
6 | * |
7 | * Contains LTTng trace clock mapping to LTTng trace clock or mainline monotonic | |
8 | * clock. This wrapper depends on CONFIG_HIGH_RES_TIMERS=y. | |
9 | * | |
886d51a3 MD |
10 | * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
11 | * | |
12 | * This library is free software; you can redistribute it and/or | |
13 | * modify it under the terms of the GNU Lesser General Public | |
14 | * License as published by the Free Software Foundation; only | |
15 | * version 2.1 of the License. | |
16 | * | |
17 | * This library is distributed in the hope that it will be useful, | |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
20 | * Lesser General Public License for more details. | |
21 | * | |
22 | * You should have received a copy of the GNU Lesser General Public | |
23 | * License along with this library; if not, write to the Free Software | |
24 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
f6c19f6e MD |
25 | */ |
26 | ||
f6c19f6e MD |
27 | #ifdef CONFIG_HAVE_TRACE_CLOCK |
28 | #include <linux/trace-clock.h> | |
29 | #else /* CONFIG_HAVE_TRACE_CLOCK */ | |
30 | ||
31 | #include <linux/hardirq.h> | |
32 | #include <linux/ktime.h> | |
33 | #include <linux/time.h> | |
34 | #include <linux/hrtimer.h> | |
b0725207 | 35 | #include <linux/percpu.h> |
fc8216ae | 36 | #include <linux/version.h> |
b0725207 | 37 | #include <asm/local.h> |
5a2f5e92 MD |
38 | #include <lttng-kernel-version.h> |
39 | #include <lttng-clock.h> | |
40 | #include <wrapper/percpu-defs.h> | |
41 | #include <wrapper/random.h> | |
f6c19f6e | 42 | |
53c4007f | 43 | #if ((LTTNG_KERNEL_RANGE(3,10,0, 3,10,14) && !LTTNG_RHEL_KERNEL_RANGE(3,10,0,123,0,0, 3,10,14,0,0,0)) \ |
f30ae671 | 44 | || LTTNG_KERNEL_RANGE(3,11,0, 3,11,3)) |
9998f521 | 45 | #error "Linux kernels 3.10 and 3.11 introduce a deadlock in the timekeeping subsystem. Fixed by commit 7bd36014460f793c19e7d6c94dab67b0afcfcb7f \"timekeeping: Fix HRTICK related deadlock from ntp lock changes\" in Linux." |
fc8216ae MD |
46 | #endif |
47 | ||
2754583e MD |
48 | extern struct lttng_trace_clock *lttng_trace_clock; |
49 | ||
1d2aa29e MD |
50 | /* |
51 | * Upstream Linux commit 27727df240c7 ("Avoid taking lock in NMI path with | |
52 | * CONFIG_DEBUG_TIMEKEEPING") introduces a buggy ktime_get_mono_fast_ns(). | |
53 | * This is fixed by patch "timekeeping: Fix __ktime_get_fast_ns() regression". | |
54 | */ | |
2bdfbc55 MD |
55 | #if (LTTNG_KERNEL_RANGE(4,8,0, 4,8,2) \ |
56 | || LTTNG_KERNEL_RANGE(4,7,4, 4,7,8) \ | |
57 | || LTTNG_KERNEL_RANGE(4,4,20, 4,4,25) \ | |
58 | || LTTNG_KERNEL_RANGE(4,1,32, 4,1,35)) | |
5b06448b MD |
59 | #define LTTNG_CLOCK_NMI_SAFE_BROKEN |
60 | #endif | |
61 | ||
1d2aa29e | 62 | #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0) \ |
5b06448b | 63 | && !defined(LTTNG_CLOCK_NMI_SAFE_BROKEN)) |
b0725207 MD |
64 | |
65 | DECLARE_PER_CPU(local_t, lttng_last_tsc); | |
66 | ||
67 | #if (BITS_PER_LONG == 32) | |
68 | /* | |
69 | * Fixup "src_now" using the 32 LSB from "last". We need to handle overflow and | |
70 | * underflow of the 32nd bit. "last" can be above, below or equal to the 32 LSB | |
71 | * of "src_now". | |
72 | */ | |
73 | static inline u64 trace_clock_fixup(u64 src_now, u32 last) | |
74 | { | |
75 | u64 now; | |
76 | ||
77 | now = src_now & 0xFFFFFFFF00000000ULL; | |
78 | now |= (u64) last; | |
79 | /* Detect overflow or underflow between now and last. */ | |
80 | if ((src_now & 0x80000000U) && !(last & 0x80000000U)) { | |
81 | /* | |
82 | * If 32nd bit transitions from 1 to 0, and we move forward in | |
83 | * time from "now" to "last", then we have an overflow. | |
84 | */ | |
85 | if (((s32) now - (s32) last) < 0) | |
86 | now += 0x0000000100000000ULL; | |
87 | } else if (!(src_now & 0x80000000U) && (last & 0x80000000U)) { | |
88 | /* | |
89 | * If 32nd bit transitions from 0 to 1, and we move backward in | |
90 | * time from "now" to "last", then we have an underflow. | |
91 | */ | |
92 | if (((s32) now - (s32) last) > 0) | |
93 | now -= 0x0000000100000000ULL; | |
94 | } | |
95 | return now; | |
96 | } | |
97 | #else /* #if (BITS_PER_LONG == 32) */ | |
98 | /* | |
99 | * The fixup is pretty easy on 64-bit architectures: "last" is a 64-bit | |
100 | * value, so we can use last directly as current time. | |
101 | */ | |
102 | static inline u64 trace_clock_fixup(u64 src_now, u64 last) | |
103 | { | |
104 | return last; | |
105 | } | |
106 | #endif /* #else #if (BITS_PER_LONG == 32) */ | |
107 | ||
108 | /* | |
0aaa7220 | 109 | * Sometimes called with preemption enabled. Can be interrupted. |
b0725207 MD |
110 | */ |
111 | static inline u64 trace_clock_monotonic_wrapper(void) | |
112 | { | |
113 | u64 now; | |
114 | unsigned long last, result; | |
115 | local_t *last_tsc; | |
116 | ||
117 | /* Use fast nmi-safe monotonic clock provided by the Linux kernel. */ | |
0aaa7220 | 118 | preempt_disable(); |
e6b06d7d | 119 | last_tsc = lttng_this_cpu_ptr(<tng_last_tsc); |
b0725207 MD |
120 | last = local_read(last_tsc); |
121 | /* | |
122 | * Read "last" before "now". It is not strictly required, but it ensures | |
123 | * that an interrupt coming in won't artificially trigger a case where | |
124 | * "now" < "last". This kind of situation should only happen if the | |
125 | * mono_fast time source goes slightly backwards. | |
126 | */ | |
127 | barrier(); | |
128 | now = ktime_get_mono_fast_ns(); | |
129 | if (((long) now - (long) last) < 0) | |
130 | now = trace_clock_fixup(now, last); | |
131 | result = local_cmpxchg(last_tsc, last, (unsigned long) now); | |
0aaa7220 | 132 | preempt_enable(); |
b0725207 MD |
133 | if (result == last) { |
134 | /* Update done. */ | |
135 | return now; | |
136 | } else { | |
137 | /* | |
138 | * Update not done, due to concurrent update. We can use | |
139 | * "result", since it has been sampled concurrently with our | |
140 | * time read, so it should not be far from "now". | |
141 | */ | |
142 | return trace_clock_fixup(now, result); | |
143 | } | |
144 | } | |
145 | ||
146 | #else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */ | |
f6c19f6e MD |
147 | static inline u64 trace_clock_monotonic_wrapper(void) |
148 | { | |
149 | ktime_t ktime; | |
150 | ||
151 | /* | |
152 | * Refuse to trace from NMIs with this wrapper, because an NMI could | |
153 | * nest over the xtime write seqlock and deadlock. | |
154 | */ | |
155 | if (in_nmi()) | |
97ca2c54 | 156 | return (u64) -EIO; |
f6c19f6e MD |
157 | |
158 | ktime = ktime_get(); | |
cfaf9f3d | 159 | return ktime_to_ns(ktime); |
f6c19f6e | 160 | } |
b0725207 | 161 | #endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */ |
f6c19f6e | 162 | |
2754583e | 163 | static inline u64 trace_clock_read64_monotonic(void) |
f6c19f6e MD |
164 | { |
165 | return (u64) trace_clock_monotonic_wrapper(); | |
166 | } | |
167 | ||
2754583e | 168 | static inline u64 trace_clock_freq_monotonic(void) |
f6c19f6e | 169 | { |
a3ccff4f | 170 | return (u64) NSEC_PER_SEC; |
f6c19f6e MD |
171 | } |
172 | ||
2754583e | 173 | static inline int trace_clock_uuid_monotonic(char *uuid) |
f6c19f6e | 174 | { |
a82c63f1 | 175 | return wrapper_get_bootid(uuid); |
f6c19f6e MD |
176 | } |
177 | ||
2754583e MD |
178 | static inline const char *trace_clock_name_monotonic(void) |
179 | { | |
180 | return "monotonic"; | |
181 | } | |
182 | ||
183 | static inline const char *trace_clock_description_monotonic(void) | |
184 | { | |
185 | return "Monotonic Clock"; | |
186 | } | |
187 | ||
b0725207 | 188 | #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) |
f6c19f6e MD |
189 | static inline int get_trace_clock(void) |
190 | { | |
2b0e9d96 | 191 | printk_once(KERN_WARNING "LTTng: Using mainline kernel monotonic fast clock, which is NMI-safe.\n"); |
b0725207 MD |
192 | return 0; |
193 | } | |
194 | #else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */ | |
195 | static inline int get_trace_clock(void) | |
196 | { | |
2b0e9d96 | 197 | printk_once(KERN_WARNING "LTTng: Using mainline kernel monotonic clock. NMIs will not be traced.\n"); |
f6c19f6e MD |
198 | return 0; |
199 | } | |
b0725207 | 200 | #endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */ |
f6c19f6e MD |
201 | |
202 | static inline void put_trace_clock(void) | |
203 | { | |
204 | } | |
205 | ||
2754583e MD |
206 | static inline u64 trace_clock_read64(void) |
207 | { | |
208 | struct lttng_trace_clock *ltc = ACCESS_ONCE(lttng_trace_clock); | |
209 | ||
210 | if (likely(!ltc)) { | |
211 | return trace_clock_read64_monotonic(); | |
212 | } else { | |
213 | read_barrier_depends(); /* load ltc before content */ | |
214 | return ltc->read64(); | |
215 | } | |
216 | } | |
217 | ||
218 | static inline u64 trace_clock_freq(void) | |
219 | { | |
220 | struct lttng_trace_clock *ltc = ACCESS_ONCE(lttng_trace_clock); | |
221 | ||
222 | if (!ltc) { | |
223 | return trace_clock_freq_monotonic(); | |
224 | } else { | |
225 | read_barrier_depends(); /* load ltc before content */ | |
226 | return ltc->freq(); | |
227 | } | |
228 | } | |
229 | ||
230 | static inline int trace_clock_uuid(char *uuid) | |
231 | { | |
232 | struct lttng_trace_clock *ltc = ACCESS_ONCE(lttng_trace_clock); | |
233 | ||
234 | read_barrier_depends(); /* load ltc before content */ | |
235 | /* Use default UUID cb when NULL */ | |
236 | if (!ltc || !ltc->uuid) { | |
237 | return trace_clock_uuid_monotonic(uuid); | |
238 | } else { | |
239 | return ltc->uuid(uuid); | |
240 | } | |
241 | } | |
242 | ||
243 | static inline const char *trace_clock_name(void) | |
244 | { | |
245 | struct lttng_trace_clock *ltc = ACCESS_ONCE(lttng_trace_clock); | |
246 | ||
247 | if (!ltc) { | |
248 | return trace_clock_name_monotonic(); | |
249 | } else { | |
250 | read_barrier_depends(); /* load ltc before content */ | |
251 | return ltc->name(); | |
252 | } | |
253 | } | |
254 | ||
255 | static inline const char *trace_clock_description(void) | |
256 | { | |
257 | struct lttng_trace_clock *ltc = ACCESS_ONCE(lttng_trace_clock); | |
258 | ||
259 | if (!ltc) { | |
260 | return trace_clock_description_monotonic(); | |
261 | } else { | |
262 | read_barrier_depends(); /* load ltc before content */ | |
263 | return ltc->description(); | |
264 | } | |
265 | } | |
266 | ||
f6c19f6e MD |
267 | #endif /* CONFIG_HAVE_TRACE_CLOCK */ |
268 | ||
a90917c3 | 269 | #endif /* _LTTNG_TRACE_CLOCK_H */ |