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1 | /* LTTng user-space "fast" library |
2 | * |
3 | * This daemon is spawned by each traced thread (to share the mmap). |
4 | * |
5 | * Its job is to dump periodically this buffer to disk (when it receives a |
6 | * SIGUSR1 from its parent). |
7 | * |
8 | * It uses the control information in the shared memory area (producer/consumer |
9 | * count). |
10 | * |
11 | * When the parent thread dies (yes, those thing may happen) ;) , this daemon |
12 | * will flush the last buffer and write it to disk. |
13 | * |
14 | * Supplement note for streaming : the daemon is responsible for flushing |
15 | * periodically the buffer if it is streaming data. |
16 | * |
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17 | * |
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18 | * Notes : |
19 | * shm memory is typically limited to 4096 units (system wide limit SHMMNI in |
20 | * /proc/sys/kernel/shmmni). As it requires computation time upon creation, we |
21 | * do not use it : we will use a shared mmap() instead which is passed through |
22 | * the fork(). |
23 | * MAP_SHARED mmap segment. Updated when msync or munmap are called. |
24 | * MAP_ANONYMOUS. |
25 | * Memory mapped by mmap() is preserved across fork(2), with the same |
26 | * attributes. |
27 | * |
28 | * Eventually, there will be two mode : |
29 | * * Slow thread spawn : a fork() is done for each new thread. If the process |
30 | * dies, the data is not lost. |
31 | * * Fast thread spawn : a pthread_create() is done by the application for each |
32 | * new thread. |
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33 | * Copyright 2006 Mathieu Desnoyers |
34 | * |
35 | */ |
36 | |
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37 | #include <sys/types.h> |
38 | #include <sys/wait.h> |
39 | #include <unistd.h> |
40 | #include <stdlib.h> |
41 | #include <stdio.h> |
42 | #include <signal.h> |
43 | #include <syscall.h> |
44 | #include <features.h> |
45 | #include <pthread.h> |
46 | #include <malloc.h> |
47 | #include <string.h> |
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48 | #include <sys/mman.h> |
49 | #include <signal.h> |
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50 | |
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51 | #include "ltt-usertrace-fast.h" |
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52 | |
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53 | /* TLS for the trace buffer |
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54 | * http://www.dis.com/gnu/gcc/C--98-Thread-Local-Edits.html |
55 | * |
56 | * Add after paragraph 4 |
57 | * |
58 | * The storage for an object of thread storage duration shall be statically |
59 | * initialized before the first statement of the thread startup function. An |
60 | * object of thread storage duration shall not require dynamic |
61 | * initialization. |
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62 | */ |
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63 | #if 0 |
64 | __thread struct ltt_trace_info ltt_trace_info = |
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65 | { |
66 | .init = 0, |
67 | .filter = 0, |
68 | .nesting = ATOMIC_INIT(0), |
69 | .channel.facilities = |
70 | { ATOMIC_INIT(0), |
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71 | ATOMIC_INIT(0), |
72 | ATOMIC_INIT(0), |
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73 | ATOMIC_INIT(0) |
74 | }, |
75 | .channel.cpu = |
76 | { ATOMIC_INIT(0), |
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77 | ATOMIC_INIT(0), |
78 | ATOMIC_INIT(0), |
79 | ATOMIC_INIT(0) |
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80 | }, |
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81 | }; |
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82 | #endif //0 |
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83 | |
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84 | __thread struct ltt_trace_info *thread_trace_info = NULL; |
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85 | |
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86 | |
87 | /* signal handling */ |
88 | |
89 | static void handler(int signo) |
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90 | { |
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91 | printf("Signal %d received\n", signo); |
92 | } |
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93 | |
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94 | |
95 | |
96 | void ltt_usertrace_fast_buffer_switch(void) |
97 | { |
98 | kill(thread_trace_info->daemon_id, SIGUSR1); |
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99 | } |
100 | |
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101 | static void ltt_usertrace_fast_daemon(struct ltt_trace_info *shared_trace_info, |
102 | sigset_t oldset) |
103 | { |
104 | struct sigaction act; |
105 | int ret; |
106 | |
107 | printf("ltt_usertrace_fast_daemon : init is %d, pid is %lu\n", |
108 | shared_trace_info->init, getpid()); |
109 | |
110 | act.sa_handler = handler; |
111 | act.sa_flags = 0; |
112 | sigemptyset(&(act.sa_mask)); |
113 | sigaddset(&(act.sa_mask), SIGUSR1); |
114 | sigaction(SIGUSR1, &act, NULL); |
115 | /* Enable signals */ |
116 | ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL); |
117 | if(ret) { |
118 | printf("Error in pthread_sigmask\n"); |
119 | } |
120 | |
121 | while(1) { |
122 | pause(); |
123 | printf("Doing a buffer switch read. pid is : %lu\n", getpid()); |
124 | } |
125 | |
126 | } |
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127 | |
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128 | void ltt_thread_init(void) |
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129 | { |
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130 | pid_t pid; |
131 | struct ltt_trace_info *shared_trace_info; |
132 | int ret; |
133 | sigset_t set, oldset; |
134 | |
135 | /* parent : create the shared memory map */ |
136 | shared_trace_info = thread_trace_info = mmap(0, sizeof(*thread_trace_info), |
137 | PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, 0, 0); |
138 | memset(shared_trace_info, 0, sizeof(*thread_trace_info)); |
139 | thread_trace_info->init = 1; |
140 | |
141 | /* Disable signals */ |
142 | ret = sigfillset(&set); |
143 | if(ret) { |
144 | printf("Error in sigfillset\n"); |
145 | } |
146 | |
147 | |
148 | ret = pthread_sigmask(SIG_BLOCK, &set, &oldset); |
149 | if(ret) { |
150 | printf("Error in pthread_sigmask\n"); |
151 | } |
152 | |
153 | pid = fork(); |
154 | if(pid > 0) { |
155 | /* Parent */ |
156 | thread_trace_info->daemon_id = pid; |
157 | |
158 | /* Enable signals */ |
159 | ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL); |
160 | if(ret) { |
161 | printf("Error in pthread_sigmask\n"); |
162 | } |
163 | } else if(pid == 0) { |
164 | /* Child */ |
165 | ltt_usertrace_fast_daemon(shared_trace_info, oldset); |
166 | /* Should never return */ |
167 | exit(-1); |
168 | } else if(pid < 0) { |
169 | /* fork error */ |
170 | perror("Error in forking ltt-usertrace-fast"); |
171 | } |
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172 | } |
173 | |
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174 | void __attribute__((constructor)) __ltt_usertrace_fast_init(void) |
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175 | { |
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176 | printf("LTT usertrace-fast init\n"); |
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177 | |
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178 | ltt_thread_init(); |
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179 | } |
180 | |
181 | void __attribute__((destructor)) __ltt_usertrace_fast_fini(void) |
182 | { |
183 | printf("LTT usertrace-fast fini\n"); |
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184 | |
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185 | } |
186 | |