700d350d |
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 | * |
34 | * We use a timer to check periodically if the parent died. I think it is less |
35 | * intrusive than a ptrace() on the parent, which would get every signal. The |
36 | * side effect of this is that we won't be notified if the parent does an |
37 | * exec(). In this case, we will just sit there until the parent exits. |
38 | * |
39 | * |
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40 | * Copyright 2006 Mathieu Desnoyers |
41 | * |
42 | */ |
43 | |
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44 | #include <sys/types.h> |
45 | #include <sys/wait.h> |
46 | #include <unistd.h> |
47 | #include <stdlib.h> |
48 | #include <stdio.h> |
49 | #include <signal.h> |
50 | #include <syscall.h> |
51 | #include <features.h> |
52 | #include <pthread.h> |
53 | #include <malloc.h> |
54 | #include <string.h> |
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55 | #include <sys/mman.h> |
56 | #include <signal.h> |
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57 | |
1c48e587 |
58 | #include "ltt-usertrace-fast.h" |
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59 | |
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60 | |
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61 | /* Writer (the traced application) */ |
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62 | |
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63 | __thread struct ltt_trace_info *thread_trace_info = NULL; |
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64 | |
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65 | void ltt_usertrace_fast_buffer_switch(void) |
66 | { |
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67 | struct ltt_trace_info *tmp = thread_trace_info; |
68 | if(tmp) |
69 | kill(tmp->daemon_id, SIGUSR1); |
e8efa18d |
70 | } |
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71 | |
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72 | static void ltt_usertrace_fast_cleanup(void *arg) |
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73 | { |
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74 | struct ltt_trace_info *tmp = thread_trace_info; |
75 | if(tmp) { |
76 | thread_trace_info = NULL; |
77 | kill(tmp->daemon_id, SIGUSR2); |
78 | munmap(tmp, sizeof(*tmp)); |
79 | } |
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80 | } |
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81 | |
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82 | /* Reader (the disk dumper daemon) */ |
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83 | |
a85b8f41 |
84 | static pid_t traced_pid = 0; |
e8efa18d |
85 | static int parent_exited = 0; |
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86 | |
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87 | /* signal handling */ |
88 | static void handler_sigusr1(int signo) |
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89 | { |
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90 | printf("LTT Signal %d received : parent buffer switch.\n", signo); |
e8efa18d |
91 | } |
92 | |
93 | static void handler_sigusr2(int signo) |
94 | { |
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95 | printf("LTT Signal %d received : parent exited.\n", signo); |
e8efa18d |
96 | parent_exited = 1; |
97 | } |
98 | |
99 | static void handler_sigalarm(int signo) |
100 | { |
a35eaa9c |
101 | printf("LTT Signal %d received\n", signo); |
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102 | |
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103 | if(getppid() != traced_pid) { |
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104 | /* Parent died */ |
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105 | printf("LTT Parent %lu died, cleaning up\n", traced_pid); |
106 | traced_pid = 0; |
e8efa18d |
107 | } |
108 | alarm(3); |
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109 | } |
110 | |
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111 | |
a85b8f41 |
112 | /* This function is called by ltt_rw_init which has signals blocked */ |
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113 | static void ltt_usertrace_fast_daemon(struct ltt_trace_info *shared_trace_info, |
a85b8f41 |
114 | sigset_t oldset, pid_t l_traced_pid) |
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115 | { |
116 | struct sigaction act; |
117 | int ret; |
118 | |
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119 | traced_pid = l_traced_pid; |
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120 | |
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121 | printf("LTT ltt_usertrace_fast_daemon : init is %d, pid is %lu, traced_pid is %lu\n", |
122 | shared_trace_info->init, getpid(), traced_pid); |
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123 | |
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124 | act.sa_handler = handler_sigusr1; |
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125 | act.sa_flags = 0; |
126 | sigemptyset(&(act.sa_mask)); |
127 | sigaddset(&(act.sa_mask), SIGUSR1); |
128 | sigaction(SIGUSR1, &act, NULL); |
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129 | |
130 | act.sa_handler = handler_sigusr2; |
131 | act.sa_flags = 0; |
132 | sigemptyset(&(act.sa_mask)); |
133 | sigaddset(&(act.sa_mask), SIGUSR2); |
134 | sigaction(SIGUSR2, &act, NULL); |
135 | |
136 | act.sa_handler = handler_sigalarm; |
137 | act.sa_flags = 0; |
138 | sigemptyset(&(act.sa_mask)); |
139 | sigaddset(&(act.sa_mask), SIGALRM); |
140 | sigaction(SIGALRM, &act, NULL); |
141 | |
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142 | /* Enable signals */ |
143 | ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL); |
144 | if(ret) { |
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145 | printf("LTT Error in pthread_sigmask\n"); |
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146 | } |
147 | |
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148 | alarm(3); |
149 | |
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150 | while(1) { |
151 | pause(); |
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152 | if(traced_pid == 0) break; /* parent died */ |
e8efa18d |
153 | if(parent_exited) break; |
a35eaa9c |
154 | printf("LTT Doing a buffer switch read. pid is : %lu\n", getpid()); |
e8efa18d |
155 | //printf("Test parent. pid is : %lu, ppid is %lu\n", getpid(), getppid()); |
700d350d |
156 | } |
157 | |
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158 | /* Buffer force switch (flush) */ |
159 | //TODO |
160 | |
161 | /* The parent thread is dead and we have finished with the buffer */ |
162 | munmap(shared_trace_info, sizeof(*shared_trace_info)); |
163 | |
164 | exit(0); |
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165 | } |
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166 | |
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167 | |
168 | /* Reader-writer initialization */ |
169 | |
170 | static enum ltt_process_role { LTT_ROLE_WRITER, LTT_ROLE_READER } |
171 | role = LTT_ROLE_WRITER; |
172 | |
173 | |
174 | void ltt_rw_init(void) |
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175 | { |
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176 | pid_t pid; |
177 | struct ltt_trace_info *shared_trace_info; |
178 | int ret; |
179 | sigset_t set, oldset; |
a85b8f41 |
180 | pid_t l_traced_pid = getpid(); |
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181 | |
182 | /* parent : create the shared memory map */ |
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183 | shared_trace_info = mmap(0, sizeof(*thread_trace_info), |
700d350d |
184 | PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, 0, 0); |
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185 | memset(shared_trace_info, 0, sizeof(*shared_trace_info)); |
186 | shared_trace_info->init = 1; |
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187 | |
188 | /* Disable signals */ |
189 | ret = sigfillset(&set); |
190 | if(ret) { |
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191 | printf("LTT Error in sigfillset\n"); |
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192 | } |
193 | |
194 | |
195 | ret = pthread_sigmask(SIG_BLOCK, &set, &oldset); |
196 | if(ret) { |
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197 | printf("LTT Error in pthread_sigmask\n"); |
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198 | } |
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199 | |
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200 | pid = fork(); |
201 | if(pid > 0) { |
202 | /* Parent */ |
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203 | shared_trace_info->daemon_id = pid; |
204 | thread_trace_info = shared_trace_info; |
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205 | |
206 | /* Enable signals */ |
207 | ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL); |
208 | if(ret) { |
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209 | printf("LTT Error in pthread_sigmask\n"); |
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210 | } |
211 | } else if(pid == 0) { |
212 | /* Child */ |
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213 | role = LTT_ROLE_READER; |
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214 | ltt_usertrace_fast_daemon(shared_trace_info, oldset, l_traced_pid); |
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215 | /* Should never return */ |
216 | exit(-1); |
217 | } else if(pid < 0) { |
218 | /* fork error */ |
a35eaa9c |
219 | perror("LTT Error in forking ltt-usertrace-fast"); |
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220 | } |
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221 | } |
222 | |
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223 | static __thread struct _pthread_cleanup_buffer cleanup_buffer; |
224 | |
225 | void ltt_thread_init(void) |
226 | { |
227 | _pthread_cleanup_push(&cleanup_buffer, ltt_usertrace_fast_cleanup, NULL); |
228 | ltt_rw_init(); |
229 | } |
230 | |
04180f7f |
231 | void __attribute__((constructor)) __ltt_usertrace_fast_init(void) |
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232 | { |
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233 | printf("LTT usertrace-fast init\n"); |
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234 | |
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235 | ltt_rw_init(); |
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236 | } |
237 | |
238 | void __attribute__((destructor)) __ltt_usertrace_fast_fini(void) |
239 | { |
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240 | if(role == LTT_ROLE_WRITER) { |
241 | printf("LTT usertrace-fast fini\n"); |
242 | ltt_usertrace_fast_cleanup(NULL); |
243 | } |
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244 | } |
245 | |