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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 | |
1c48e587 |
51 | #include "ltt-usertrace-fast.h" |
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52 | |
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53 | |
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54 | /* Writer (the traced application) */ |
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55 | |
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56 | __thread struct ltt_trace_info *thread_trace_info = NULL; |
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57 | |
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58 | void ltt_usertrace_fast_buffer_switch(void) |
59 | { |
60 | kill(thread_trace_info->daemon_id, SIGUSR1); |
61 | } |
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62 | |
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63 | static void ltt_usertrace_fast_cleanup(void *arg) |
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64 | { |
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65 | kill(thread_trace_info->daemon_id, SIGUSR2); |
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66 | } |
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67 | |
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68 | /* Reader (the disk dumper daemon) */ |
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69 | |
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70 | static pid_t ppid = 0; |
71 | static int parent_exited = 0; |
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72 | |
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73 | /* signal handling */ |
74 | static void handler_sigusr1(int signo) |
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75 | { |
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76 | printf("LTT Signal %d received : parent buffer switch.\n", signo); |
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77 | } |
78 | |
79 | static void handler_sigusr2(int signo) |
80 | { |
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81 | printf("LTT Signal %d received : parent exited.\n", signo); |
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82 | parent_exited = 1; |
83 | } |
84 | |
85 | static void handler_sigalarm(int signo) |
86 | { |
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87 | printf("LTT Signal %d received\n", signo); |
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88 | |
89 | if(getppid() != ppid) { |
90 | /* Parent died */ |
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91 | printf("LTT Parent %lu died, cleaning up\n", ppid); |
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92 | ppid = 0; |
93 | } |
94 | alarm(3); |
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95 | } |
96 | |
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97 | |
98 | /* This function is called by ltt_thread_init which has signals blocked */ |
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99 | static void ltt_usertrace_fast_daemon(struct ltt_trace_info *shared_trace_info, |
100 | sigset_t oldset) |
101 | { |
102 | struct sigaction act; |
103 | int ret; |
104 | |
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105 | ppid = getppid(); |
106 | |
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107 | printf("LTT ltt_usertrace_fast_daemon : init is %d, pid is %lu\n", |
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108 | shared_trace_info->init, getpid()); |
109 | |
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110 | act.sa_handler = handler_sigusr1; |
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111 | act.sa_flags = 0; |
112 | sigemptyset(&(act.sa_mask)); |
113 | sigaddset(&(act.sa_mask), SIGUSR1); |
114 | sigaction(SIGUSR1, &act, NULL); |
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115 | |
116 | act.sa_handler = handler_sigusr2; |
117 | act.sa_flags = 0; |
118 | sigemptyset(&(act.sa_mask)); |
119 | sigaddset(&(act.sa_mask), SIGUSR2); |
120 | sigaction(SIGUSR2, &act, NULL); |
121 | |
122 | act.sa_handler = handler_sigalarm; |
123 | act.sa_flags = 0; |
124 | sigemptyset(&(act.sa_mask)); |
125 | sigaddset(&(act.sa_mask), SIGALRM); |
126 | sigaction(SIGALRM, &act, NULL); |
127 | |
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128 | /* Enable signals */ |
129 | ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL); |
130 | if(ret) { |
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131 | printf("LTT Error in pthread_sigmask\n"); |
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132 | } |
133 | |
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134 | alarm(3); |
135 | |
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136 | while(1) { |
137 | pause(); |
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138 | if(ppid == 0) break; /* parent died */ |
139 | if(parent_exited) break; |
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140 | printf("LTT Doing a buffer switch read. pid is : %lu\n", getpid()); |
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141 | //printf("Test parent. pid is : %lu, ppid is %lu\n", getpid(), getppid()); |
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142 | } |
143 | |
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144 | /* Buffer force switch (flush) */ |
145 | //TODO |
146 | |
147 | /* The parent thread is dead and we have finished with the buffer */ |
148 | munmap(shared_trace_info, sizeof(*shared_trace_info)); |
149 | |
150 | exit(0); |
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151 | } |
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152 | |
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153 | |
154 | /* Reader-writer initialization */ |
155 | |
156 | static enum ltt_process_role { LTT_ROLE_WRITER, LTT_ROLE_READER } |
157 | role = LTT_ROLE_WRITER; |
158 | |
159 | |
160 | void ltt_rw_init(void) |
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161 | { |
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162 | pid_t pid; |
163 | struct ltt_trace_info *shared_trace_info; |
164 | int ret; |
165 | sigset_t set, oldset; |
166 | |
167 | /* parent : create the shared memory map */ |
168 | shared_trace_info = thread_trace_info = mmap(0, sizeof(*thread_trace_info), |
169 | PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, 0, 0); |
170 | memset(shared_trace_info, 0, sizeof(*thread_trace_info)); |
171 | thread_trace_info->init = 1; |
172 | |
173 | /* Disable signals */ |
174 | ret = sigfillset(&set); |
175 | if(ret) { |
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176 | printf("LTT Error in sigfillset\n"); |
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177 | } |
178 | |
179 | |
180 | ret = pthread_sigmask(SIG_BLOCK, &set, &oldset); |
181 | if(ret) { |
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182 | printf("LTT Error in pthread_sigmask\n"); |
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183 | } |
184 | |
185 | pid = fork(); |
186 | if(pid > 0) { |
187 | /* Parent */ |
188 | thread_trace_info->daemon_id = pid; |
189 | |
190 | /* Enable signals */ |
191 | ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL); |
192 | if(ret) { |
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193 | printf("LTT Error in pthread_sigmask\n"); |
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194 | } |
195 | } else if(pid == 0) { |
196 | /* Child */ |
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197 | role = LTT_ROLE_READER; |
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198 | ltt_usertrace_fast_daemon(shared_trace_info, oldset); |
199 | /* Should never return */ |
200 | exit(-1); |
201 | } else if(pid < 0) { |
202 | /* fork error */ |
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203 | perror("LTT Error in forking ltt-usertrace-fast"); |
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204 | } |
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205 | } |
206 | |
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207 | static __thread struct _pthread_cleanup_buffer cleanup_buffer; |
208 | |
209 | void ltt_thread_init(void) |
210 | { |
211 | _pthread_cleanup_push(&cleanup_buffer, ltt_usertrace_fast_cleanup, NULL); |
212 | ltt_rw_init(); |
213 | } |
214 | |
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215 | void __attribute__((constructor)) __ltt_usertrace_fast_init(void) |
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216 | { |
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217 | printf("LTT usertrace-fast init\n"); |
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218 | |
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219 | ltt_rw_init(); |
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220 | } |
221 | |
222 | void __attribute__((destructor)) __ltt_usertrace_fast_fini(void) |
223 | { |
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224 | if(role == LTT_ROLE_WRITER) { |
225 | printf("LTT usertrace-fast fini\n"); |
226 | ltt_usertrace_fast_cleanup(NULL); |
227 | } |
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228 | } |
229 | |