| 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 | * |
| 17 | * |
| 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. |
| 33 | * Copyright 2006 Mathieu Desnoyers |
| 34 | * |
| 35 | */ |
| 36 | |
| 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> |
| 48 | #include <sys/mman.h> |
| 49 | #include <signal.h> |
| 50 | |
| 51 | #include "ltt-usertrace-fast.h" |
| 52 | |
| 53 | |
| 54 | /* Writer (the traced application) */ |
| 55 | |
| 56 | __thread struct ltt_trace_info *thread_trace_info = NULL; |
| 57 | |
| 58 | void ltt_usertrace_fast_buffer_switch(void) |
| 59 | { |
| 60 | kill(thread_trace_info->daemon_id, SIGUSR1); |
| 61 | } |
| 62 | |
| 63 | static void ltt_usertrace_fast_cleanup(void *arg) |
| 64 | { |
| 65 | kill(thread_trace_info->daemon_id, SIGUSR2); |
| 66 | } |
| 67 | |
| 68 | /* Reader (the disk dumper daemon) */ |
| 69 | |
| 70 | static pid_t ppid = 0; |
| 71 | static int parent_exited = 0; |
| 72 | |
| 73 | /* signal handling */ |
| 74 | static void handler_sigusr1(int signo) |
| 75 | { |
| 76 | printf("LTT Signal %d received : parent buffer switch.\n", signo); |
| 77 | } |
| 78 | |
| 79 | static void handler_sigusr2(int signo) |
| 80 | { |
| 81 | printf("LTT Signal %d received : parent exited.\n", signo); |
| 82 | parent_exited = 1; |
| 83 | } |
| 84 | |
| 85 | static void handler_sigalarm(int signo) |
| 86 | { |
| 87 | printf("LTT Signal %d received\n", signo); |
| 88 | |
| 89 | if(getppid() != ppid) { |
| 90 | /* Parent died */ |
| 91 | printf("LTT Parent %lu died, cleaning up\n", ppid); |
| 92 | ppid = 0; |
| 93 | } |
| 94 | alarm(3); |
| 95 | } |
| 96 | |
| 97 | |
| 98 | /* This function is called by ltt_thread_init which has signals blocked */ |
| 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 | |
| 105 | ppid = getppid(); |
| 106 | |
| 107 | printf("LTT ltt_usertrace_fast_daemon : init is %d, pid is %lu\n", |
| 108 | shared_trace_info->init, getpid()); |
| 109 | |
| 110 | act.sa_handler = handler_sigusr1; |
| 111 | act.sa_flags = 0; |
| 112 | sigemptyset(&(act.sa_mask)); |
| 113 | sigaddset(&(act.sa_mask), SIGUSR1); |
| 114 | sigaction(SIGUSR1, &act, NULL); |
| 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 | |
| 128 | /* Enable signals */ |
| 129 | ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL); |
| 130 | if(ret) { |
| 131 | printf("LTT Error in pthread_sigmask\n"); |
| 132 | } |
| 133 | |
| 134 | alarm(3); |
| 135 | |
| 136 | while(1) { |
| 137 | pause(); |
| 138 | if(ppid == 0) break; /* parent died */ |
| 139 | if(parent_exited) break; |
| 140 | printf("LTT Doing a buffer switch read. pid is : %lu\n", getpid()); |
| 141 | //printf("Test parent. pid is : %lu, ppid is %lu\n", getpid(), getppid()); |
| 142 | } |
| 143 | |
| 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); |
| 151 | } |
| 152 | |
| 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) |
| 161 | { |
| 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) { |
| 176 | printf("LTT Error in sigfillset\n"); |
| 177 | } |
| 178 | |
| 179 | |
| 180 | ret = pthread_sigmask(SIG_BLOCK, &set, &oldset); |
| 181 | if(ret) { |
| 182 | printf("LTT Error in pthread_sigmask\n"); |
| 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) { |
| 193 | printf("LTT Error in pthread_sigmask\n"); |
| 194 | } |
| 195 | } else if(pid == 0) { |
| 196 | /* Child */ |
| 197 | role = LTT_ROLE_READER; |
| 198 | ltt_usertrace_fast_daemon(shared_trace_info, oldset); |
| 199 | /* Should never return */ |
| 200 | exit(-1); |
| 201 | } else if(pid < 0) { |
| 202 | /* fork error */ |
| 203 | perror("LTT Error in forking ltt-usertrace-fast"); |
| 204 | } |
| 205 | } |
| 206 | |
| 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 | |
| 215 | void __attribute__((constructor)) __ltt_usertrace_fast_init(void) |
| 216 | { |
| 217 | printf("LTT usertrace-fast init\n"); |
| 218 | |
| 219 | ltt_rw_init(); |
| 220 | } |
| 221 | |
| 222 | void __attribute__((destructor)) __ltt_usertrace_fast_fini(void) |
| 223 | { |
| 224 | if(role == LTT_ROLE_WRITER) { |
| 225 | printf("LTT usertrace-fast fini\n"); |
| 226 | ltt_usertrace_fast_cleanup(NULL); |
| 227 | } |
| 228 | } |
| 229 | |