usertrace-fast/ltt-usertrace-fast.c

   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