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  *
  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  *
  40  * Copyright 2006 Mathieu Desnoyers
  41  *
  42  */
  43
  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>
  55 #include <sys/mman.h>
  56 #include <signal.h>
  57 #include <sys/stat.h>
  58 #include <fcntl.h>
  59 #include <stdlib.h>
  60 #include <sys/param.h>
  61
  62 #include <asm/timex.h>  //for get_cycles()
  63
  64 #include "ltt-usertrace-fast.h"
  65
  66
  67 /* Writer (the traced application) */
  68
  69 __thread struct ltt_trace_info *thread_trace_info = NULL;
  70
  71 void ltt_usertrace_fast_buffer_switch(void)
  72 {
  73         struct ltt_trace_info *tmp = thread_trace_info;
  74         if(tmp)
  75                 kill(tmp->daemon_id, SIGUSR1);
  76 }
  77
  78 /* The cleanup should never be called from a signal handler */
  79 static void ltt_usertrace_fast_cleanup(void *arg)
  80 {
  81         struct ltt_trace_info *tmp = thread_trace_info;
  82         if(tmp) {
  83                 thread_trace_info = NULL;
  84                 kill(tmp->daemon_id, SIGUSR2);
  85                 munmap(tmp, sizeof(*tmp));
  86         }
  87 }
  88
  89 /* Reader (the disk dumper daemon) */
  90
  91 static pid_t traced_pid = 0;
  92 static pthread_t traced_thread = 0;
  93 static int parent_exited = 0;
  94
  95 /* signal handling */
  96 static void handler_sigusr1(int signo)
  97 {
  98         printf("LTT Signal %d received : parent buffer switch.\n", signo);
  99 }
 100
 101 static void handler_sigusr2(int signo)
 102 {
 103         printf("LTT Signal %d received : parent exited.\n", signo);
 104         parent_exited = 1;
 105 }
 106
 107 static void handler_sigalarm(int signo)
 108 {
 109         printf("LTT Signal %d received\n", signo);
 110
 111         if(getppid() != traced_pid) {
 112                 /* Parent died */
 113                 printf("LTT Parent %lu died, cleaning up\n", traced_pid);
 114                 traced_pid = 0;
 115         }
 116         alarm(3);
 117 }
 118
 119
 120 /* This function is called by ltt_rw_init which has signals blocked */
 121 static void ltt_usertrace_fast_daemon(struct ltt_trace_info *shared_trace_info,
 122                 sigset_t oldset, pid_t l_traced_pid, pthread_t l_traced_thread)
 123 {
 124         struct sigaction act;
 125         int ret;
 126         int fd_fac;
 127         int fd_cpu;
 128         char outfile_name[PATH_MAX];
 129         char identifier_name[PATH_MAX];
 130
 131
 132         traced_pid = l_traced_pid;
 133         traced_thread = l_traced_thread;
 134
 135         printf("LTT ltt_usertrace_fast_daemon : init is %d, pid is %lu, traced_pid is %lu\n",
 136                         shared_trace_info->init, getpid(), traced_pid);
 137
 138         act.sa_handler = handler_sigusr1;
 139         act.sa_flags = 0;
 140         sigemptyset(&(act.sa_mask));
 141         sigaddset(&(act.sa_mask), SIGUSR1);
 142         sigaction(SIGUSR1, &act, NULL);
 143
 144         act.sa_handler = handler_sigusr2;
 145         act.sa_flags = 0;
 146         sigemptyset(&(act.sa_mask));
 147         sigaddset(&(act.sa_mask), SIGUSR2);
 148         sigaction(SIGUSR2, &act, NULL);
 149
 150         act.sa_handler = handler_sigalarm;
 151         act.sa_flags = 0;
 152         sigemptyset(&(act.sa_mask));
 153         sigaddset(&(act.sa_mask), SIGALRM);
 154         sigaction(SIGALRM, &act, NULL);
 155
 156         /* Enable signals */
 157         ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 158         if(ret) {
 159                 printf("LTT Error in pthread_sigmask\n");
 160         }
 161
 162         alarm(3);
 163
 164         /* Open output files */
 165         umask(00000);
 166         ret = mkdir(LTT_USERTRACE_ROOT, 0777);
 167         if(ret < 0 && errno != EEXIST) {
 168                 perror("LTT Error in creating output (mkdir)");
 169                 exit(-1);
 170         }
 171         ret = chdir(LTT_USERTRACE_ROOT);
 172         if(ret < 0) {
 173                 perror("LTT Error in creating output (chdir)");
 174                 exit(-1);
 175         }
 176         snprintf(identifier_name, PATH_MAX-1,   "%lu.%lu.%llu",
 177                         traced_pid, traced_thread, get_cycles());
 178         snprintf(outfile_name, PATH_MAX-1,      "facilities-%s", identifier_name);
 179         fd_fac = creat(outfile_name, 0644);
 180
 181         snprintf(outfile_name, PATH_MAX-1,      "cpu-%s", identifier_name);
 182         fd_cpu = creat(outfile_name, 0644);
 183
 184
 185         while(1) {
 186                 pause();
 187                 if(traced_pid == 0) break; /* parent died */
 188                 if(parent_exited) break;
 189                 printf("LTT Doing a buffer switch read. pid is : %lu\n", getpid());
 190                 //printf("Test parent. pid is : %lu, ppid is %lu\n", getpid(), getppid());
 191         }
 192
 193         /* Buffer force switch (flush) */
 194         //TODO
 195
 196         close(fd_fac);
 197         close(fd_cpu);
 198
 199         /* The parent thread is dead and we have finished with the buffer */
 200         munmap(shared_trace_info, sizeof(*shared_trace_info));
 201
 202         exit(0);
 203 }
 204
 205
 206 /* Reader-writer initialization */
 207
 208 static enum ltt_process_role { LTT_ROLE_WRITER, LTT_ROLE_READER }
 209         role = LTT_ROLE_WRITER;
 210
 211
 212 void ltt_rw_init(void)
 213 {
 214         pid_t pid;
 215         struct ltt_trace_info *shared_trace_info;
 216         int ret;
 217         sigset_t set, oldset;
 218         pid_t l_traced_pid = getpid();
 219         pthread_t l_traced_thread = pthread_self();
 220
 221         /* parent : create the shared memory map */
 222         shared_trace_info = mmap(0, sizeof(*thread_trace_info),
 223                         PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, 0, 0);
 224         memset(shared_trace_info, 0, sizeof(*shared_trace_info));
 225         shared_trace_info->init = 1;
 226
 227         /* Disable signals */
 228   ret = sigfillset(&set);
 229   if(ret) {
 230     printf("LTT Error in sigfillset\n");
 231   }
 232
 233
 234   ret = pthread_sigmask(SIG_BLOCK, &set, &oldset);
 235   if(ret) {
 236     printf("LTT Error in pthread_sigmask\n");
 237   }
 238
 239         pid = fork();
 240         if(pid > 0) {
 241                 /* Parent */
 242                 shared_trace_info->daemon_id = pid;
 243                 thread_trace_info = shared_trace_info;
 244
 245                 /* Enable signals */
 246                 ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 247                 if(ret) {
 248                         printf("LTT Error in pthread_sigmask\n");
 249                 }
 250         } else if(pid == 0) {
 251                 /* Child */
 252                 role = LTT_ROLE_READER;
 253                 ltt_usertrace_fast_daemon(shared_trace_info, oldset, l_traced_pid,
 254                                         l_traced_thread);
 255                 /* Should never return */
 256                 exit(-1);
 257         } else if(pid < 0) {
 258                 /* fork error */
 259                 perror("LTT Error in forking ltt-usertrace-fast");
 260         }
 261 }
 262
 263 static __thread struct _pthread_cleanup_buffer cleanup_buffer;
 264
 265 void ltt_thread_init(void)
 266 {
 267         _pthread_cleanup_push(&cleanup_buffer, ltt_usertrace_fast_cleanup, NULL);
 268         ltt_rw_init();
 269 }
 270
 271 void __attribute__((constructor)) __ltt_usertrace_fast_init(void)
 272 {
 273   printf("LTT usertrace-fast init\n");
 274
 275         ltt_rw_init();
 276 }
 277
 278 void __attribute__((destructor)) __ltt_usertrace_fast_fini(void)
 279 {
 280         if(role == LTT_ROLE_WRITER) {
 281           printf("LTT usertrace-fast fini\n");
 282                 ltt_usertrace_fast_cleanup(NULL);
 283         }
 284 }
 285