-
-/* LTTng user-space "fast" tracing code
+/* LTTng user-space "fast" library
+ *
+ * This daemon is spawned by each traced thread (to share the mmap).
+ *
+ * Its job is to dump periodically this buffer to disk (when it receives a
+ * SIGUSR1 from its parent).
+ *
+ * It uses the control information in the shared memory area (producer/consumer
+ * count).
+ *
+ * When the parent thread dies (yes, those thing may happen) ;) , this daemon
+ * will flush the last buffer and write it to disk.
*
+ * Supplement note for streaming : the daemon is responsible for flushing
+ * periodically the buffer if it is streaming data.
+ *
+ *
+ * Notes :
+ * shm memory is typically limited to 4096 units (system wide limit SHMMNI in
+ * /proc/sys/kernel/shmmni). As it requires computation time upon creation, we
+ * do not use it : we will use a shared mmap() instead which is passed through
+ * the fork().
+ * MAP_SHARED mmap segment. Updated when msync or munmap are called.
+ * MAP_ANONYMOUS.
+ * Memory mapped by mmap() is preserved across fork(2), with the same
+ * attributes.
+ *
+ * Eventually, there will be two mode :
+ * * Slow thread spawn : a fork() is done for each new thread. If the process
+ * dies, the data is not lost.
+ * * Fast thread spawn : a pthread_create() is done by the application for each
+ * new thread.
* Copyright 2006 Mathieu Desnoyers
*
*/
-
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <pthread.h>
#include <malloc.h>
#include <string.h>
+#include <sys/mman.h>
+#include <signal.h>
#include "ltt-usertrace-fast.h"
-/* TLS for the trace buffer
- * http://www.dis.com/gnu/gcc/C--98-Thread-Local-Edits.html
- *
- * Add after paragraph 4
- *
- * The storage for an object of thread storage duration shall be statically
- * initialized before the first statement of the thread startup function. An
- * object of thread storage duration shall not require dynamic
- * initialization.
- */
-__thread struct lttng_trace_info lttng_trace_info =
+/* Writer (the traced application) */
+
+__thread struct ltt_trace_info *thread_trace_info = NULL;
+
+void ltt_usertrace_fast_buffer_switch(void)
{
- .init = 0,
- .filter = 0,
- .nesting = ATOMIC_INIT(0),
- .channel.facilities =
- { ATOMIC_INIT(0),
- ATOMIC_INIT(0),
- ATOMIC_INIT(0),
- ATOMIC_INIT(0)
- },
- .channel.cpu =
- { ATOMIC_INIT(0),
- ATOMIC_INIT(0),
- ATOMIC_INIT(0),
- ATOMIC_INIT(0)
- },
-};
-
-
-static void ltt_cleanup_thread(void *arg)
+ kill(thread_trace_info->daemon_id, SIGUSR1);
+}
+
+static void ltt_usertrace_fast_cleanup(void *arg)
{
- /* Flush the data in the lttng_trace_info */
+ kill(thread_trace_info->daemon_id, SIGUSR2);
+}
+
+/* Reader (the disk dumper daemon) */
+
+static pid_t ppid = 0;
+static int parent_exited = 0;
+/* signal handling */
+static void handler_sigusr1(int signo)
+{
+ printf("LTT Signal %d received : parent buffer switch.\n", signo);
}
+static void handler_sigusr2(int signo)
+{
+ printf("LTT Signal %d received : parent exited.\n", signo);
+ parent_exited = 1;
+}
-void ltt_thread_init(void)
+static void handler_sigalarm(int signo)
{
- _pthread_cleanup_push(<tng_trace_info.cleanup,
- ltt_cleanup_thread, NULL);
+ printf("LTT Signal %d received\n", signo);
+
+ if(getppid() != ppid) {
+ /* Parent died */
+ printf("LTT Parent %lu died, cleaning up\n", ppid);
+ ppid = 0;
+ }
+ alarm(3);
}
-void __attribute__((constructor)) __ltt_usertrace_fast_init(void)
+/* This function is called by ltt_thread_init which has signals blocked */
+static void ltt_usertrace_fast_daemon(struct ltt_trace_info *shared_trace_info,
+ sigset_t oldset)
{
- int err;
+ struct sigaction act;
+ int ret;
+
+ ppid = getppid();
+
+ printf("LTT ltt_usertrace_fast_daemon : init is %d, pid is %lu\n",
+ shared_trace_info->init, getpid());
+
+ act.sa_handler = handler_sigusr1;
+ act.sa_flags = 0;
+ sigemptyset(&(act.sa_mask));
+ sigaddset(&(act.sa_mask), SIGUSR1);
+ sigaction(SIGUSR1, &act, NULL);
+
+ act.sa_handler = handler_sigusr2;
+ act.sa_flags = 0;
+ sigemptyset(&(act.sa_mask));
+ sigaddset(&(act.sa_mask), SIGUSR2);
+ sigaction(SIGUSR2, &act, NULL);
+
+ act.sa_handler = handler_sigalarm;
+ act.sa_flags = 0;
+ sigemptyset(&(act.sa_mask));
+ sigaddset(&(act.sa_mask), SIGALRM);
+ sigaction(SIGALRM, &act, NULL);
+
+ /* Enable signals */
+ ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+ if(ret) {
+ printf("LTT Error in pthread_sigmask\n");
+ }
+
+ alarm(3);
+
+ while(1) {
+ pause();
+ if(ppid == 0) break; /* parent died */
+ if(parent_exited) break;
+ printf("LTT Doing a buffer switch read. pid is : %lu\n", getpid());
+ //printf("Test parent. pid is : %lu, ppid is %lu\n", getpid(), getppid());
+ }
+
+ /* Buffer force switch (flush) */
+ //TODO
+
+ /* The parent thread is dead and we have finished with the buffer */
+ munmap(shared_trace_info, sizeof(*shared_trace_info));
+
+ exit(0);
+}
+
- printf("LTTng usertrace-fast init\n");
+/* Reader-writer initialization */
+
+static enum ltt_process_role { LTT_ROLE_WRITER, LTT_ROLE_READER }
+ role = LTT_ROLE_WRITER;
+
+
+void ltt_rw_init(void)
+{
+ pid_t pid;
+ struct ltt_trace_info *shared_trace_info;
+ int ret;
+ sigset_t set, oldset;
+
+ /* parent : create the shared memory map */
+ shared_trace_info = thread_trace_info = mmap(0, sizeof(*thread_trace_info),
+ PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, 0, 0);
+ memset(shared_trace_info, 0, sizeof(*thread_trace_info));
+ thread_trace_info->init = 1;
+
+ /* Disable signals */
+ ret = sigfillset(&set);
+ if(ret) {
+ printf("LTT Error in sigfillset\n");
+ }
+
+
+ ret = pthread_sigmask(SIG_BLOCK, &set, &oldset);
+ if(ret) {
+ printf("LTT Error in pthread_sigmask\n");
+ }
+
+ pid = fork();
+ if(pid > 0) {
+ /* Parent */
+ thread_trace_info->daemon_id = pid;
+
+ /* Enable signals */
+ ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+ if(ret) {
+ printf("LTT Error in pthread_sigmask\n");
+ }
+ } else if(pid == 0) {
+ /* Child */
+ role = LTT_ROLE_READER;
+ ltt_usertrace_fast_daemon(shared_trace_info, oldset);
+ /* Should never return */
+ exit(-1);
+ } else if(pid < 0) {
+ /* fork error */
+ perror("LTT Error in forking ltt-usertrace-fast");
+ }
+}
- ltt_thread_init();
+static __thread struct _pthread_cleanup_buffer cleanup_buffer;
+void ltt_thread_init(void)
+{
+ _pthread_cleanup_push(&cleanup_buffer, ltt_usertrace_fast_cleanup, NULL);
+ ltt_rw_init();
+}
+
+void __attribute__((constructor)) __ltt_usertrace_fast_init(void)
+{
+ printf("LTT usertrace-fast init\n");
+
+ ltt_rw_init();
+}
+
+void __attribute__((destructor)) __ltt_usertrace_fast_fini(void)
+{
+ if(role == LTT_ROLE_WRITER) {
+ printf("LTT usertrace-fast fini\n");
+ ltt_usertrace_fast_cleanup(NULL);
+ }
}
projects / lttv.git / blobdiff