* dies, the data is not lost.
* * Fast thread spawn : a pthread_create() is done by the application for each
* new thread.
+ *
+ * We use a timer to check periodically if the parent died. I think it is less
+ * intrusive than a ptrace() on the parent, which would get every signal. The
+ * side effect of this is that we won't be notified if the parent does an
+ * exec(). In this case, we will just sit there until the parent exits.
+ *
+ *
* Copyright 2006 Mathieu Desnoyers
*
*/
#include <string.h>
#include <sys/mman.h>
#include <signal.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <sys/param.h>
+#include <linux/futex.h>
+#include <sys/time.h>
+
+#include <asm/timex.h> //for get_cycles()
#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.
- */
-#if 0
-__thread struct ltt_trace_info ltt_trace_info =
-{
- .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)
- },
-};
-#endif //0
+
+/* Writer (the traced application) */
__thread struct ltt_trace_info *thread_trace_info = NULL;
+void ltt_usertrace_fast_buffer_switch(void)
+{
+ struct ltt_trace_info *tmp = thread_trace_info;
+ if(tmp)
+ kill(tmp->daemon_id, SIGUSR1);
+}
+
+/* The cleanup should never be called from a signal handler */
+static void ltt_usertrace_fast_cleanup(void *arg)
+{
+ struct ltt_trace_info *tmp = thread_trace_info;
+ if(tmp) {
+ thread_trace_info = NULL;
+ kill(tmp->daemon_id, SIGUSR2);
+ munmap(tmp, sizeof(*tmp));
+ }
+}
+
+/* Reader (the disk dumper daemon) */
+
+static pid_t traced_pid = 0;
+static pthread_t traced_thread = 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(int signo)
+static void handler_sigusr2(int signo)
{
- printf("Signal %d received\n", signo);
+ printf("LTT Signal %d received : parent exited.\n", signo);
+ parent_exited = 1;
}
+static void handler_sigalarm(int signo)
+{
+ printf("LTT Signal %d received\n", signo);
+ if(getppid() != traced_pid) {
+ /* Parent died */
+ printf("LTT Parent %lu died, cleaning up\n", traced_pid);
+ traced_pid = 0;
+ }
+ alarm(3);
+}
-void ltt_usertrace_fast_buffer_switch(void)
+/* Do a buffer switch. Don't switch if buffer is completely empty */
+static void flush_buffer(struct ltt_buf *ltt_buf)
{
- kill(thread_trace_info->daemon_id, SIGUSR1);
+
+
+}
+
+static inline int ltt_buffer_get(struct ltt_buf *ltt_buf,
+ unsigned int *offset)
+{
+ unsigned int consumed_old, consumed_idx;
+ consumed_old = atomic_read(<t_buf->consumed);
+ consumed_idx = SUBBUF_INDEX(consumed_old, ltt_buf);
+
+ if(atomic_read(<t_buf->commit_count[consumed_idx])
+ != atomic_read(<t_buf->reserve_count[consumed_idx])) {
+ return -EAGAIN;
+ }
+ if((SUBBUF_TRUNC(atomic_read(<t_buf->offset), ltt_buf)
+ -SUBBUF_TRUNC(consumed_old, ltt_buf)) == 0) {
+ return -EAGAIN;
+ }
+
+ *offset = consumed_old;
+
+ return 0;
+}
+
+static inline int ltt_buffer_put(struct ltt_buf *ltt_buf,
+ unsigned int offset)
+{
+ unsigned int consumed_old, consumed_new;
+ int ret;
+
+ consumed_old = offset;
+ consumed_new = SUBBUF_ALIGN(consumed_old, ltt_buf);
+ if(atomic_cmpxchg(<t_buf->consumed, consumed_old, consumed_new)
+ != consumed_old) {
+ /* We have been pushed by the writer : the last buffer read _is_
+ * corrupted!
+ * It can also happen if this is a buffer we never got. */
+ return -EIO;
+ } else {
+ if(atomic_read(<t_buf->full) == 1) {
+ /* tell the client that buffer is now unfull */
+ ret = futex(<t_buf->full, FUTEX_WAKE, 1, NULL, NULL, 0);
+ if(ret != 1) {
+ printf("LTT warning : race condition : writer not waiting or too many writers\n");
+ }
+ atomic_set(<t_buf->full, 0);
+ }
+ }
}
+/* In the writer :
+ *
+ * if(buffer full condition) {
+ * put myself in the wait queue
+ * ltt_buf->full = 1;
+ * schedule
+ * }
+ *{
+ if(buffer_is_full) {
+ atomic_set(<t_buf->full, 1);
+ ret = futex(<t_buf->full, 1, NULL, NULL, 0);
+ }
+}
+
+ */
+
+static int read_subbuffer(struct ltt_buf *ltt_buf, int fd)
+{
+ int err;
+ printf("LTT read buffer\n");
+
+
+ err = ltt_buffer_get(&shared_trace_info->channel.cpu, &consumed_old);
+ if(err != -EAGAIN && err != 0) {
+ printf("LTT Reserving sub buffer failed\n");
+ goto get_error;
+ }
+
+ err = TEMP_FAILURE_RETRY(write(fd,
+ ltt_buf->start
+ + (consumed_old & ((ltt_buf->alloc_size)-1)),
+ ltt_buf->subbuf_size));
+
+ if(err < 0) {
+ perror("Error in writing to file");
+ goto write_error;
+ }
+#if 0
+ err = fsync(pair->trace);
+ if(err < 0) {
+ ret = errno;
+ perror("Error in writing to file");
+ goto write_error;
+ }
+#endif //0
+write_error:
+ err = ltt_buffer_put(&shared_trace_info->channel.cpu, consumed_old);
+
+ if(err != 0) {
+ if(err == -EIO) {
+ perror("Reader has been pushed by the writer, last subbuffer corrupted.");
+ /* FIXME : we may delete the last written buffer if we wish. */
+ }
+ goto get_error;
+ }
+
+get_error:
+ return err;
+}
+
+/* This function is called by ltt_rw_init which has signals blocked */
static void ltt_usertrace_fast_daemon(struct ltt_trace_info *shared_trace_info,
- sigset_t oldset)
+ sigset_t oldset, pid_t l_traced_pid, pthread_t l_traced_thread)
{
struct sigaction act;
int ret;
+ int fd_fac;
+ int fd_cpu;
+ char outfile_name[PATH_MAX];
+ char identifier_name[PATH_MAX];
- printf("ltt_usertrace_fast_daemon : init is %d, pid is %lu\n",
- shared_trace_info->init, getpid());
- act.sa_handler = handler;
+ traced_pid = l_traced_pid;
+ traced_thread = l_traced_thread;
+
+ printf("LTT ltt_usertrace_fast_daemon : init is %d, pid is %lu, traced_pid is %lu\n",
+ shared_trace_info->init, getpid(), traced_pid);
+
+ 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("Error in pthread_sigmask\n");
+ printf("LTT Error in pthread_sigmask\n");
}
+ alarm(3);
+
+ /* Open output files */
+ umask(00000);
+ ret = mkdir(LTT_USERTRACE_ROOT, 0777);
+ if(ret < 0 && errno != EEXIST) {
+ perror("LTT Error in creating output (mkdir)");
+ exit(-1);
+ }
+ ret = chdir(LTT_USERTRACE_ROOT);
+ if(ret < 0) {
+ perror("LTT Error in creating output (chdir)");
+ exit(-1);
+ }
+ snprintf(identifier_name, PATH_MAX-1, "%lu.%lu.%llu",
+ traced_pid, traced_thread, get_cycles());
+ snprintf(outfile_name, PATH_MAX-1, "facilities-%s", identifier_name);
+ fd_fac = creat(outfile_name, 0644);
+
+ snprintf(outfile_name, PATH_MAX-1, "cpu-%s", identifier_name);
+ fd_cpu = creat(outfile_name, 0644);
+
+
while(1) {
pause();
- printf("Doing a buffer switch read. pid is : %lu\n", getpid());
+ if(traced_pid == 0) break; /* parent died */
+ if(parent_exited) break;
+ printf("LTT Doing a buffer switch read. pid is : %lu\n", getpid());
+
+ do {
+ ret = read_buffer(&shared_trace_info->channel.cpu, fd_cpu);
+ } while(ret == 0);
+
+ do {
+ ret = read_buffer(&shared_trace_info->channel.facilities, fd_fac);
+ } while(ret == 0);
}
+ /* Buffer force switch (flush) */
+ flush_buffer(&shared_trace_info->channel.cpu);
+ do {
+ ret = read_buffer(&shared_trace_info->channel.cpu, fd_cpu);
+ } while(ret == 0);
+
+
+ flush_buffer(&shared_trace_info->channel.facilities);
+ do {
+ ret = read_buffer(&shared_trace_info->channel.facilities, fd_fac);
+ } while(ret == 0);
+
+ close(fd_fac);
+ close(fd_cpu);
+
+ /* The parent thread is dead and we have finished with the buffer */
+ munmap(shared_trace_info, sizeof(*shared_trace_info));
+
+ exit(0);
}
-void ltt_thread_init(void)
+
+/* 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;
+ pid_t l_traced_pid = getpid();
+ pthread_t l_traced_thread = pthread_self();
/* parent : create the shared memory map */
- shared_trace_info = thread_trace_info = mmap(0, sizeof(*thread_trace_info),
+ shared_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;
+ memset(shared_trace_info, 0, sizeof(*shared_trace_info));
+ /* Tricky semaphore : is in a shared memory space, so it's ok for a fast
+ * mutex (futex). */
+ atomic_set(&shared_trace_info->channel.facilities.full, 0);
+ shared_trace_info->channel.facilities.alloc_size = LTT_BUF_SIZE_FACILITIES;
+ shared_trace_info->channel.facilities.subbuf_size = LTT_SUBBUF_SIZE_FACILITIES;
+ atomic_set(&shared_trace_info->channel.cpu.full, 0);
+ shared_trace_info->channel.cpu.alloc_size = LTT_BUF_SIZE_CPU;
+ shared_trace_info->channel.cpu.subbuf_size = LTT_SUBBUF_SIZE_CPU;
+ shared_trace_info->init = 1;
/* Disable signals */
ret = sigfillset(&set);
if(ret) {
- printf("Error in sigfillset\n");
+ printf("LTT Error in sigfillset\n");
}
ret = pthread_sigmask(SIG_BLOCK, &set, &oldset);
if(ret) {
- printf("Error in pthread_sigmask\n");
+ printf("LTT Error in pthread_sigmask\n");
}
-
+
pid = fork();
if(pid > 0) {
/* Parent */
- thread_trace_info->daemon_id = pid;
+ shared_trace_info->daemon_id = pid;
+ thread_trace_info = shared_trace_info;
/* Enable signals */
ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
if(ret) {
- printf("Error in pthread_sigmask\n");
+ printf("LTT Error in pthread_sigmask\n");
}
} else if(pid == 0) {
/* Child */
- ltt_usertrace_fast_daemon(shared_trace_info, oldset);
+ role = LTT_ROLE_READER;
+ ltt_usertrace_fast_daemon(shared_trace_info, oldset, l_traced_pid,
+ l_traced_thread);
/* Should never return */
exit(-1);
} else if(pid < 0) {
/* fork error */
- perror("Error in forking ltt-usertrace-fast");
+ perror("LTT Error in forking ltt-usertrace-fast");
}
}
+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_thread_init();
+ ltt_rw_init();
}
void __attribute__((destructor)) __ltt_usertrace_fast_fini(void)
{
- printf("LTT usertrace-fast fini\n");
-
+ if(role == LTT_ROLE_WRITER) {
+ printf("LTT usertrace-fast fini\n");
+ ltt_usertrace_fast_cleanup(NULL);
+ }
}
projects / lttv.git / blobdiff