-
-/* 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.
+ *
+ * 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
*
*/
-
+#define _GNU_SOURCE
+#define LTT_TRACE
#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 <sys/stat.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <sys/param.h>
+#include <sys/time.h>
+#include <errno.h>
-#include "ltt_usertrace.h"
+#include <asm/atomic.h>
+#include <asm/timex.h> //for get_cycles()
-/* 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.
- */
+_syscall0(pid_t,gettid)
+
+#include "ltt-usertrace-fast.h"
+
+enum force_switch_mode { FORCE_ACTIVE, FORCE_FLUSH };
+
+/* 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));
+ }
+}
-__thread struct lttng_trace_info lttng_trace_info =
+/* Reader (the disk dumper daemon) */
+
+static pid_t traced_pid = 0;
+static pid_t traced_tid = 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)
{
- .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)
+ printf("LTT Signal %d received : parent exited.\n", signo);
+ parent_exited = 1;
+}
+
+static void handler_sigalarm(int signo)
{
- /* Flush the data in the lttng_trace_info */
+ 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);
}
+/* Do a buffer switch. Don't switch if buffer is completely empty */
+static void flush_buffer(struct ltt_buf *ltt_buf, enum force_switch_mode mode)
+{
+ uint64_t tsc;
+ int offset_begin, offset_end, offset_old;
+ int reserve_commit_diff;
+ int consumed_old, consumed_new;
+ int commit_count, reserve_count;
+ int end_switch_old;
-void ltt_thread_init(void)
+ do {
+ offset_old = atomic_read(<t_buf->offset);
+ offset_begin = offset_old;
+ end_switch_old = 0;
+ tsc = ltt_get_timestamp();
+ if(tsc == 0) {
+ /* Error in getting the timestamp : should not happen : it would
+ * mean we are called from an NMI during a write seqlock on xtime. */
+ return;
+ }
+
+ if(SUBBUF_OFFSET(offset_begin, ltt_buf) != 0) {
+ offset_begin = SUBBUF_ALIGN(offset_begin, ltt_buf);
+ end_switch_old = 1;
+ } else {
+ /* we do not have to switch : buffer is empty */
+ return;
+ }
+ if(mode == FORCE_ACTIVE)
+ offset_begin += ltt_subbuf_header_len(ltt_buf);
+ /* Always begin_switch in FORCE_ACTIVE mode */
+
+ /* Test new buffer integrity */
+ reserve_commit_diff =
+ atomic_read(
+ <t_buf->reserve_count[SUBBUF_INDEX(offset_begin, ltt_buf)])
+ - atomic_read(
+ <t_buf->commit_count[SUBBUF_INDEX(offset_begin, ltt_buf)]);
+ if(reserve_commit_diff == 0) {
+ /* Next buffer not corrupted. */
+ if(mode == FORCE_ACTIVE
+ && (offset_begin-atomic_read(<t_buf->consumed))
+ >= ltt_buf->alloc_size) {
+ /* We do not overwrite non consumed buffers and we are full : ignore
+ switch while tracing is active. */
+ return;
+ }
+ } else {
+ /* Next subbuffer corrupted. Force pushing reader even in normal mode */
+ }
+
+ offset_end = offset_begin;
+ } while(atomic_cmpxchg(<t_buf->offset, offset_old, offset_end)
+ != offset_old);
+
+
+ if(mode == FORCE_ACTIVE) {
+ /* Push the reader if necessary */
+ do {
+ consumed_old = atomic_read(<t_buf->consumed);
+ /* If buffer is in overwrite mode, push the reader consumed count if
+ the write position has reached it and we are not at the first
+ iteration (don't push the reader farther than the writer).
+ This operation can be done concurrently by many writers in the
+ same buffer, the writer being at the fartest write position sub-buffer
+ index in the buffer being the one which will win this loop. */
+ /* If the buffer is not in overwrite mode, pushing the reader only
+ happen if a sub-buffer is corrupted */
+ if((SUBBUF_TRUNC(offset_end, ltt_buf)
+ - SUBBUF_TRUNC(consumed_old, ltt_buf))
+ >= ltt_buf->alloc_size)
+ consumed_new = SUBBUF_ALIGN(consumed_old, ltt_buf);
+ else {
+ consumed_new = consumed_old;
+ break;
+ }
+ } while(atomic_cmpxchg(<t_buf->consumed, consumed_old, consumed_new)
+ != consumed_old);
+
+ if(consumed_old != consumed_new) {
+ /* Reader pushed : we are the winner of the push, we can therefore
+ reequilibrate reserve and commit. Atomic increment of the commit
+ count permits other writers to play around with this variable
+ before us. We keep track of corrupted_subbuffers even in overwrite
+ mode :
+ we never want to write over a non completely committed sub-buffer :
+ possible causes : the buffer size is too low compared to the unordered
+ data input, or there is a writer who died between the reserve and the
+ commit. */
+ if(reserve_commit_diff) {
+ /* We have to alter the sub-buffer commit count : a sub-buffer is
+ corrupted */
+ atomic_add(reserve_commit_diff,
+ <t_buf->commit_count[SUBBUF_INDEX(offset_begin, ltt_buf)]);
+ atomic_inc(<t_buf->corrupted_subbuffers);
+ }
+ }
+ }
+
+ /* Always switch */
+
+ if(end_switch_old) {
+ /* old subbuffer */
+ /* Concurrency safe because we are the last and only thread to alter this
+ sub-buffer. As long as it is not delivered and read, no other thread can
+ alter the offset, alter the reserve_count or call the
+ client_buffer_end_callback on this sub-buffer.
+ The only remaining threads could be the ones with pending commits. They
+ will have to do the deliver themself.
+ Not concurrency safe in overwrite mode. We detect corrupted subbuffers with
+ commit and reserve counts. We keep a corrupted sub-buffers count and push
+ the readers across these sub-buffers.
+ Not concurrency safe if a writer is stalled in a subbuffer and
+ another writer switches in, finding out it's corrupted. The result will be
+ than the old (uncommited) subbuffer will be declared corrupted, and that
+ the new subbuffer will be declared corrupted too because of the commit
+ count adjustment.
+ Offset old should never be 0. */
+ ltt_buffer_end_callback(ltt_buf, tsc, offset_old,
+ SUBBUF_INDEX((offset_old), ltt_buf));
+ /* Setting this reserve_count will allow the sub-buffer to be delivered by
+ the last committer. */
+ reserve_count = atomic_add_return((SUBBUF_OFFSET((offset_old-1),
+ ltt_buf) + 1),
+ <t_buf->reserve_count[SUBBUF_INDEX((offset_old),
+ ltt_buf)]);
+ if(reserve_count == atomic_read(
+ <t_buf->commit_count[SUBBUF_INDEX((offset_old), ltt_buf)])) {
+ ltt_deliver_callback(ltt_buf, SUBBUF_INDEX((offset_old), ltt_buf), NULL);
+ }
+ }
+
+ if(mode == FORCE_ACTIVE) {
+ /* New sub-buffer */
+ /* This code can be executed unordered : writers may already have written
+ to the sub-buffer before this code gets executed, caution. */
+ /* The commit makes sure that this code is executed before the deliver
+ of this sub-buffer */
+ ltt_buffer_begin_callback(ltt_buf, tsc, SUBBUF_INDEX(offset_begin, ltt_buf));
+ commit_count = atomic_add_return(ltt_subbuf_header_len(ltt_buf),
+ <t_buf->commit_count[SUBBUF_INDEX(offset_begin, ltt_buf)]);
+ /* Check if the written buffer has to be delivered */
+ if(commit_count == atomic_read(
+ <t_buf->reserve_count[SUBBUF_INDEX(offset_begin, ltt_buf)])) {
+ ltt_deliver_callback(ltt_buf, SUBBUF_INDEX(offset_begin, ltt_buf), NULL);
+ }
+ }
+
+}
+
+static inline int ltt_buffer_get(struct ltt_buf *ltt_buf,
+ unsigned int *offset)
{
- _pthread_cleanup_push(<tng_trace_info.cleanup,
- ltt_cleanup_thread, NULL);
+ 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;
-void __attribute__((constructor)) __ltt_usertrace_fast_init(void)
+ 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((unsigned long)<t_buf->full,
+ FUTEX_WAKE, 1, 0, 0, 0);
+ if(ret != 1) {
+ printf("LTT warning : race condition : writer not waiting or too many writers\n");
+ }
+ atomic_set(<t_buf->full, 0);
+ }
+ }
+}
+
+static int read_subbuffer(struct ltt_buf *ltt_buf, int fd)
{
+ unsigned int consumed_old;
int err;
+ printf("LTT read buffer\n");
+
+
+ err = ltt_buffer_get(ltt_buf, &consumed_old);
+ if(err != 0) {
+ if(err != -EAGAIN) 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(ltt_buf, consumed_old);
+
+ if(err != 0) {
+ if(err == -EIO) {
+ printf("Reader has been pushed by the writer, last subbuffer corrupted.\n");
+ /* 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, pid_t l_traced_pid, pthread_t l_traced_tid)
+{
+ struct sigaction act;
+ int ret;
+ int fd_fac;
+ int fd_cpu;
+ char outfile_name[PATH_MAX];
+ char identifier_name[PATH_MAX];
+
+
+ traced_pid = l_traced_pid;
+ traced_tid = l_traced_tid;
+
+ printf("LTT ltt_usertrace_fast_daemon : init is %d, pid is %lu, traced_pid is %lu, traced_tid is %lu\n",
+ shared_trace_info->init, getpid(), traced_pid, traced_tid);
+
+ 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);
+
+ /* 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_tid, traced_pid, 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();
+ 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_subbuffer(&shared_trace_info->channel.cpu, fd_cpu);
+ } while(ret == 0);
+
+ do {
+ ret = read_subbuffer(&shared_trace_info->channel.facilities, fd_fac);
+ } while(ret == 0);
+ }
+
+ /* The parent thread is dead and we have finished with the buffer */
+
+ /* Buffer force switch (flush). Using FLUSH instead of ACTIVE because we know
+ * there is no writer. */
+ flush_buffer(&shared_trace_info->channel.cpu, FORCE_FLUSH);
+ do {
+ ret = read_subbuffer(&shared_trace_info->channel.cpu, fd_cpu);
+ } while(ret == 0);
- printf("LTTng usertrace-fast init\n");
+ flush_buffer(&shared_trace_info->channel.facilities, FORCE_FLUSH);
+ do {
+ ret = read_subbuffer(&shared_trace_info->channel.facilities, fd_fac);
+ } while(ret == 0);
+ close(fd_fac);
+ close(fd_cpu);
+
+ munmap(shared_trace_info, sizeof(*shared_trace_info));
+
+ exit(0);
+}
+
+
+/* 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();
+ pid_t l_traced_tid = gettid();
+
+ /* parent : create the shared memory map */
+ 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(*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;
+ shared_trace_info->channel.facilities.start =
+ shared_trace_info->channel.facilities_buf;
+ ltt_buffer_begin_callback(&shared_trace_info->channel.facilities,
+ ltt_get_timestamp(), 0);
+
+ 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->channel.cpu.start = shared_trace_info->channel.cpu_buf;
+ ltt_buffer_begin_callback(&shared_trace_info->channel.cpu,
+ ltt_get_timestamp(), 0);
+
+ shared_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 */
+ shared_trace_info->daemon_id = pid;
+ thread_trace_info = shared_trace_info;
+
+ /* 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, l_traced_pid,
+ l_traced_tid);
+ /* Should never return */
+ exit(-1);
+ } else if(pid < 0) {
+ /* fork error */
+ 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_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