Fixes #324
Signed-off-by: David Goulet <[email protected]>
---
src/bin/lttng-sessiond/consumer.h | 21 +++++-
src/bin/lttng-sessiond/main.c | 127 ++++++++++++++++++++++++++++---------
2 files changed, 116 insertions(+), 32 deletions(-)
diff --git a/src/bin/lttng-sessiond/consumer.h
b/src/bin/lttng-sessiond/consumer.h
index 1337f32..6639bd8 100644
--- a/src/bin/lttng-sessiond/consumer.h
+++ b/src/bin/lttng-sessiond/consumer.h
@@ -18,8 +18,6 @@
#ifndef _CONSUMER_H
#define _CONSUMER_H
-#include <semaphore.h>
-
#include <common/consumer.h>
#include <common/hashtable/hashtable.h>
#include <lttng/lttng.h>
@@ -54,7 +52,24 @@ struct consumer_data {
enum lttng_consumer_type type;
pthread_t thread; /* Worker thread interacting with the consumer
*/
- sem_t sem;
+
+ /* Conditions used by the consumer thread to indicate readiness. */
+ pthread_cond_t cond;
+ pthread_condattr_t condattr;
+ pthread_mutex_t cond_mutex;
+
+ /*
+ * This is a flag condition indicating that the consumer thread is ready
+ * and connected to the lttng-consumerd daemon. This flag MUST only be
+ * updated by locking the condition mutex above or before spawning a
+ * consumer thread.
+ *
+ * A value of 0 means that the thread is NOT ready. A value of 1 means
that
+ * the thread consumer did connect successfully to the lttng-consumerd
+ * daemon. A negative value indicates that there is been an error and
the
+ * thread as likely quit.
+ */
+ int consumer_thread_is_ready;
/* Mutex to control consumerd pid assignation */
pthread_mutex_t pid_mutex;
diff --git a/src/bin/lttng-sessiond/main.c b/src/bin/lttng-sessiond/main.c
index 730ac65..2fb8700 100644
--- a/src/bin/lttng-sessiond/main.c
+++ b/src/bin/lttng-sessiond/main.c
@@ -21,7 +21,6 @@
#include <grp.h>
#include <limits.h>
#include <pthread.h>
-#include <semaphore.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
@@ -81,7 +80,10 @@ static int is_root; /* Set to 1 if the
daemon is running as root */
static pid_t ppid; /* Parent PID for --sig-parent option */
static char *rundir;
-/* Consumer daemon specific control data */
+/*
+ * Consumer daemon specific control data. Every value not initialized here is
+ * set to 0 by the static definition.
+ */
static struct consumer_data kconsumer_data = {
.type = LTTNG_CONSUMER_KERNEL,
.err_unix_sock_path = DEFAULT_KCONSUMERD_ERR_SOCK_PATH,
@@ -90,6 +92,8 @@ static struct consumer_data kconsumer_data = {
.cmd_sock = -1,
.pid_mutex = PTHREAD_MUTEX_INITIALIZER,
.lock = PTHREAD_MUTEX_INITIALIZER,
+ .cond = PTHREAD_COND_INITIALIZER,
+ .cond_mutex = PTHREAD_MUTEX_INITIALIZER,
};
static struct consumer_data ustconsumer64_data = {
.type = LTTNG_CONSUMER64_UST,
@@ -99,6 +103,8 @@ static struct consumer_data ustconsumer64_data = {
.cmd_sock = -1,
.pid_mutex = PTHREAD_MUTEX_INITIALIZER,
.lock = PTHREAD_MUTEX_INITIALIZER,
+ .cond = PTHREAD_COND_INITIALIZER,
+ .cond_mutex = PTHREAD_MUTEX_INITIALIZER,
};
static struct consumer_data ustconsumer32_data = {
.type = LTTNG_CONSUMER32_UST,
@@ -108,6 +114,8 @@ static struct consumer_data ustconsumer32_data = {
.cmd_sock = -1,
.pid_mutex = PTHREAD_MUTEX_INITIALIZER,
.lock = PTHREAD_MUTEX_INITIALIZER,
+ .cond = PTHREAD_COND_INITIALIZER,
+ .cond_mutex = PTHREAD_MUTEX_INITIALIZER,
};
/* Shared between threads */
@@ -789,6 +797,20 @@ error_poll_create:
}
/*
+ * Signal pthread condition of the consumer data that the thread.
+ */
+static void signal_consumer_condition(struct consumer_data *data, int state)
+{
+ pthread_mutex_lock(&data->cond_mutex);
+
+ /* Indicates that the thread is ready for action! */
+ data->consumer_thread_is_ready = state;
+ (void) pthread_cond_signal(&data->cond);
+
+ pthread_mutex_unlock(&data->cond_mutex);
+}
+
+/*
* This thread manage the consumer error sent back to the session daemon.
*/
static void *thread_manage_consumer(void *data)
@@ -886,13 +908,13 @@ restart:
consumer_data->cmd_sock =
lttcomm_connect_unix_sock(consumer_data->cmd_unix_sock_path);
if (consumer_data->cmd_sock < 0) {
- sem_post(&consumer_data->sem);
+ /* On error, signal condition and quit. */
+ signal_consumer_condition(consumer_data, -1);
PERROR("consumer connect");
goto error;
}
- /* Signal condition to tell that the kconsumerd is ready */
- sem_post(&consumer_data->sem);
- DBG("consumer command socket ready");
+ signal_consumer_condition(consumer_data, 1);
+ DBG("Consumer command socket ready");
} else {
ERR("consumer error when waiting for SOCK_READY : %s",
lttcomm_get_readable_code(-code));
@@ -1446,59 +1468,106 @@ error_create_poll:
*/
static int spawn_consumer_thread(struct consumer_data *consumer_data)
{
- int ret;
+ int ret, clock_ret;
struct timespec timeout;
- timeout.tv_sec = DEFAULT_SEM_WAIT_TIMEOUT;
- timeout.tv_nsec = 0;
+ /* Make sure we set the readiness flag to 0 because we are NOT ready */
+ consumer_data->consumer_thread_is_ready = 0;
- /* Setup semaphore */
- ret = sem_init(&consumer_data->sem, 0, 0);
- if (ret < 0) {
- PERROR("sem_init consumer semaphore");
+ /* Setup pthread condition */
+ ret = pthread_condattr_init(&consumer_data->condattr);
+ if (ret != 0) {
+ errno = ret;
+ PERROR("pthread_condattr_init consumer data");
+ goto error;
+ }
+
+ /*
+ * Set the monotonic clock in order to make sure we DO NOT jump in time
+ * between the clock_gettime() call and the timedwait call. See bug #324
+ * for a more details and how we noticed it.
+ */
+ ret = pthread_condattr_setclock(&consumer_data->condattr,
CLOCK_MONOTONIC);
+ if (ret != 0) {
+ errno = ret;
+ PERROR("pthread_condattr_setclock consumer data");
goto error;
}
- ret = pthread_create(&consumer_data->thread, NULL,
- thread_manage_consumer, consumer_data);
+ ret = pthread_cond_init(&consumer_data->cond, &consumer_data->condattr);
+ if (ret != 0) {
+ errno = ret;
+ PERROR("pthread_cond_init consumer data");
+ goto error;
+ }
+
+ ret = pthread_create(&consumer_data->thread, NULL,
thread_manage_consumer,
+ consumer_data);
if (ret != 0) {
PERROR("pthread_create consumer");
ret = -1;
goto error;
}
+ /* We are about to wait on a pthread condition */
+ pthread_mutex_lock(&consumer_data->cond_mutex);
+
/* Get time for sem_timedwait absolute timeout */
- ret = clock_gettime(CLOCK_REALTIME, &timeout);
- if (ret < 0) {
- PERROR("clock_gettime spawn consumer");
- /* Infinite wait for the kconsumerd thread to be ready */
- ret = sem_wait(&consumer_data->sem);
- } else {
- /* Normal timeout if the gettime was successful */
- timeout.tv_sec += DEFAULT_SEM_WAIT_TIMEOUT;
- ret = sem_timedwait(&consumer_data->sem, &timeout);
+ clock_ret = clock_gettime(CLOCK_MONOTONIC, &timeout);
+ /*
+ * Set the timeout for the condition timed wait even if the clock
gettime
+ * call fails since we might loop on that call and we want to avoid to
+ * incremente the timeout too many times.
+ */
+ timeout.tv_sec += DEFAULT_SEM_WAIT_TIMEOUT;
+
+ /* Make sure that ret is never set to ETIMEDOUT before reaching the
loop */
+ ret = 0;
+
+ /*
+ * Loop until the condition is reached or when a timeout is reached.
Note
+ * that the pthread_cond_timedwait(P) man page specifies that EINTR can
NOT
+ * be returned but the pthread_cond(3), from the glibc-doc, says that
it is
+ * possible. This loop does not take any chances and works with both of
+ * them.
+ */
+ while (!consumer_data->consumer_thread_is_ready && ret != ETIMEDOUT) {
+ if (clock_ret < 0) {
+ PERROR("clock_gettime spawn consumer");
+ /* Infinite wait for the consumerd thread to be ready */
+ ret = pthread_cond_wait(&consumer_data->cond,
+ &consumer_data->cond_mutex);
+ } else {
+ ret = pthread_cond_timedwait(&consumer_data->cond,
+ &consumer_data->cond_mutex, &timeout);
+ }
}
- if (ret < 0) {
- if (errno == ETIMEDOUT) {
+ /* Release the pthread condition */
+ pthread_mutex_unlock(&consumer_data->cond_mutex);
+
+ if (ret != 0) {
+ errno = ret;
+ if (ret == ETIMEDOUT) {
/*
* Call has timed out so we kill the kconsumerd_thread
and return
* an error.
*/
- ERR("The consumer thread was never ready. Killing it");
+ ERR("Condition timed out. The consumer thread was never
ready."
+ " Killing it");
ret = pthread_cancel(consumer_data->thread);
if (ret < 0) {
PERROR("pthread_cancel consumer thread");
}
} else {
- PERROR("semaphore wait failed consumer thread");
+ PERROR("pthread_cond_wait failed consumer thread");
}
goto error;
}
pthread_mutex_lock(&consumer_data->pid_mutex);
if (consumer_data->pid == 0) {
- ERR("Kconsumerd did not start");
+ ERR("Consumerd did not start");
pthread_mutex_unlock(&consumer_data->pid_mutex);
goto error;
}
--
1.7.10.4
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