[ltt-dev] [LTTNG-TOOLS PATCH 2/2] Callbacks on receive and update FD
Mathieu Desnoyers
mathieu.desnoyers at efficios.com
Tue Aug 16 14:20:43 EDT 2011
* Julien Desfossez (julien.desfossez at polymtl.ca) wrote:
[...]
> /* function to call when data is available on a buffer */
> int (*on_buffer_ready)(struct lttng_kconsumerd_fd *kconsumerd_fd);
> + /*
> + * function to call when we receive a new fd, it receives a newly allocated
> + * kconsumerd_fd, if it returns the FD (as seen by the sessiond daemon :
> + * sessiond_fd), the FD will be handled by the lib in the local FD list,
> + * otherwise we assume the external consumer is taking care of it.
> + */
Rather than returning the "same" fd, which is a little weird, we could
just return:
- > 0 (success, FD is kept by application)
- == 0 (success, FD is left to library)
- < 0 (error)
- also add an argument int *fd to the function though which is would
be returned. I prefer not to use the return value for this, because
theoretically the fd number "0" could be used as a valid fd number if
the application close stdout.
Thanks,
Mathieu
> + int (*on_recv_fd)(struct lttng_kconsumerd_fd *kconsumerd_fd);
> + /*
> + * function to call when a FD is getting updated by the session daemon,
> + * this function receives the FD as seen by the session daemon
> + * (sessiond_fd) and the new state, if it returns the fd, it will be
> + * handled locally by the lib, otherwise we assume the consumer is taking
> + * care of it.
> + */
> + int (*on_update_fd)(int sessiond_fd, uint32_t state);
> /* socket to communicate errors with sessiond */
> int kconsumerd_error_socket;
> /* socket to exchange commands with sessiond */
> @@ -98,15 +113,15 @@ struct lttng_kconsumerd_local_data {
> * - create the should_quit pipe (for signal handler)
> * - create the thread pipe (for splice)
> *
> - * Takes a function pointer as argument, this function is called when data is
> - * available on a buffer. This function is responsible to do the
> - * kernctl_get_next_subbuf, read the data with mmap or splice depending on the
> - * buffer configuration and then kernctl_put_next_subbuf at the end.
> + * Takes the function pointers to the on_buffer_ready, on_recv_fd, and
> + * on_update_fd callbacks.
> *
> * Returns a pointer to the new context or NULL on error.
> */
> extern struct lttng_kconsumerd_local_data *lttng_kconsumerd_create(
> - int (*buffer_ready)(struct lttng_kconsumerd_fd *kconsumerd_fd));
> + int (*buffer_ready)(struct lttng_kconsumerd_fd *kconsumerd_fd),
> + int (*recv_fd)(struct lttng_kconsumerd_fd *kconsumerd_fd),
> + int (*update_fd)(int sessiond_fd, uint32_t state));
>
> /*
> * Close all fds associated with the instance and free the context.
> diff --git a/liblttngkconsumerd/lttngkconsumerd.c b/liblttngkconsumerd/lttngkconsumerd.c
> index d36da9b..ed7951b 100644
> --- a/liblttngkconsumerd/lttngkconsumerd.c
> +++ b/liblttngkconsumerd/lttngkconsumerd.c
> @@ -125,22 +125,21 @@ static void kconsumerd_del_fd(struct lttng_kconsumerd_fd *lcf)
> }
>
> /*
> - * Add a fd to the global list protected by a mutex.
> + * Create a struct lttcomm_kconsumerd_msg from the
> + * information received on the receiving socket
> */
> -static int kconsumerd_add_fd(struct lttcomm_kconsumerd_msg *buf,
> +struct lttng_kconsumerd_fd *kconsumerd_allocate_fd(
> + struct lttcomm_kconsumerd_msg *buf,
> int consumerd_fd)
> {
> struct lttng_kconsumerd_fd *tmp_fd;
> - int ret = 0;
>
> - pthread_mutex_lock(&kconsumerd_data.lock);
> - /* Check if already exist */
> - ret = kconsumerd_find_session_fd(buf->fd);
> - if (ret == 1) {
> + tmp_fd = malloc(sizeof(struct lttng_kconsumerd_fd));
> + if (tmp_fd == NULL) {
> + perror("malloc struct lttng_kconsumerd_fd");
> goto end;
> }
>
> - tmp_fd = malloc(sizeof(struct lttng_kconsumerd_fd));
> tmp_fd->sessiond_fd = buf->fd;
> tmp_fd->consumerd_fd = consumerd_fd;
> tmp_fd->state = buf->state;
> @@ -152,42 +151,31 @@ static int kconsumerd_add_fd(struct lttcomm_kconsumerd_msg *buf,
> tmp_fd->output = buf->output;
> strncpy(tmp_fd->path_name, buf->path_name, PATH_MAX);
> tmp_fd->path_name[PATH_MAX - 1] = '\0';
> + DBG("Allocated %s (sessiond_fd %d, consumerd_fd %d, out_fd %d)",
> + tmp_fd->path_name, tmp_fd->sessiond_fd,
> + tmp_fd->consumerd_fd, tmp_fd->out_fd);
>
> - /* Opening the tracefile in write mode */
> - if (tmp_fd->path_name != NULL) {
> - ret = open(tmp_fd->path_name,
> - O_WRONLY|O_CREAT|O_TRUNC, S_IRWXU|S_IRWXG|S_IRWXO);
> - if (ret < 0) {
> - ERR("Opening %s", tmp_fd->path_name);
> - perror("open");
> - goto end;
> - }
> - tmp_fd->out_fd = ret;
> - DBG("Adding %s (%d, %d, %d)", tmp_fd->path_name,
> - tmp_fd->sessiond_fd, tmp_fd->consumerd_fd, tmp_fd->out_fd);
> - }
> +end:
> + return tmp_fd;
> +}
>
> - if (tmp_fd->output == LTTNG_EVENT_MMAP) {
> - /* get the len of the mmap region */
> - ret = kernctl_get_mmap_len(tmp_fd->consumerd_fd, &tmp_fd->mmap_len);
> - if (ret != 0) {
> - ret = errno;
> - perror("kernctl_get_mmap_len");
> - goto end;
> - }
> +/*
> + * Add a fd to the global list protected by a mutex.
> + */
> +static int kconsumerd_add_fd(struct lttng_kconsumerd_fd *tmp_fd)
> +{
> + int ret;
>
> - tmp_fd->mmap_base = mmap(NULL, tmp_fd->mmap_len,
> - PROT_READ, MAP_PRIVATE, tmp_fd->consumerd_fd, 0);
> - if (tmp_fd->mmap_base == MAP_FAILED) {
> - perror("Error mmaping");
> - ret = -1;
> - goto end;
> - }
> + pthread_mutex_lock(&kconsumerd_data.lock);
> + /* Check if already exist */
> + ret = kconsumerd_find_session_fd(tmp_fd->sessiond_fd);
> + if (ret == 1) {
> + goto end;
> }
> -
> cds_list_add(&tmp_fd->list, &kconsumerd_data.fd_list.head);
> kconsumerd_data.fds_count++;
> kconsumerd_data.need_update = 1;
> +
> end:
> pthread_mutex_unlock(&kconsumerd_data.lock);
> return ret;
> @@ -263,6 +251,7 @@ static int kconsumerd_consumerd_recv_fd(
> int nb_fd;
> char recv_fd[CMSG_SPACE(sizeof(int))];
> struct lttcomm_kconsumerd_msg lkm;
> + struct lttng_kconsumerd_fd *new_fd;
>
> /* the number of fds we are about to receive */
> nb_fd = size / sizeof(struct lttcomm_kconsumerd_msg);
> @@ -313,14 +302,40 @@ static int kconsumerd_consumerd_recv_fd(
> DBG("kconsumerd_add_fd %s (%d)", lkm.path_name,
> ((int *) CMSG_DATA(cmsg))[0]);
>
> - ret = kconsumerd_add_fd(&lkm, ((int *) CMSG_DATA(cmsg))[0]);
> - if (ret < 0) {
> + new_fd = kconsumerd_allocate_fd(&lkm, ((int *) CMSG_DATA(cmsg))[0]);
> + if (new_fd == NULL) {
> lttng_kconsumerd_send_error(ctx, KCONSUMERD_OUTFD_ERROR);
> goto end;
> }
> +
> + if (ctx->on_recv_fd != NULL) {
> + ret = ctx->on_recv_fd(new_fd);
> + /*
> + * if we receive the FD back, we insert it in the local
> + * FD list, otherwise we assume it is handled by the
> + * external consumer.
> + */
> + if (ret == new_fd->sessiond_fd) {
> + kconsumerd_add_fd(new_fd);
> + }
> + } else {
> + kconsumerd_add_fd(new_fd);
> + }
> break;
> case UPDATE_STREAM:
> - kconsumerd_change_fd_state(lkm.fd, lkm.state);
> + if (ctx->on_update_fd != NULL) {
> + ret = ctx->on_update_fd(lkm.fd, lkm.state);
> + /*
> + * if we receive the FD back, we have to handle it locally,
> + * otherwise we assume the external consumer is taking care
> + * of it.
> + */
> + if (ret == lkm.fd) {
> + kconsumerd_change_fd_state(lkm.fd, lkm.state);
> + }
> + } else {
> + kconsumerd_change_fd_state(lkm.fd, lkm.state);
> + }
> break;
> default:
> break;
> @@ -756,7 +771,9 @@ end:
> * Returns a pointer to the new context or NULL on error.
> */
> struct lttng_kconsumerd_local_data *lttng_kconsumerd_create(
> - int (*buffer_ready)(struct lttng_kconsumerd_fd *kconsumerd_fd))
> + int (*buffer_ready)(struct lttng_kconsumerd_fd *kconsumerd_fd),
> + int (*recv_fd)(struct lttng_kconsumerd_fd *kconsumerd_fd),
> + int (*update_fd)(int sessiond_fd, uint32_t state))
> {
> int ret;
> struct lttng_kconsumerd_local_data *ctx;
> @@ -767,7 +784,10 @@ struct lttng_kconsumerd_local_data *lttng_kconsumerd_create(
> goto end;
> }
>
> + /* assign the callbacks */
> ctx->on_buffer_ready = buffer_ready;
> + ctx->on_recv_fd = recv_fd;
> + ctx->on_update_fd = update_fd;
>
> ret = pipe(ctx->kconsumerd_poll_pipe);
> if (ret < 0) {
> diff --git a/ltt-kconsumerd/ltt-kconsumerd.c b/ltt-kconsumerd/ltt-kconsumerd.c
> index cd4b00e..f2bb211 100644
> --- a/ltt-kconsumerd/ltt-kconsumerd.c
> +++ b/ltt-kconsumerd/ltt-kconsumerd.c
> @@ -271,6 +271,47 @@ end:
> return ret;
> }
>
> +static int on_recv_fd(struct lttng_kconsumerd_fd *kconsumerd_fd)
> +{
> + int ret;
> +
> + /* Opening the tracefile in write mode */
> + if (kconsumerd_fd->path_name != NULL) {
> + ret = open(kconsumerd_fd->path_name,
> + O_WRONLY|O_CREAT|O_TRUNC, S_IRWXU|S_IRWXG|S_IRWXO);
> + if (ret < 0) {
> + ERR("Opening %s", kconsumerd_fd->path_name);
> + perror("open");
> + goto error;
> + }
> + kconsumerd_fd->out_fd = ret;
> + }
> +
> + if (kconsumerd_fd->output == LTTNG_EVENT_MMAP) {
> + /* get the len of the mmap region */
> + ret = kernctl_get_mmap_len(kconsumerd_fd->consumerd_fd, &kconsumerd_fd->mmap_len);
> + if (ret != 0) {
> + ret = errno;
> + perror("kernctl_get_mmap_len");
> + goto error;
> + }
> +
> + kconsumerd_fd->mmap_base = mmap(NULL, kconsumerd_fd->mmap_len,
> + PROT_READ, MAP_PRIVATE, kconsumerd_fd->consumerd_fd, 0);
> + if (kconsumerd_fd->mmap_base == MAP_FAILED) {
> + perror("Error mmaping");
> + ret = -1;
> + goto error;
> + }
> + }
> +
> + /* we return the FD back to the lib to let it handle the FD internally */
> + return kconsumerd_fd->sessiond_fd;
> +
> +error:
> + return ret;
> +}
> +
> /*
> * main
> */
> @@ -297,8 +338,8 @@ int main(int argc, char **argv)
> snprintf(command_sock_path, PATH_MAX,
> KCONSUMERD_CMD_SOCK_PATH);
> }
> - /* create the pipe to wake to receiving thread when needed */
> - ctx = lttng_kconsumerd_create(read_subbuffer);
> + /* create the consumer instance with and assign the callbacks */
> + ctx = lttng_kconsumerd_create(read_subbuffer, on_recv_fd, NULL);
> if (ctx == NULL) {
> goto error;
> }
> --
> 1.7.4.1
>
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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