Remove the timeout on poll

Use a shared pipe to wake the poll thread when new fds arrive.

Signed-off-by: Julien Desfossez <julien.desfossez@polymtl.ca>

diff --git a/kconsumerd/kconsumerd.c b/kconsumerd/kconsumerd.c
index 66f3877d020cddae531fd123fc7df4ab31757e18..fcd4101a62d0bdbdff1b7ffcd34a86365324afbf 100644 (file)
--- a/kconsumerd/kconsumerd.c
+++ b/kconsumerd/kconsumerd.c
@@ -61,6 +61,9 @@ static pthread_t threads[2];
 /* communication with splice */
 static int thread_pipe[2];
 
+/* pipe to wake the poll thread when necessary */
+static int poll_pipe[2];
+
 /* socket to communicate errors with sessiond */
 static int error_socket = -1;
 
@@ -404,7 +407,7 @@ static int consumerd_recv_fd(int sfd, int size,
 {
        struct msghdr msg;
        struct iovec iov[1];
-       int ret, i;
+       int ret, i, tmp2;
        struct cmsghdr *cmsg;
        int nb_fd;
        char tmp[CMSG_SPACE(size)];
@@ -465,7 +468,8 @@ static int consumerd_recv_fd(int sfd, int size,
                }
                /* flag to tell the polling thread to update its fd array */
                update_fd_array = 1;
-               send_error(KCONSUMERD_SUCCESS_RECV_FD);
+               /* signal the poll thread */
+               tmp2 = write(poll_pipe[1], "4", 1);
        } else {
                ERR("Didn't received any fd");
                send_error(KCONSUMERD_ERROR_RECV_FD);
@@ -561,13 +565,15 @@ static int update_poll_array(struct pollfd **pollfd,
                *local_kconsumerd_fd = NULL;
        }
 
-       *pollfd = malloc(fds_count * sizeof(struct pollfd));
+       /* allocate for all fds + 1 for the poll_pipe */
+       *pollfd = malloc((fds_count + 1) * sizeof(struct pollfd));
        if (*pollfd == NULL) {
                perror("pollfd malloc");
                goto error_mem;
        }
 
-       *local_kconsumerd_fd = malloc(fds_count * sizeof(struct ltt_kconsumerd_fd));
+       /* allocate for all fds + 1 for the poll_pipe */
+       *local_kconsumerd_fd = malloc((fds_count + 1) * sizeof(struct ltt_kconsumerd_fd));
        if (*local_kconsumerd_fd == NULL) {
                perror("local_kconsumerd_fd malloc");
                goto error_mem;
@@ -588,6 +594,13 @@ static int update_poll_array(struct pollfd **pollfd,
                        del_fd(iter);
                }
        }
+       /*
+        * insert the poll_pipe at the end of the array and don't increment i
+        * so nb_fd is the number of real FD
+        */
+       (*pollfd)[i].fd = poll_pipe[0];
+       (*pollfd)[i].events = POLLIN;
+
        update_fd_array = 0;
        pthread_mutex_unlock(&kconsumerd_lock_fds);
        return i;
@@ -610,6 +623,8 @@ static void *thread_poll_fds(void *data)
        struct ltt_kconsumerd_fd **local_kconsumerd_fd = NULL;
        /* local view of fds_count */
        int nb_fd = 0;
+       char tmp;
+       int tmp2;
 
        ret = pipe(thread_pipe);
        if (ret < 0) {
@@ -638,8 +653,8 @@ static void *thread_poll_fds(void *data)
                }
 
                /* poll on the array of fds */
-               DBG("polling on %d fd", nb_fd);
-               num_rdy = poll(pollfd, nb_fd, POLL_TIMEOUT);
+               DBG("polling on %d fd", nb_fd + 1);
+               num_rdy = poll(pollfd, nb_fd + 1, -1);
                DBG("poll num_rdy : %d", num_rdy);
                if (num_rdy == -1) {
                        perror("Poll error");
@@ -647,6 +662,16 @@ static void *thread_poll_fds(void *data)
                        goto end;
                }
 
+               /*
+                * if only the poll_pipe triggered poll to return just return to the
+                * beginning of the loop to update the array
+                */
+               if (num_rdy == 1 && pollfd[nb_fd].revents == POLLIN) {
+                       DBG("poll_pipe wake up");
+                       tmp2 = read(poll_pipe[0], &tmp, 1);
+                       continue;
+               }
+
                /* Take care of high priority channels first. */
                for (i = 0; i < nb_fd; i++) {
                        switch(pollfd[i].revents) {
@@ -830,6 +855,13 @@ int main(int argc, char **argv)
                goto error;
        }
 
+       /* create the pipe to wake to polling thread when needed */
+       ret = pipe(poll_pipe);
+       if (ret < 0) {
+               perror("Error creating poll pipe");
+               goto end;
+       }
+
        /* Connect to the socket created by ltt-sessiond to report errors */
        DBG("Connecting to error socket %s", error_sock_path);
        error_socket = lttcomm_connect_unix_sock(error_sock_path);

diff --git a/kconsumerd/kconsumerd.h b/kconsumerd/kconsumerd.h
index f5ec288bc62a9fd177d433a19a1453c90579a52b..6c78663f5e67900cfbbed0129a8f75c4d65929d1 100644 (file)
--- a/kconsumerd/kconsumerd.h
+++ b/kconsumerd/kconsumerd.h
@@ -19,9 +19,6 @@
 #ifndef _LTT_KCONSUMERD_H
 #define _LTT_KCONSUMERD_H
 
-/* timeout of 1s on poll to ensure the fd list is updated when needed */
-#define POLL_TIMEOUT 1000
-
 struct ltt_kconsumerd_fd_list {
        struct cds_list_head head;
 };