libust ABI: export streams

[lttng-ust.git] / libust / lttng-ust-comm.c

diff --git a/libust/lttng-ust-comm.c b/libust/lttng-ust-comm.c
index a5f2b0b0069de494f0fb44dd14fdde78537002e6..d88c4afb2346c000dedd5a96c9fa5239f37bb265 100644 (file)
--- a/libust/lttng-ust-comm.c
+++ b/libust/lttng-ust-comm.c
@@ -119,6 +119,8 @@ struct sock_info local_apps = {
        .socket = -1,
 };
 
+static int wait_poll_fallback;
+
 extern void ltt_ring_buffer_client_overwrite_init(void);
 extern void ltt_ring_buffer_client_discard_init(void);
 extern void ltt_ring_buffer_metadata_client_init(void);
@@ -215,6 +217,9 @@ int handle_register_done(struct sock_info *sock_info)
        if (sock_info->constructor_sem_posted)
                return 0;
        sock_info->constructor_sem_posted = 1;
+       if (uatomic_read(&sem_count) <= 0) {
+               return 0;
+       }
        ret = uatomic_add_return(&sem_count, -1);
        if (ret == 0) {
                ret = sem_post(&constructor_wait);
@@ -277,8 +282,33 @@ end:
        } else {
                lur.ret_code = LTTCOMM_SESSION_FAIL;
        }
+       if (lum->cmd == LTTNG_UST_STREAM) {
+               /*
+                * Special-case reply to send stream info.
+                * Use lum.u output.
+                */
+               lur.u.stream.memory_map_size = lum->u.stream.memory_map_size;
+       }
        ret = send_reply(sock, &lur);
 
+       if (lum->cmd == LTTNG_UST_STREAM && ret >= 0) {
+               /* we also need to send the file descriptors. */
+               ret = lttcomm_send_fds_unix_sock(sock,
+                       &lum->u.stream.shm_fd, &lum->u.stream.shm_fd,
+                       1, sizeof(int));
+               if (ret < 0) {
+                       perror("send shm_fd");
+                       goto error;
+               }
+               ret = lttcomm_send_fds_unix_sock(sock,
+                       &lum->u.stream.wait_fd, &lum->u.stream.wait_fd,
+                       1, sizeof(int));
+               if (ret < 0) {
+                       perror("send wait_fd");
+                       goto error;
+               }
+       }
+error:
        ust_unlock();
        return ret;
 }
@@ -485,6 +515,9 @@ void wait_for_sessiond(struct sock_info *sock_info)
        if (lttng_ust_comm_should_quit) {
                goto quit;
        }
+       if (wait_poll_fallback) {
+               goto error;
+       }
        if (!sock_info->wait_shm_mmap) {
                sock_info->wait_shm_mmap = get_map_shm(sock_info);
                if (!sock_info->wait_shm_mmap)
@@ -497,13 +530,17 @@ void wait_for_sessiond(struct sock_info *sock_info)
        if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) {
                ret = futex_async((int32_t *) sock_info->wait_shm_mmap,
                        FUTEX_WAIT, 0, NULL, NULL, 0);
-               /*
-                * FIXME: Currently, futexes on read-only shm seems to
-                * EFAULT.
-                */
                if (ret < 0) {
+                       if (errno == EFAULT) {
+                               wait_poll_fallback = 1;
+                               ERR(
+"Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
+"do not support FUTEX_WAKE on read-only memory mappings correctly. "
+"Please upgrade your kernel "
+"(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
+"mainline). LTTng-UST will use polling mode fallback.");
+                       }
                        PERROR("futex");
-                       sleep(5);
                }
        }
        return;
@@ -514,8 +551,6 @@ quit:
 
 error:
        ust_unlock();
-       /* Error handling: fallback on a 5 seconds sleep. */
-       sleep(5);
        return;
 }
 
@@ -530,10 +565,25 @@ static
 void *ust_listener_thread(void *arg)
 {
        struct sock_info *sock_info = arg;
-       int sock, ret;
+       int sock, ret, prev_connect_failed = 0, has_waited = 0;
 
        /* Restart trying to connect to the session daemon */
 restart:
+       if (prev_connect_failed) {
+               /* Wait for sessiond availability with pipe */
+               wait_for_sessiond(sock_info);
+               if (has_waited) {
+                       has_waited = 0;
+                       /*
+                        * Sleep for 5 seconds before retrying after a
+                        * sequence of failure / wait / failure. This
+                        * deals with a killed or broken session daemon.
+                        */
+                       sleep(5);
+               }
+               has_waited = 1;
+               prev_connect_failed = 0;
+       }
        ust_lock();
 
        if (lttng_ust_comm_should_quit) {
@@ -553,6 +603,7 @@ restart:
        ret = lttcomm_connect_unix_sock(sock_info->sock_path);
        if (ret < 0) {
                ERR("Error connecting to %s apps socket", sock_info->name);
+               prev_connect_failed = 1;
                /*
                 * If we cannot find the sessiond daemon, don't delay
                 * constructor execution.
@@ -560,9 +611,6 @@ restart:
                ret = handle_register_done(sock_info);
                assert(!ret);
                ust_unlock();
-
-               /* Wait for sessiond availability with pipe */
-               wait_for_sessiond(sock_info);
                goto restart;
        }
 
@@ -585,6 +633,7 @@ restart:
        ret = register_app_to_sessiond(sock);
        if (ret < 0) {
                ERR("Error registering to %s apps socket", sock_info->name);
+               prev_connect_failed = 1;
                /*
                 * If we cannot register to the sessiond daemon, don't
                 * delay constructor execution.
@@ -592,7 +641,6 @@ restart:
                ret = handle_register_done(sock_info);
                assert(!ret);
                ust_unlock();
-               wait_for_sessiond(sock_info);
                goto restart;
        }
        ust_unlock();