ust consumer: close shm fd after mapping it

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/liblttng-ust-ctl/ustctl.c b/liblttng-ust-ctl/ustctl.c
index f7e13a1a06e8618823899e8a49286278d8f4ce5a..8dce787897a3424fe9c75c465533c8bc192a1039 100644 (file)
--- a/liblttng-ust-ctl/ustctl.c
+++ b/liblttng-ust-ctl/ustctl.c
@@ -507,12 +507,24 @@ struct lttng_ust_shm_handle *ustctl_map_channel(struct lttng_ust_object_data *ch
                return NULL;
        }
        /*
-        * Set to -1 because the lttng_ust_shm_handle destruction will take care
-        * of closing shm_fd and wait_fd.
+        * Set to -1, and then close the shm fd, and set the handle shm
+        * fd to -1 too. We don't need the shm fds after they have been
+        * mapped.
+        * The wait_fd is set to -1 in chan_data because it is now owned
+        * by the handle.
         */
        chan_data->shm_fd = -1;
        chan_data->wait_fd = -1;
 
+       /* chan is object 0. This is hardcoded. */
+       if (handle->table->objects[0].shm_fd >= 0) {
+               ret = close(handle->table->objects[0].shm_fd);
+               if (ret) {
+                       perror("Error closing shm_fd");
+               }
+               handle->table->objects[0].shm_fd = -1;
+       }
+
        /*
         * TODO: add consistency checks to be resilient if the
         * application try to feed us with incoherent channel structure
@@ -596,6 +608,9 @@ void ustctl_unmap_channel(struct lttng_ust_shm_handle *handle)
        channel_destroy(chan, handle, 1);
 }
 
+/*
+ * ustctl closes the shm_fd fds after mapping it.
+ */
 struct lttng_ust_lib_ring_buffer *ustctl_open_stream_read(struct lttng_ust_shm_handle *handle,
        int cpu)
 {
@@ -612,6 +627,16 @@ struct lttng_ust_lib_ring_buffer *ustctl_open_stream_read(struct lttng_ust_shm_h
        ret = lib_ring_buffer_open_read(buf, handle, 1);
        if (ret)
                return NULL;
+       /*
+        * We can close shm_fd early, right after is has been mapped.
+        */
+       if (*shm_fd >= 0) {
+               ret = close(*shm_fd);
+               if (ret) {
+                       perror("Error closing shm_fd");
+               }
+               *shm_fd = -1;
+       }
        return buf;
 }