Prevent channel buffer allocation larger than memory

[lttng-tools.git] / src / lib / lttng-ctl / lttng-ctl.c

diff --git a/src/lib/lttng-ctl/lttng-ctl.c b/src/lib/lttng-ctl/lttng-ctl.c
index b57be223a73afce55723c858c66a5aedfa245b24..165fef4dc5c412392fe49daec62be947d4de3853 100644 (file)
--- a/src/lib/lttng-ctl/lttng-ctl.c
+++ b/src/lib/lttng-ctl/lttng-ctl.c
@@ -287,6 +287,50 @@ end:
        return ret;
 }
 
+static int check_enough_available_memory(size_t num_bytes_requested_per_cpu)
+{
+       int ret;
+       long num_cpu;
+       size_t best_mem_info;
+       size_t num_bytes_requested_total;
+
+       /*
+        * Get the number of CPU currently online to compute the amount of
+        * memory needed to create a buffer for every CPU.
+        */
+       num_cpu = sysconf(_SC_NPROCESSORS_ONLN);
+       if (num_cpu == -1) {
+               goto error;
+       }
+
+       num_bytes_requested_total = num_bytes_requested_per_cpu * num_cpu;
+
+       /*
+        * Try to get the `MemAvail` field of `/proc/meminfo`. This is the most
+        * reliable estimate we can get but it is only exposed by the kernel
+        * since 3.14. (See Linux kernel commit:
+        * 34e431b0ae398fc54ea69ff85ec700722c9da773)
+        */
+       ret = utils_get_memory_available(&best_mem_info);
+       if (ret >= 0) {
+               goto success;
+       }
+
+       /*
+        * As a backup plan, use `MemTotal` field of `/proc/meminfo`. This
+        * is a sanity check for obvious user error.
+        */
+       ret = utils_get_memory_total(&best_mem_info);
+       if (ret >= 0) {
+               goto success;
+       }
+
+error:
+       return -1;
+success:
+       return best_mem_info >= num_bytes_requested_total;
+}
+
 /*
  * Try connect to session daemon with sock_path.
  *
@@ -1475,6 +1519,7 @@ int lttng_enable_channel(struct lttng_handle *handle,
                struct lttng_channel *in_chan)
 {
        struct lttcomm_session_msg lsm;
+       size_t total_buffer_size_needed_per_cpu = 0;
 
        /* NULL arguments are forbidden. No default values. */
        if (handle == NULL || in_chan == NULL) {
@@ -1510,6 +1555,16 @@ int lttng_enable_channel(struct lttng_handle *handle,
                memcpy(&lsm.u.channel.extended, extended, sizeof(*extended));
        }
 
+       /*
+        * Verify that the amount of memory required to create the requested
+        * buffer is available on the system at the moment.
+        */
+       total_buffer_size_needed_per_cpu = lsm.u.channel.chan.attr.num_subbuf *
+               lsm.u.channel.chan.attr.subbuf_size;
+       if (!check_enough_available_memory(total_buffer_size_needed_per_cpu)) {
+               return -LTTNG_ERR_NOMEM;
+       }
+
        lsm.cmd_type = LTTNG_ENABLE_CHANNEL;
        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);