X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=liblttng-ust%2Flttng-ust-comm.c;h=43914465d30a64045c448574290866f577715f30;hb=b2292d8567372f5bbadaeb0cd7b26e6fc4cd1b56;hp=0cf5ecd9687536be5fc7794c4bfeb28ed135a11f;hpb=35ac38cb4cc188253c600766882b7a833f5a81ee;p=lttng-ust.git

diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index 0cf5ecd9..43914465 100644
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -27,6 +27,7 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <dlfcn.h>
 #include <fcntl.h>
 #include <unistd.h>
 #include <errno.h>
@@ -59,6 +60,9 @@
 #include "../libringbuffer/getcpu.h"
 #include "getenv.h"
 
+/* Concatenate lttng ust shared library name with its major version number. */
+#define LTTNG_UST_LIB_SO_NAME "liblttng-ust.so." LTTNG_UST_LIBRARY_VERSION_MAJOR
+
 /*
  * Has lttng ust comm constructor been called ?
  */
@@ -1685,6 +1689,7 @@ void __attribute__((constructor)) lttng_ust_init(void)
 	pthread_attr_t thread_attr;
 	int timeout_mode;
 	int ret;
+	void *handle;
 
 	if (uatomic_xchg(&initialized, 1) == 1)
 		return;
@@ -1698,6 +1703,26 @@ void __attribute__((constructor)) lttng_ust_init(void)
 
 	lttng_ust_loaded = 1;
 
+	/*
+	 * We need to ensure that the liblttng-ust library is not unloaded to avoid
+	 * the unloading of code used by the ust_listener_threads as we can not
+	 * reliably know when they exited. To do that, manually load
+	 * liblttng-ust.so to increment the dynamic loader's internal refcount for
+	 * this library so it never becomes zero, thus never gets unloaded from the
+	 * address space of the process. Since we are already running in the
+	 * constructor of the LTTNG_UST_LIB_SO_NAME library, calling dlopen will
+	 * simply increment the refcount and no additionnal work is needed by the
+	 * dynamic loader as the shared library is already loaded in the address
+	 * space. As a safe guard, we use the RTLD_NODELETE flag to prevent
+	 * unloading of the UST library if its refcount becomes zero (which should
+	 * never happen). Do the return value check but discard the handle at the
+	 * end of the function as it's not needed.
+	 */
+	handle = dlopen(LTTNG_UST_LIB_SO_NAME, RTLD_LAZY | RTLD_NODELETE);
+	if (!handle) {
+		ERR("dlopen of liblttng-ust shared library (%s).", LTTNG_UST_LIB_SO_NAME);
+	}
+
 	/*
 	 * We want precise control over the order in which we construct
 	 * our sub-libraries vs starting to receive commands from