tracepoints: increase dlopen failure message level from debug to critical

Print the failure message associated with failing to find
lttng-ust-tracepoint.so as a "Critical: " message, because when this
situation occurs, it indeeds makes part of that application's
instrumentation invisible to the tracer.

Similarly to debug message, this critical message is only shown if
LTTNG_UST_DEBUG is defined for the compile unit or if the
LTTNG_UST_DEBUG environment variable is set.

In addition however, if LTTNG_UST_ABORT_ON_CRITICAL is defined at
compile-time, or if the application is run with the
LTTNG_UST_ABORT_ON_CRITICAL environment variable set, the construction
will call abort() on failure to find lttng-ust-tracepoint.so.

This should make it easier for end-users to identify deployment issues
which prevent the lttng-ust tracer from being aware of application
tracepoints.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I2ddcfd593eae699a2c18ef85049ac2239dd41411

diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h
index 17fa2a0c68ef884857cc6dfa5066172e425d2b0d..b10c514e21c86fae23f8f91b37d14adbb66b1bf7 100644 (file)
--- a/include/lttng/tracepoint.h
+++ b/include/lttng/tracepoint.h
@@ -413,20 +413,35 @@ bool lttng_ust_tracepoint_logging_debug_enabled(void)
 }
 #endif /* #ifdef LTTNG_UST_DEBUG */
 
+#ifdef LTTNG_UST_ABORT_ON_CRITICAL
+static inline
+bool lttng_ust_tracepoint_logging_abort_on_critical_enabled(void)
+{
+       return true;
+}
+#else /* #ifdef LTTNG_UST_ABORT_ON_CRITICAL */
+static inline
+bool lttng_ust_tracepoint_logging_abort_on_critical_enabled(void)
+{
+       return getenv("LTTNG_UST_ABORT_ON_CRITICAL");
+}
+#endif
+
 #define LTTNG_UST_TRACEPOINT_THIS_IP           \
        ({ __label__ here; here: &&here; })
 
 static void
 lttng_ust_tracepoints_print_disabled_message(void)
 {
-       if (!lttng_ust_tracepoint_logging_debug_enabled())
-               return;
-       fprintf(stderr, "lttng-ust-tracepoint [%ld]: dlopen() failed to find '%s', tracepoints in this binary won't be registered. "
-               "(at addr=%p in %s() at " __FILE__ ":" lttng_ust_stringify(__LINE__) ")\n",
-               (long) getpid(),
-               LTTNG_UST_TRACEPOINT_LIB_SONAME,
-               LTTNG_UST_TRACEPOINT_THIS_IP,
-               __func__);
+       if (lttng_ust_tracepoint_logging_debug_enabled())
+               fprintf(stderr, "lttng-ust-tracepoint [%ld]: Critical: dlopen() failed to find '%s', tracepoints in this binary won't be registered. "
+                       "(at addr=%p in %s() at " __FILE__ ":" lttng_ust_stringify(__LINE__) ")\n",
+                       (long) getpid(),
+                       LTTNG_UST_TRACEPOINT_LIB_SONAME,
+                       LTTNG_UST_TRACEPOINT_THIS_IP,
+                       __func__);
+       if (lttng_ust_tracepoint_logging_abort_on_critical_enabled())
+               abort();
 }
 
 static void