[lttng-dev] [PATCH] Set appropriate thread names for processes loading UST lib

[André Goddard Rosa]

When a process loads UST library, set appropriate individual threads names
so that it becomes easier to distinguish between its own threads from those
coming from UST.

That makes for easier understanding of profiling data where cycles are
accounted to individual threads, allowing to distinguish the originating
libraries and functions for the gathered profiling data.

Caveat: not tested on __FreeBSD__ environment. Does somebody already has
FreeBSD environment setup to try?

Signed-off-by: André Goddard Rosa <andre.goddard at gmail.com>

diff --git a/liblttng-ust/compat.h b/liblttng-ust/compat.h
index 43b2223..657703e 100644
--- a/liblttng-ust/compat.h
+++ b/liblttng-ust/compat.h
@@ -20,7 +20,7 @@
  */
 
 /*
- * lttng_ust_getprocname.
+ * lttng_ust_getprocname, lttng_ust_setprocname.
  */
 #ifdef __linux__
 
@@ -34,9 +34,16 @@ void lttng_ust_getprocname(char *name)
 	(void) prctl(PR_GET_NAME, (unsigned long) name, 0, 0, 0);
 }
 
+static inline
+void lttng_ust_setprocname(char *name)
+{
+	(void) prctl(PR_SET_NAME, (unsigned long) name, 0, 0, 0);
+}
+
 #elif defined(__FreeBSD__)
 #include <stdlib.h>
 #include <string.h>
+#include <pthread.h>
 
 /*
  * Limit imposed by Linux UST-sessiond ABI.
@@ -59,6 +66,12 @@ void lttng_ust_getprocname(char *name)
 		strncpy(name, bsd_name, LTTNG_UST_PROCNAME_LEN - 1);
 }
 
+static inline
+void lttng_ust_setprocname(char *name)
+{
+	(void) pthread_set_name_np(pthread_self(), name);
+}
+
 #endif
 
 #include <errno.h>
diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index 378ca21..256752b 100644
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -1173,6 +1173,8 @@ void *ust_listener_thread(void *arg)
 	int sock, ret, prev_connect_failed = 0, has_waited = 0;
 	long timeout;
 
+	lttng_ust_setprocname("UST Listener");
+
 	/* Restart trying to connect to the session daemon */
 restart:
 	if (prev_connect_failed) {
diff --git a/libringbuffer/ring_buffer_frontend.c b/libringbuffer/ring_buffer_frontend.c
index aeb7f7d..675abb6 100644
--- a/libringbuffer/ring_buffer_frontend.c
+++ b/libringbuffer/ring_buffer_frontend.c
@@ -398,6 +398,8 @@ void *sig_thread(void *arg)
 	siginfo_t info;
 	int signr;
 
+	lttng_ust_setprocname("UST Sig");
+
 	/* Only self thread will receive signal mask. */
 	rb_setmask(&mask);
 	CMM_STORE_SHARED(timer_signal.tid, pthread_self());
-- 
2.3.0.rc1