Detect pthread_setname_np at configure time

Warn if no way of setting thread name is available.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

configure

@@ -2696,6 +2696,24 @@ if test "$mingw32" != yes -a "$pthread" = no; then
       "Make sure to have the pthread libs and headers installed."
 fi
 
+# check for pthread_setname_np
+pthread_setname_np=no
+cat > $TMPC << EOF
+#include <pthread.h>
+
+static void *f(void *p) { return NULL; }
+int main(void)
+{
+    pthread_t thread;
+    pthread_create(&thread, 0, f, 0);
+    pthread_setname_np(thread, "QEMU");
+    return 0;
+}
+EOF
+if compile_prog "" "$pthread_lib" ; then
+  pthread_setname_np=yes
+fi
+
 ##########################################
 # rbd probe
 if test "$rbd" != "no" ; then
@@ -4628,6 +4646,16 @@ if test "$rdma" = "yes" ; then
   echo "CONFIG_RDMA=y" >> $config_host_mak
 fi
 
+# Hold two types of flag:
+#   CONFIG_THREAD_SETNAME_BYTHREAD  - we've got a way of setting the name on
+#                                     a thread we have a handle to
+#   CONFIG_PTHREAD_SETNAME_NP       - A way of doing it on a particular
+#                                     platform
+if test "$pthread_setname_np" = "yes" ; then
+  echo "CONFIG_THREAD_SETNAME_BYTHREAD=y" >> $config_host_mak
+  echo "CONFIG_PTHREAD_SETNAME_NP=y" >> $config_host_mak
+fi
+
 if test "$tcg_interpreter" = "yes"; then
   QEMU_INCLUDES="-I\$(SRC_PATH)/tcg/tci $QEMU_INCLUDES"
 elif test "$ARCH" = "sparc64" ; then

util/qemu-thread-posix.c

@@ -32,6 +32,13 @@ static bool name_threads;
 void qemu_thread_naming(bool enable)
 {
     name_threads = enable;
+
+#ifndef CONFIG_THREAD_SETNAME_BYTHREAD
+    /* This is a debugging option, not fatal */
+    if (enable) {
+        fprintf(stderr, "qemu: thread naming not supported on this host\n");
+    }
+#endif
 }
 
 static void error_exit(int err, const char *msg)
@@ -394,6 +401,16 @@ void qemu_event_wait(QemuEvent *ev)
     }
 }
 
+/* Attempt to set the threads name; note that this is for debug, so
+ * we're not going to fail if we can't set it.
+ */
+static void qemu_thread_set_name(QemuThread *thread, const char *name)
+{
+#ifdef CONFIG_PTHREAD_SETNAME_NP
+    pthread_setname_np(thread->thread, name);
+#endif
+}
+
 void qemu_thread_create(QemuThread *thread, const char *name,
                        void *(*start_routine)(void*),
                        void *arg, int mode)
@@ -420,11 +437,9 @@ void qemu_thread_create(QemuThread *thread, const char *name,
     if (err)
         error_exit(err, __func__);
 
-#if defined(__GLIBC__) && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 12))
     if (name_threads) {
-        pthread_setname_np(thread->thread, name);
+        qemu_thread_set_name(thread, name);
     }
-#endif
 
     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 

util/qemu-thread-win32.c

@@ -22,6 +22,8 @@ void qemu_thread_naming(bool enable)
 {
     /* But note we don't actually name them on Windows yet */
     name_threads = enable;
+
+    fprintf(stderr, "qemu: thread naming not supported on this host\n");
 }
 
 static void error_exit(int err, const char *msg)