[Spice-devel] [spice-common 3/3] log: Make sure glib threading is initialized

[Christophe Fergeau]

While testing spice-server on EL6, I was getting random crashes in the
glib logging code because g_logv was called recursively even though this
was not visible in a backtrace.

It turns out on older glib versions (EL6 has 2.28), g_logv is not
thread-safe unless g_thread_init() is called first. If g_thread_init()
is not called, the GMutex/GPrivate calls g_logv makes are turned into
no-ops, which is going to cause the recursion issue I was seeing.

This commit adds a call to g_thread_init() for these older glib
versions.

(gdb) bt
    0x7fff9f9fb110 "item.type: 114", unused_data=0x0) at gmessages.c:863
    format=0x7ffff50e72ac "item.type: %d", args1=0x7fff9f9fb640) at gmessages.c:517
    SPICE_LOG_LEVEL_DEBUG, strloc=0x7ffff50e72ba "dcc.c:1652", function=
    0x7ffff50e7320 "release_item_before_push", format=0x7ffff50e72ac "item.type: %d", args=
    0x7fff9f9fb640) at log.c:163
    SPICE_LOG_LEVEL_DEBUG, strloc=0x7ffff50e72ba "dcc.c:1652", function=
    0x7ffff50e7320 "release_item_before_push", format=0x7ffff50e72ac "item.type: %d") at log.c:195
    at dcc.c:1652
    at dcc.c:1719
    at dcc-send.c:2450
    at red-channel.c:578
    at red-channel.c:1587
    at event-loop.c:122
    0x7ffff4fb2ef2 <watch_func>, user_data=0x7fff980244e0) at giounix.c:166
    0x7ffff86ec770) at gmain.c:3092
---
 common/log.c     | 8 ++++++++
 m4/spice-deps.m4 | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/common/log.c b/common/log.c
index d4a6d28..e39eefc 100644
--- a/common/log.c
+++ b/common/log.c
@@ -138,6 +138,14 @@ SPICE_CONSTRUCTOR_FUNC(spice_log_init)
     g_log_set_handler(SPICE_LOG_DOMAIN,
                       G_LOG_LEVEL_MASK | G_LOG_FLAG_FATAL | G_LOG_FLAG_RECURSION,
                       spice_logger, NULL);
+    /* Threading is always enabled from 2.31.0 onwards */
+    /* Our logging is potentially used from different threads.
+     * Older glibs require that g_thread_init() is called when
+     * doing that. */
+#if !GLIB_CHECK_VERSION(2, 31, 0)
+    if (!g_thread_supported())
+        g_thread_init(NULL);
+#endif
 }
 
 static void spice_logv(const char *log_domain,
diff --git a/m4/spice-deps.m4 b/m4/spice-deps.m4
index fb43cd2..170adf2 100644
--- a/m4/spice-deps.m4
+++ b/m4/spice-deps.m4
@@ -173,7 +173,7 @@ AC_DEFUN([SPICE_CHECK_PIXMAN], [
 # use in the GLIB2_CFLAGS and GLIB2_LIBS variables.
 #------------------
 AC_DEFUN([SPICE_CHECK_GLIB2], [
-    PKG_CHECK_MODULES(GLIB2, glib-2.0 >= 2.22 gio-2.0 >= 2.22)
+    PKG_CHECK_MODULES(GLIB2, glib-2.0 >= 2.22 gio-2.0 >= 2.22 gthread-2.0 >= 2.22)
 ])
 
 # SPICE_CHECK_PYTHON_MODULES()
-- 
2.5.5