Commit ae2990c2 authored by Stefan Hajnoczi's avatar Stefan Hajnoczi
Browse files

osdep: initialize glib threads in all QEMU tools 



glib versions prior to 2.31.0 require an explicit g_thread_init() call
to enable multi-threading.

Failure to initialize threading causes glib to take single-threaded code
paths without synchronization.  For example, the g_slice allocator will
crash due to race conditions.

Fix this for all QEMU tool programs (qemu-nbd, qemu-io, qemu-img) by
moving the g_thread_init() call from vl.c:main() into a new
osdep.c:thread_init() constructor function.

thread_init() has __attribute__((constructor)) and is automatically
invoked by the runtime during startup.

We can now drop the "simple" trace backend's g_thread_init() call since
thread_init() already called it.

Note that we must keep coroutine-gthread.c's g_thread_init() call which
is located in a constructor function.  There is no guarantee for
constructor function ordering so thread_init() may only be called later.

Reported-by: default avatarMario de Chenno <mario.dechenno@unina2.it>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 839a5547

trace/simple.c

+0 −9
Original line number Diff line number Diff line
@@ -414,15 +414,6 @@ bool trace_backend_init(const char *events, const char *file) 
{

    GThread *thread;



    if (!g_thread_supported()) {

#if !GLIB_CHECK_VERSION(2, 31, 0)

        g_thread_init(NULL);

#else

        fprintf(stderr, "glib threading failed to initialize.\n");

        exit(1);

#endif

    }



#if !GLIB_CHECK_VERSION(2, 31, 0)

    trace_available_cond = g_cond_new();

    trace_empty_cond = g_cond_new();

util/osdep.c

+18 −0
Original line number Diff line number Diff line
@@ -436,6 +436,24 @@ int socket_init(void) 
    return 0;

}



/* Ensure that glib is running in multi-threaded mode */

static void __attribute__((constructor)) thread_init(void)

{

    if (!g_thread_supported()) {

#if !GLIB_CHECK_VERSION(2, 31, 0)

        /* Old versions of glib require explicit initialization.  Failure to do

         * this results in the single-threaded code paths being taken inside

         * glib.  For example, the g_slice allocator will not be thread-safe

         * and cause crashes.

         */

        g_thread_init(NULL);

#else

        fprintf(stderr, "glib threading failed to initialize.\n");

        exit(1);

#endif

    }

}



#ifndef CONFIG_IOVEC

/* helper function for iov_send_recv() */

static ssize_t

vl.c

+0 −8
Original line number Diff line number Diff line
@@ -2970,14 +2970,6 @@ int main(int argc, char **argv, char **envp) 
    qemu_init_exec_dir(argv[0]);



    g_mem_set_vtable(&mem_trace);

    if (!g_thread_supported()) {

#if !GLIB_CHECK_VERSION(2, 31, 0)

        g_thread_init(NULL);

#else

        fprintf(stderr, "glib threading failed to initialize.\n");

        exit(1);

#endif

    }



    module_call_init(MODULE_INIT_QOM);