[PATCH 4/4] chardev: Introduce a lock for hup_source

[Fabiano Rosas]

It's possible for the hup_source to have its reference decremented by
remove_hup_source() while it's still being added to the context,
leading to asserts in glib:

g_source_set_callback_indirect: assertion 'g_atomic_int_get
(&source->ref_count) > 0'

g_source_attach: assertion 'g_atomic_int_get (&source->ref_count) > 0'
failed

Add a lock to serialize removal and creation.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 chardev/char-socket.c  | 4 ++++
 chardev/char.c         | 2 ++
 include/chardev/char.h | 1 +
 3 files changed, 7 insertions(+)

diff --git a/chardev/char-socket.c b/chardev/char-socket.c
index d16608f1ed..88db9acd0d 100644
--- a/chardev/char-socket.c
+++ b/chardev/char-socket.c
@@ -374,7 +374,9 @@ static void tcp_chr_free_connection(Chardev *chr)
         s->read_msgfds_num = 0;
     }
 
+    qemu_mutex_lock(&chr->hup_source_lock);
     remove_hup_source(s);
+    qemu_mutex_unlock(&chr->hup_source_lock);
 
     tcp_set_msgfds(chr, NULL, 0);
     remove_fd_in_watch(chr);
@@ -613,6 +615,7 @@ static void update_ioc_handlers(SocketChardev *s)
                                      tcp_chr_read, chr,
                                      chr->gcontext);
 
+    qemu_mutex_lock(&chr->hup_source_lock);
     remove_hup_source(s);
     s->hup_source = qio_channel_create_watch(s->ioc, G_IO_HUP);
     /*
@@ -634,6 +637,7 @@ static void update_ioc_handlers(SocketChardev *s)
     g_source_set_callback(s->hup_source, (GSourceFunc)tcp_chr_hup,
                           chr, NULL);
     g_source_attach(s->hup_source, chr->gcontext);
+    qemu_mutex_unlock(&chr->hup_source_lock);
 }
 
 static void tcp_chr_connect(void *opaque)
diff --git a/chardev/char.c b/chardev/char.c
index bbebd246c3..d03f698b38 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -279,6 +279,7 @@ static void char_init(Object *obj)
     chr->handover_yank_instance = false;
     chr->logfd = -1;
     qemu_mutex_init(&chr->chr_write_lock);
+    qemu_mutex_init(&chr->hup_source_lock);
 
     /*
      * Assume if chr_update_read_handler is implemented it will
@@ -316,6 +317,7 @@ static void char_finalize(Object *obj)
         close(chr->logfd);
     }
     qemu_mutex_destroy(&chr->chr_write_lock);
+    qemu_mutex_destroy(&chr->hup_source_lock);
 }
 
 static const TypeInfo char_type_info = {
diff --git a/include/chardev/char.h b/include/chardev/char.h
index 429852f8d9..064184153d 100644
--- a/include/chardev/char.h
+++ b/include/chardev/char.h
@@ -60,6 +60,7 @@ struct Chardev {
     Object parent_obj;
 
     QemuMutex chr_write_lock;
+    QemuMutex hup_source_lock;
     CharBackend *be;
     char *label;
     char *filename;
-- 
2.35.3