[Qemu-devel] [PATCH v3 0/2] chardev: fix mess in OPENED/CLOSED events when muxed

[Qemu-devel] [PATCH v3 0/2] chardev: fix mess in OPENED/CLOSED events when muxed

[Artem Pisarenko]

This issue actually more complex. Idea of generating events from inside function called '*_set_handlers' isn't good, at least its implicit nature, and especially a fact, that function decides about open state (see 'fe_open' variable), but generates event only in one direction. Combined with 'mux_chr_set_handlers()' hack this makes things even worse.
Better solution is to change fe interface and rewrite all frontends code (a lot of stuff in hw/char/* and somewhere else).
Although first patch doesn't fix any bug (known to me), its main effect is optimization of emulation performance by avoiding extra activity.
Added testing demonstrates issue and prevents potential bugs in future.

v3 changes:
 - extended commit message explaining fix (as supposed by Marc-André Lureau)

v2 changes:
 - fix failed unit test
 - 'mux_chr_set_handlers()' hack rewritten (as supposed by Marc-André Lureau)
 - added testing of issue to unit test (new patch)

Artem Pisarenko (2):
  chardev: fix mess in OPENED/CLOSED events when muxed
  tests/test-char: add muxed chardev testing for open/close

 chardev/char-fe.c         | 33 +++++++++++++------
 chardev/char-mux.c        | 16 +++++-----
 include/chardev/char-fe.h | 18 ++++++++++-
 tests/test-char.c         | 80 +++++++++++++++++++++++++++++++++++++++++++++--
 4 files changed, 127 insertions(+), 20 deletions(-)

-- 
2.7.4

[Qemu-devel] [PATCH v3 1/2] chardev: fix mess in OPENED/CLOSED events when muxed

[Artem Pisarenko]

When chardev is multiplexed (mux=on) there are a lot of cases where
CHR_EVENT_OPENED/CHR_EVENT_CLOSED events pairing (expected from
frontend side) is broken. There are either generation of multiple
repeated or extra CHR_EVENT_OPENED events, or CHR_EVENT_CLOSED just
isn't generated at all.
This is mostly because 'qemu_chr_fe_set_handlers()' function makes its
own (and often wrong) implicit decision on updated frontend state and
invokes 'fd_event' callback with 'CHR_EVENT_OPENED'. And even worse,
it doesn't do symmetric action in opposite direction, as someone may
expect (i.e. it doesn't invoke previously set 'fd_event' with
'CHR_EVENT_CLOSED'). Muxed chardev uses trick by calling this function
again to replace callback handlers with its own ones, but it doesn't
account for such side effect.
Fix that using extended version of this function with added argument
for disabling side effect and keep original function for compatibility
with lots of frontends already using this interface and being
"tolerant" to its side effects.
One more source of event duplication is just line of code in
char-mux.c, which does far more than comment above says (obvious fix).

Signed-off-by: Artem Pisarenko <artem.k.pisarenko@gmail.com>
---

Notes:
    v3:
     - extended and improved commit message with 'why' and 'how' explanation

 chardev/char-fe.c         | 33 ++++++++++++++++++++++++---------
 chardev/char-mux.c        | 16 ++++++++--------
 include/chardev/char-fe.h | 18 +++++++++++++++++-
 3 files changed, 49 insertions(+), 18 deletions(-)

diff --git a/chardev/char-fe.c b/chardev/char-fe.c
index a8931f7..b7bcbd5 100644
--- a/chardev/char-fe.c
+++ b/chardev/char-fe.c
@@ -246,14 +246,15 @@ void qemu_chr_fe_deinit(CharBackend *b, bool del)
     }
 }
 
-void qemu_chr_fe_set_handlers(CharBackend *b,
-                              IOCanReadHandler *fd_can_read,
-                              IOReadHandler *fd_read,
-                              IOEventHandler *fd_event,
-                              BackendChangeHandler *be_change,
-                              void *opaque,
-                              GMainContext *context,
-                              bool set_open)
+void qemu_chr_fe_set_handlers_full(CharBackend *b,
+                                   IOCanReadHandler *fd_can_read,
+                                   IOReadHandler *fd_read,
+                                   IOEventHandler *fd_event,
+                                   BackendChangeHandler *be_change,
+                                   void *opaque,
+                                   GMainContext *context,
+                                   bool set_open,
+                                   bool sync_state)
 {
     Chardev *s;
     int fe_open;
@@ -285,7 +286,7 @@ void qemu_chr_fe_set_handlers(CharBackend *b,
         qemu_chr_fe_take_focus(b);
         /* We're connecting to an already opened device, so let's make sure we
            also get the open event */
-        if (s->be_open) {
+        if (sync_state && s->be_open) {
             qemu_chr_be_event(s, CHR_EVENT_OPENED);
         }
     }
@@ -295,6 +296,20 @@ void qemu_chr_fe_set_handlers(CharBackend *b,
     }
 }
 
+void qemu_chr_fe_set_handlers(CharBackend *b,
+                              IOCanReadHandler *fd_can_read,
+                              IOReadHandler *fd_read,
+                              IOEventHandler *fd_event,
+                              BackendChangeHandler *be_change,
+                              void *opaque,
+                              GMainContext *context,
+                              bool set_open)
+{
+    qemu_chr_fe_set_handlers_full(b, fd_can_read, fd_read, fd_event, be_change,
+                                  opaque, context, set_open,
+                                  true);
+}
+
 void qemu_chr_fe_take_focus(CharBackend *b)
 {
     if (!b->chr) {
diff --git a/chardev/char-mux.c b/chardev/char-mux.c
index 6055e76..1199d32 100644
--- a/chardev/char-mux.c
+++ b/chardev/char-mux.c
@@ -283,13 +283,13 @@ void mux_chr_set_handlers(Chardev *chr, GMainContext *context)
     MuxChardev *d = MUX_CHARDEV(chr);
 
     /* Fix up the real driver with mux routines */
-    qemu_chr_fe_set_handlers(&d->chr,
-                             mux_chr_can_read,
-                             mux_chr_read,
-                             mux_chr_event,
-                             NULL,
-                             chr,
-                             context, true);
+    qemu_chr_fe_set_handlers_full(&d->chr,
+                                  mux_chr_can_read,
+                                  mux_chr_read,
+                                  mux_chr_event,
+                                  NULL,
+                                  chr,
+                                  context, true, false);
 }
 
 void mux_set_focus(Chardev *chr, int focus)
@@ -367,7 +367,7 @@ static int open_muxes(Chardev *chr)
      * mark mux as OPENED so any new FEs will immediately receive
      * OPENED event
      */
-    qemu_chr_be_event(chr, CHR_EVENT_OPENED);
+    chr->be_open = 1;
 
     return 0;
 }
diff --git a/include/chardev/char-fe.h b/include/chardev/char-fe.h
index 46c997d..c1b7fd9 100644
--- a/include/chardev/char-fe.h
+++ b/include/chardev/char-fe.h
@@ -67,7 +67,7 @@ bool qemu_chr_fe_backend_connected(CharBackend *be);
 bool qemu_chr_fe_backend_open(CharBackend *be);
 
 /**
- * qemu_chr_fe_set_handlers:
+ * qemu_chr_fe_set_handlers_full:
  * @b: a CharBackend
  * @fd_can_read: callback to get the amount of data the frontend may
  *               receive
@@ -79,12 +79,28 @@ bool qemu_chr_fe_backend_open(CharBackend *be);
  * @context: a main loop context or NULL for the default
  * @set_open: whether to call qemu_chr_fe_set_open() implicitely when
  * any of the handler is non-NULL
+ * @sync_state: whether to issue event callback with updated state
  *
  * Set the front end char handlers. The front end takes the focus if
  * any of the handler is non-NULL.
  *
  * Without associated Chardev, nothing is changed.
  */
+void qemu_chr_fe_set_handlers_full(CharBackend *b,
+                                   IOCanReadHandler *fd_can_read,
+                                   IOReadHandler *fd_read,
+                                   IOEventHandler *fd_event,
+                                   BackendChangeHandler *be_change,
+                                   void *opaque,
+                                   GMainContext *context,
+                                   bool set_open,
+                                   bool sync_state);
+
+/**
+ * qemu_chr_fe_set_handlers:
+ *
+ * Version of qemu_chr_fe_set_handlers_full() with sync_state = true.
+ */
 void qemu_chr_fe_set_handlers(CharBackend *b,
                               IOCanReadHandler *fd_can_read,
                               IOReadHandler *fd_read,
-- 
2.7.4

[Qemu-devel] [PATCH v3 2/2] tests/test-char: add muxed chardev testing for open/close

[Artem Pisarenko]

Validate that frontend callbacks for CHR_EVENT_OPENED/CHR_EVENT_CLOSED
events are being issued when expected and in strictly pairing order.

Signed-off-by: Artem Pisarenko <artem.k.pisarenko@gmail.com>
---
 tests/test-char.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 78 insertions(+), 2 deletions(-)

diff --git a/tests/test-char.c b/tests/test-char.c
index 831e37f..657cb4c 100644
--- a/tests/test-char.c
+++ b/tests/test-char.c
@@ -16,6 +16,9 @@ static bool quit;
 
 typedef struct FeHandler {
     int read_count;
+    bool is_open;
+    int openclose_count;
+    bool openclose_mismatch;
     int last_event;
     char read_buf[128];
 } FeHandler;
@@ -49,10 +52,24 @@ static void fe_read(void *opaque, const uint8_t *buf, int size)
 static void fe_event(void *opaque, int event)
 {
     FeHandler *h = opaque;
+    bool new_open_state;
 
     h->last_event = event;
-    if (event != CHR_EVENT_BREAK) {
+    switch (event) {
+    case CHR_EVENT_BREAK:
+        break;
+    case CHR_EVENT_OPENED:
+    case CHR_EVENT_CLOSED:
+        h->openclose_count++;
+        new_open_state = (event == CHR_EVENT_OPENED);
+        if (h->is_open == new_open_state) {
+            h->openclose_mismatch = true;
+        }
+        h->is_open = new_open_state;
+        /* no break */
+    default:
         quit = true;
+        break;
     }
 }
 
@@ -161,7 +178,7 @@ static void char_mux_test(void)
     QemuOpts *opts;
     Chardev *chr, *base;
     char *data;
-    FeHandler h1 = { 0, }, h2 = { 0, };
+    FeHandler h1 = { 0, false, 0, false, }, h2 = { 0, false, 0, false, };
     CharBackend chr_be1, chr_be2;
 
     opts = qemu_opts_create(qemu_find_opts("chardev"), "mux-label",
@@ -233,6 +250,65 @@ static void char_mux_test(void)
     g_assert_cmpint(h1.last_event, ==, CHR_EVENT_BREAK);
     g_assert_cmpint(h2.last_event, ==, CHR_EVENT_MUX_OUT);
 
+    /* open/close state and corresponding events */
+    g_assert_true(qemu_chr_fe_backend_open(&chr_be1));
+    g_assert_true(qemu_chr_fe_backend_open(&chr_be2));
+    g_assert_true(h1.is_open);
+    g_assert_false(h1.openclose_mismatch);
+    g_assert_true(h2.is_open);
+    g_assert_false(h2.openclose_mismatch);
+
+    h1.openclose_count = h2.openclose_count = 0;
+
+    qemu_chr_fe_set_handlers(&chr_be1, NULL, NULL, NULL, NULL,
+                             NULL, NULL, false);
+    qemu_chr_fe_set_handlers(&chr_be2, NULL, NULL, NULL, NULL,
+                             NULL, NULL, false);
+    g_assert_cmpint(h1.openclose_count, ==, 0);
+    g_assert_cmpint(h2.openclose_count, ==, 0);
+
+    h1.is_open = h2.is_open = false;
+    qemu_chr_fe_set_handlers(&chr_be1,
+                             NULL,
+                             NULL,
+                             fe_event,
+                             NULL,
+                             &h1,
+                             NULL, false);
+    qemu_chr_fe_set_handlers(&chr_be2,
+                             NULL,
+                             NULL,
+                             fe_event,
+                             NULL,
+                             &h2,
+                             NULL, false);
+    g_assert_cmpint(h1.openclose_count, ==, 1);
+    g_assert_false(h1.openclose_mismatch);
+    g_assert_cmpint(h2.openclose_count, ==, 1);
+    g_assert_false(h2.openclose_mismatch);
+
+    qemu_chr_be_event(base, CHR_EVENT_CLOSED);
+    qemu_chr_be_event(base, CHR_EVENT_OPENED);
+    g_assert_cmpint(h1.openclose_count, ==, 3);
+    g_assert_false(h1.openclose_mismatch);
+    g_assert_cmpint(h2.openclose_count, ==, 3);
+    g_assert_false(h2.openclose_mismatch);
+
+    qemu_chr_fe_set_handlers(&chr_be2,
+                             fe_can_read,
+                             fe_read,
+                             fe_event,
+                             NULL,
+                             &h2,
+                             NULL, false);
+    qemu_chr_fe_set_handlers(&chr_be1,
+                             fe_can_read,
+                             fe_read,
+                             fe_event,
+                             NULL,
+                             &h1,
+                             NULL, false);
+
     /* remove first handler */
     qemu_chr_fe_set_handlers(&chr_be1, NULL, NULL, NULL, NULL,
                              NULL, NULL, true);
-- 
2.7.4

Re: [Qemu-devel] [PATCH v3 2/2] tests/test-char: add muxed chardev testing for open/close

[Marc-André Lureau]

On Tue, Nov 6, 2018 at 4:41 PM Artem Pisarenko
<artem.k.pisarenko@gmail.com> wrote:
>
> Validate that frontend callbacks for CHR_EVENT_OPENED/CHR_EVENT_CLOSED
> events are being issued when expected and in strictly pairing order.
>
> Signed-off-by: Artem Pisarenko <artem.k.pisarenko@gmail.com>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

> ---
>  tests/test-char.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 78 insertions(+), 2 deletions(-)
>
> diff --git a/tests/test-char.c b/tests/test-char.c
> index 831e37f..657cb4c 100644
> --- a/tests/test-char.c
> +++ b/tests/test-char.c
> @@ -16,6 +16,9 @@ static bool quit;
>
>  typedef struct FeHandler {
>      int read_count;
> +    bool is_open;
> +    int openclose_count;
> +    bool openclose_mismatch;
>      int last_event;
>      char read_buf[128];
>  } FeHandler;
> @@ -49,10 +52,24 @@ static void fe_read(void *opaque, const uint8_t *buf, int size)
>  static void fe_event(void *opaque, int event)
>  {
>      FeHandler *h = opaque;
> +    bool new_open_state;
>
>      h->last_event = event;
> -    if (event != CHR_EVENT_BREAK) {
> +    switch (event) {
> +    case CHR_EVENT_BREAK:
> +        break;
> +    case CHR_EVENT_OPENED:
> +    case CHR_EVENT_CLOSED:
> +        h->openclose_count++;
> +        new_open_state = (event == CHR_EVENT_OPENED);
> +        if (h->is_open == new_open_state) {
> +            h->openclose_mismatch = true;
> +        }
> +        h->is_open = new_open_state;
> +        /* no break */
> +    default:
>          quit = true;
> +        break;
>      }
>  }
>
> @@ -161,7 +178,7 @@ static void char_mux_test(void)
>      QemuOpts *opts;
>      Chardev *chr, *base;
>      char *data;
> -    FeHandler h1 = { 0, }, h2 = { 0, };
> +    FeHandler h1 = { 0, false, 0, false, }, h2 = { 0, false, 0, false, };
>      CharBackend chr_be1, chr_be2;
>
>      opts = qemu_opts_create(qemu_find_opts("chardev"), "mux-label",
> @@ -233,6 +250,65 @@ static void char_mux_test(void)
>      g_assert_cmpint(h1.last_event, ==, CHR_EVENT_BREAK);
>      g_assert_cmpint(h2.last_event, ==, CHR_EVENT_MUX_OUT);
>
> +    /* open/close state and corresponding events */
> +    g_assert_true(qemu_chr_fe_backend_open(&chr_be1));
> +    g_assert_true(qemu_chr_fe_backend_open(&chr_be2));
> +    g_assert_true(h1.is_open);
> +    g_assert_false(h1.openclose_mismatch);
> +    g_assert_true(h2.is_open);
> +    g_assert_false(h2.openclose_mismatch);
> +
> +    h1.openclose_count = h2.openclose_count = 0;
> +
> +    qemu_chr_fe_set_handlers(&chr_be1, NULL, NULL, NULL, NULL,
> +                             NULL, NULL, false);
> +    qemu_chr_fe_set_handlers(&chr_be2, NULL, NULL, NULL, NULL,
> +                             NULL, NULL, false);
> +    g_assert_cmpint(h1.openclose_count, ==, 0);
> +    g_assert_cmpint(h2.openclose_count, ==, 0);
> +
> +    h1.is_open = h2.is_open = false;
> +    qemu_chr_fe_set_handlers(&chr_be1,
> +                             NULL,
> +                             NULL,
> +                             fe_event,
> +                             NULL,
> +                             &h1,
> +                             NULL, false);
> +    qemu_chr_fe_set_handlers(&chr_be2,
> +                             NULL,
> +                             NULL,
> +                             fe_event,
> +                             NULL,
> +                             &h2,
> +                             NULL, false);
> +    g_assert_cmpint(h1.openclose_count, ==, 1);
> +    g_assert_false(h1.openclose_mismatch);
> +    g_assert_cmpint(h2.openclose_count, ==, 1);
> +    g_assert_false(h2.openclose_mismatch);
> +
> +    qemu_chr_be_event(base, CHR_EVENT_CLOSED);
> +    qemu_chr_be_event(base, CHR_EVENT_OPENED);
> +    g_assert_cmpint(h1.openclose_count, ==, 3);
> +    g_assert_false(h1.openclose_mismatch);
> +    g_assert_cmpint(h2.openclose_count, ==, 3);
> +    g_assert_false(h2.openclose_mismatch);
> +
> +    qemu_chr_fe_set_handlers(&chr_be2,
> +                             fe_can_read,
> +                             fe_read,
> +                             fe_event,
> +                             NULL,
> +                             &h2,
> +                             NULL, false);
> +    qemu_chr_fe_set_handlers(&chr_be1,
> +                             fe_can_read,
> +                             fe_read,
> +                             fe_event,
> +                             NULL,
> +                             &h1,
> +                             NULL, false);
> +
>      /* remove first handler */
>      qemu_chr_fe_set_handlers(&chr_be1, NULL, NULL, NULL, NULL,
>                               NULL, NULL, true);
> --
> 2.7.4
>

Re: [Qemu-devel] [PATCH v3 1/2] chardev: fix mess in OPENED/CLOSED events when muxed

[Marc-André Lureau]

On Tue, Nov 6, 2018 at 4:41 PM Artem Pisarenko
<artem.k.pisarenko@gmail.com> wrote:
>
> When chardev is multiplexed (mux=on) there are a lot of cases where
> CHR_EVENT_OPENED/CHR_EVENT_CLOSED events pairing (expected from
> frontend side) is broken. There are either generation of multiple
> repeated or extra CHR_EVENT_OPENED events, or CHR_EVENT_CLOSED just
> isn't generated at all.
> This is mostly because 'qemu_chr_fe_set_handlers()' function makes its
> own (and often wrong) implicit decision on updated frontend state and
> invokes 'fd_event' callback with 'CHR_EVENT_OPENED'. And even worse,
> it doesn't do symmetric action in opposite direction, as someone may
> expect (i.e. it doesn't invoke previously set 'fd_event' with
> 'CHR_EVENT_CLOSED'). Muxed chardev uses trick by calling this function
> again to replace callback handlers with its own ones, but it doesn't
> account for such side effect.
> Fix that using extended version of this function with added argument
> for disabling side effect and keep original function for compatibility
> with lots of frontends already using this interface and being
> "tolerant" to its side effects.
> One more source of event duplication is just line of code in
> char-mux.c, which does far more than comment above says (obvious fix).
>
> Signed-off-by: Artem Pisarenko <artem.k.pisarenko@gmail.com>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

> ---
>
> Notes:
>     v3:
>      - extended and improved commit message with 'why' and 'how' explanation
>
>  chardev/char-fe.c         | 33 ++++++++++++++++++++++++---------
>  chardev/char-mux.c        | 16 ++++++++--------
>  include/chardev/char-fe.h | 18 +++++++++++++++++-
>  3 files changed, 49 insertions(+), 18 deletions(-)
>
> diff --git a/chardev/char-fe.c b/chardev/char-fe.c
> index a8931f7..b7bcbd5 100644
> --- a/chardev/char-fe.c
> +++ b/chardev/char-fe.c
> @@ -246,14 +246,15 @@ void qemu_chr_fe_deinit(CharBackend *b, bool del)
>      }
>  }
>
> -void qemu_chr_fe_set_handlers(CharBackend *b,
> -                              IOCanReadHandler *fd_can_read,
> -                              IOReadHandler *fd_read,
> -                              IOEventHandler *fd_event,
> -                              BackendChangeHandler *be_change,
> -                              void *opaque,
> -                              GMainContext *context,
> -                              bool set_open)
> +void qemu_chr_fe_set_handlers_full(CharBackend *b,
> +                                   IOCanReadHandler *fd_can_read,
> +                                   IOReadHandler *fd_read,
> +                                   IOEventHandler *fd_event,
> +                                   BackendChangeHandler *be_change,
> +                                   void *opaque,
> +                                   GMainContext *context,
> +                                   bool set_open,
> +                                   bool sync_state)
>  {
>      Chardev *s;
>      int fe_open;
> @@ -285,7 +286,7 @@ void qemu_chr_fe_set_handlers(CharBackend *b,
>          qemu_chr_fe_take_focus(b);
>          /* We're connecting to an already opened device, so let's make sure we
>             also get the open event */
> -        if (s->be_open) {
> +        if (sync_state && s->be_open) {
>              qemu_chr_be_event(s, CHR_EVENT_OPENED);
>          }
>      }
> @@ -295,6 +296,20 @@ void qemu_chr_fe_set_handlers(CharBackend *b,
>      }
>  }
>
> +void qemu_chr_fe_set_handlers(CharBackend *b,
> +                              IOCanReadHandler *fd_can_read,
> +                              IOReadHandler *fd_read,
> +                              IOEventHandler *fd_event,
> +                              BackendChangeHandler *be_change,
> +                              void *opaque,
> +                              GMainContext *context,
> +                              bool set_open)
> +{
> +    qemu_chr_fe_set_handlers_full(b, fd_can_read, fd_read, fd_event, be_change,
> +                                  opaque, context, set_open,
> +                                  true);
> +}
> +
>  void qemu_chr_fe_take_focus(CharBackend *b)
>  {
>      if (!b->chr) {
> diff --git a/chardev/char-mux.c b/chardev/char-mux.c
> index 6055e76..1199d32 100644
> --- a/chardev/char-mux.c
> +++ b/chardev/char-mux.c
> @@ -283,13 +283,13 @@ void mux_chr_set_handlers(Chardev *chr, GMainContext *context)
>      MuxChardev *d = MUX_CHARDEV(chr);
>
>      /* Fix up the real driver with mux routines */
> -    qemu_chr_fe_set_handlers(&d->chr,
> -                             mux_chr_can_read,
> -                             mux_chr_read,
> -                             mux_chr_event,
> -                             NULL,
> -                             chr,
> -                             context, true);
> +    qemu_chr_fe_set_handlers_full(&d->chr,
> +                                  mux_chr_can_read,
> +                                  mux_chr_read,
> +                                  mux_chr_event,
> +                                  NULL,
> +                                  chr,
> +                                  context, true, false);
>  }
>
>  void mux_set_focus(Chardev *chr, int focus)
> @@ -367,7 +367,7 @@ static int open_muxes(Chardev *chr)
>       * mark mux as OPENED so any new FEs will immediately receive
>       * OPENED event
>       */
> -    qemu_chr_be_event(chr, CHR_EVENT_OPENED);
> +    chr->be_open = 1;
>
>      return 0;
>  }
> diff --git a/include/chardev/char-fe.h b/include/chardev/char-fe.h
> index 46c997d..c1b7fd9 100644
> --- a/include/chardev/char-fe.h
> +++ b/include/chardev/char-fe.h
> @@ -67,7 +67,7 @@ bool qemu_chr_fe_backend_connected(CharBackend *be);
>  bool qemu_chr_fe_backend_open(CharBackend *be);
>
>  /**
> - * qemu_chr_fe_set_handlers:
> + * qemu_chr_fe_set_handlers_full:
>   * @b: a CharBackend
>   * @fd_can_read: callback to get the amount of data the frontend may
>   *               receive
> @@ -79,12 +79,28 @@ bool qemu_chr_fe_backend_open(CharBackend *be);
>   * @context: a main loop context or NULL for the default
>   * @set_open: whether to call qemu_chr_fe_set_open() implicitely when
>   * any of the handler is non-NULL
> + * @sync_state: whether to issue event callback with updated state
>   *
>   * Set the front end char handlers. The front end takes the focus if
>   * any of the handler is non-NULL.
>   *
>   * Without associated Chardev, nothing is changed.
>   */
> +void qemu_chr_fe_set_handlers_full(CharBackend *b,
> +                                   IOCanReadHandler *fd_can_read,
> +                                   IOReadHandler *fd_read,
> +                                   IOEventHandler *fd_event,
> +                                   BackendChangeHandler *be_change,
> +                                   void *opaque,
> +                                   GMainContext *context,
> +                                   bool set_open,
> +                                   bool sync_state);
> +
> +/**
> + * qemu_chr_fe_set_handlers:
> + *
> + * Version of qemu_chr_fe_set_handlers_full() with sync_state = true.
> + */
>  void qemu_chr_fe_set_handlers(CharBackend *b,
>                                IOCanReadHandler *fd_can_read,
>                                IOReadHandler *fd_read,
> --
> 2.7.4
>