Re: [Qemu-devel] [PATCH v3] qemu-char: don't issue CHR_EVENT_OPEN in a BH

[mdroth]

On Tue, Jun 04, 2013 at 11:58:12AM +0200, Hans de Goede wrote:
> Hi,
> 
> On 06/03/2013 10:25 PM, Michael Roth wrote:
> 
> <snip>
> 
> >To fix these, let's just drop the BH.
> >
> >Since the initial reasoning for using it still applies to an extent,
> >work around that by deferring the delivery of CHR_EVENT_OPENED until
> >after the chardevs have been fully initialized, toward the end of
> >qmp_chardev_add() (or some cases, qemu_chr_new_from_opts()). This
> >defers delivery long enough that we can be assured a CharDriverState
> >is fully initialized before CHR_EVENT_OPENED is sent.
> >
> >Also, rather than requiring each chardev to do an explicit open, do it
> >automatically, and allow the small few who don't desire such behavior to
> >suppress the OPENED-on-init behavior by setting a
> >'suppress_be_open_on_init' flag.
> >
> >We additionally add missing OPENED events for stdio backends on w32,
> >which were previously not being issued, causing us to not recieve the
> >banner and initial prompts for qmp/hmp.
> 
> 2 remarks:
> 
> 1) We already have something very similar to suppress_be_open_on_init
> on the frontend side, it is called explicit_fe_open, I suggest calling
> the backend variant explicit_be_open for consistency

I think the naming is a bit confusing at first glance, but the behavior
does seem consistent with what we're trying to do for backends, so I'll
go ahead and make the change for v4.

> 
> 2) It would be good to do a full audit to check if you've caught all
> backends which need suppress_be_open_on_init:
> a) check all callers of register_char_driver*
> b) check if their open method calls qemu_chr_be_generic_open
> c) if it does not they need suppress_be_open_on_init
> 

Agreed; that was the intention here, but it looks like I missed some.

> You've missed at least the spicevmc & spiceport backends,
> which both need suppress_be_open_on_init

Looks like we need one for qemu_chr_open_msmouse() as well. Will fix
these in v4.

Thanks!

> 
> Regards,
> 
> Hans
> 
> 
> 
> 
> >
> >Reported-by: Stefan Priebe <address@hidden>
> >Cc: address@hidden
> >Signed-off-by: Michael Roth <address@hidden>
> >---
> >v2->v3:
> >  * removed artifact in from v1 in backends/baum.c, test build with
> >    BRLAPI=y (Anthony)
> >  * rebased on latest origin/master
> >
> >v1->v2:
> >  * default to sending OPENED on backend init, add flag to suppress
> >    it (Anthony)
> >  * fix missing OPENED for stdio backends on w32
> >  * fix missing OPENED when qemu_chr_new_from_opts() doesn't use
> >    qmp_chardev_add()
> >  * clean up/update commit message
> >
> >  backends/baum.c       |    2 --
> >  include/sysemu/char.h |    2 +-
> >  qemu-char.c           |   38 +++++++++++++++++---------------------
> >  ui/console.c          |    1 -
> >  ui/gtk.c              |    1 -
> >  5 files changed, 18 insertions(+), 26 deletions(-)
> >
> >diff --git a/backends/baum.c b/backends/baum.c
> >index 4cba79f..62aa784 100644
> >--- a/backends/baum.c
> >+++ b/backends/baum.c
> >@@ -611,8 +611,6 @@ CharDriverState *chr_baum_init(void)
> >
> >      qemu_set_fd_handler(baum->brlapi_fd, baum_chr_read, NULL, baum);
> >
> >-    qemu_chr_be_generic_open(chr);
> >-
> >      return chr;
> >
> >  fail:
> >diff --git a/include/sysemu/char.h b/include/sysemu/char.h
> >index 5e42c90..b0ae749 100644
> >--- a/include/sysemu/char.h
> >+++ b/include/sysemu/char.h
> >@@ -70,13 +70,13 @@ struct CharDriverState {
> >      void (*chr_set_echo)(struct CharDriverState *chr, bool echo);
> >      void (*chr_set_fe_open)(struct CharDriverState *chr, int fe_open);
> >      void *opaque;
> >-    int idle_tag;
> >      char *label;
> >      char *filename;
> >      int be_open;
> >      int fe_open;
> >      int explicit_fe_open;
> >      int avail_connections;
> >+    bool suppress_be_open_on_init;
> >      QemuOpts *opts;
> >      QTAILQ_ENTRY(CharDriverState) next;
> >  };
> >diff --git a/qemu-char.c b/qemu-char.c
> >index d04b429..8043f86 100644
> >--- a/qemu-char.c
> >+++ b/qemu-char.c
> >@@ -110,19 +110,9 @@ void qemu_chr_be_event(CharDriverState *s, int event)
> >      s->chr_event(s->handler_opaque, event);
> >  }
> >
> >-static gboolean qemu_chr_be_generic_open_bh(gpointer opaque)
> >-{
> >-    CharDriverState *s = opaque;
> >-    qemu_chr_be_event(s, CHR_EVENT_OPENED);
> >-    s->idle_tag = 0;
> >-    return FALSE;
> >-}
> >-
> >  void qemu_chr_be_generic_open(CharDriverState *s)
> >  {
> >-    if (s->idle_tag == 0) {
> >-        s->idle_tag = g_idle_add(qemu_chr_be_generic_open_bh, s);
> >-    }
> >+    qemu_chr_be_event(s, CHR_EVENT_OPENED);
> >  }
> >
> >  int qemu_chr_fe_write(CharDriverState *s, const uint8_t *buf, int len)
> >@@ -247,6 +237,7 @@ static CharDriverState *qemu_chr_open_null(void)
> >
> >      chr = g_malloc0(sizeof(CharDriverState));
> >      chr->chr_write = null_chr_write;
> >+    chr->suppress_be_open_on_init = true;
> >      return chr;
> >  }
> >
> >@@ -504,9 +495,6 @@ static CharDriverState 
> >*qemu_chr_open_mux(CharDriverState *drv)
> >      /* Frontend guest-open / -close notification is not support with muxes 
> > */
> >      chr->chr_set_fe_open = NULL;
> >
> >-    /* Muxes are always open on creation */
> >-    qemu_chr_be_generic_open(chr);
> >-
> >      return chr;
> >  }
> >
> >@@ -883,8 +871,6 @@ static CharDriverState *qemu_chr_open_fd(int fd_in, int 
> >fd_out)
> >      chr->chr_update_read_handler = fd_chr_update_read_handler;
> >      chr->chr_close = fd_chr_close;
> >
> >-    qemu_chr_be_generic_open(chr);
> >-
> >      return chr;
> >  }
> >
> >@@ -1243,6 +1229,7 @@ static CharDriverState *qemu_chr_open_pty(const char 
> >*id,
> >      chr->chr_update_read_handler = pty_chr_update_read_handler;
> >      chr->chr_close = pty_chr_close;
> >      chr->chr_add_watch = pty_chr_add_watch;
> >+    chr->suppress_be_open_on_init = true;
> >
> >      s->fd = io_channel_from_fd(master_fd);
> >      s->timer_tag = 0;
> >@@ -1595,8 +1582,6 @@ static CharDriverState *qemu_chr_open_pp_fd(int fd)
> >      chr->chr_close = pp_close;
> >      chr->opaque = drv;
> >
> >-    qemu_chr_be_generic_open(chr);
> >-
> >      return chr;
> >  }
> >  #endif /* __linux__ */
> >@@ -1650,6 +1635,7 @@ static CharDriverState *qemu_chr_open_pp_fd(int fd)
> >      chr->opaque = (void *)(intptr_t)fd;
> >      chr->chr_write = null_chr_write;
> >      chr->chr_ioctl = pp_ioctl;
> >+    chr->suppress_be_open_on_init = true;
> >      return chr;
> >  }
> >  #endif
> >@@ -1880,7 +1866,6 @@ static CharDriverState *qemu_chr_open_win_path(const 
> >char *filename)
> >          g_free(chr);
> >          return NULL;
> >      }
> >-    qemu_chr_be_generic_open(chr);
> >      return chr;
> >  }
> >
> >@@ -1980,7 +1965,6 @@ static CharDriverState 
> >*qemu_chr_open_pipe(ChardevHostdev *opts)
> >          g_free(chr);
> >          return NULL;
> >      }
> >-    qemu_chr_be_generic_open(chr);
> >      return chr;
> >  }
> >
> >@@ -1994,7 +1978,6 @@ static CharDriverState *qemu_chr_open_win_file(HANDLE 
> >fd_out)
> >      s->hcom = fd_out;
> >      chr->opaque = s;
> >      chr->chr_write = win_chr_write;
> >-    qemu_chr_be_generic_open(chr);
> >      return chr;
> >  }
> >
> >@@ -2329,6 +2312,8 @@ static CharDriverState *qemu_chr_open_udp_fd(int fd)
> >      chr->chr_write = udp_chr_write;
> >      chr->chr_update_read_handler = udp_chr_update_read_handler;
> >      chr->chr_close = udp_chr_close;
> >+    /* be isn't opened until we get a connection */
> >+    chr->suppress_be_open_on_init = true;
> >      return chr;
> >  }
> >
> >@@ -2731,6 +2716,8 @@ static CharDriverState *qemu_chr_open_socket_fd(int 
> >fd, bool do_nodelay,
> >      chr->get_msgfd = tcp_get_msgfd;
> >      chr->chr_add_client = tcp_chr_add_client;
> >      chr->chr_add_watch = tcp_chr_add_watch;
> >+    /* be isn't opened until we get a connection */
> >+    chr->suppress_be_open_on_init = true;
> >
> >      if (is_listen) {
> >          s->listen_fd = fd;
> >@@ -3325,6 +3312,12 @@ CharDriverState *qemu_chr_new_from_opts(QemuOpts 
> >*opts,
> >      if (!chr->filename)
> >          chr->filename = g_strdup(qemu_opt_get(opts, "backend"));
> >      chr->init = init;
> >+    /* if we didn't create the chardev via qmp_chardev_add, we
> >+     * need to send the OPENED event here
> >+     */
> >+    if (!chr->suppress_be_open_on_init) {
> >+        qemu_chr_be_event(chr, CHR_EVENT_OPENED);
> >+    }
> >      QTAILQ_INSERT_TAIL(&chardevs, chr, next);
> >
> >      if (qemu_opt_get_bool(opts, "mux", 0)) {
> >@@ -3804,6 +3797,9 @@ ChardevReturn *qmp_chardev_add(const char *id, 
> >ChardevBackend *backend,
> >          if (!chr->filename) {
> >              chr->filename = 
> > g_strdup(ChardevBackendKind_lookup[backend->kind]);
> >          }
> >+        if (!chr->suppress_be_open_on_init) {
> >+            qemu_chr_be_event(chr, CHR_EVENT_OPENED);
> >+        }
> >          QTAILQ_INSERT_TAIL(&chardevs, chr, next);
> >          return ret;
> >      } else {
> >diff --git a/ui/console.c b/ui/console.c
> >index b30853f..54b192d 100644
> >--- a/ui/console.c
> >+++ b/ui/console.c
> >@@ -1746,7 +1746,6 @@ static void text_console_do_init(CharDriverState *chr, 
> >DisplayState *ds)
> >          s->t_attrib = s->t_attrib_default;
> >      }
> >
> >-    qemu_chr_be_generic_open(chr);
> >      if (chr->init)
> >          chr->init(chr);
> >  }
> >diff --git a/ui/gtk.c b/ui/gtk.c
> >index 52c3f95..71b2497 100644
> >--- a/ui/gtk.c
> >+++ b/ui/gtk.c
> >@@ -1214,7 +1214,6 @@ static GSList *gd_vc_init(GtkDisplayState *s, 
> >VirtualConsole *vc, int index, GSL
> >
> >      gtk_menu_shell_append(GTK_MENU_SHELL(view_menu), vc->menu_item);
> >
> >-    qemu_chr_be_generic_open(vc->chr);
> >      if (vc->chr->init) {
> >          vc->chr->init(vc->chr);
> >      }
> >
>