On Tue, 4 Jun 2013 16:35:09 -0500
Michael Roth <mdr...@linux.vnet.ibm.com> wrote:
> When CHR_EVENT_OPENED was initially added, it was CHR_EVENT_RESET,
> and it was issued as a bottom-half:
>
> 86e94dea5b740dad65446c857f6959eae43e0ba6
>
> Which we basically used to print out a greeting/prompt for the
> monitor.
>
> AFAICT the only reason this was ever done in a BH was because in
> some cases we'd modify the chr_write handler for a new chardev
> backend *after* the site where we issued the reset (see:
> 86e94d:qemu_chr_open_stdio())
>
> At some point this event was renamed to CHR_EVENT_OPENED, and we've
> maintained the use of this BH ever since.
>
> However, due to 9f939df955a4152aad69a19a77e0898631bb2c18, we schedule
> the BH via g_idle_add(), which is causing events to sometimes be
> delivered after we've already begun processing data from backends,
> leading to:
>
> known bugs:
>
> QMP:
> session negotation resets with OPENED event, in some cases this
> is causing new sessions to get sporadically reset
>
> potential bugs:
>
> hw/usb/redirect.c:
> can_read handler checks for dev->parser != NULL, which may be
> true if CLOSED BH has not been executed yet. In the past, OPENED
> quiesced outstanding CLOSED events prior to us reading client
> data. If it's delayed, our check may allow reads to occur even
> though we haven't processed the OPENED event yet, and when we
> do finally get the OPENED event, our state may get reset.
>
> qtest.c:
> can begin session before OPENED event is processed, leading to
> a spurious reset of the system and irq_levels
>
> gdbstub.c:
> may start a gdb session prior to the machine being paused
>
> 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 'explicit_be_open'
> 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.
>
> Reported-by: Stefan Priebe <s.pri...@profihost.ag>
> Cc: qemu-sta...@nongnu.org
> Signed-off-by: Michael Roth <mdr...@linux.vnet.ibm.com>
I don't know if the QMP queue is the ideal queue for this patch, but
I'd happily apply it if I get at least one Reviewed-by from the CC'ed
people.
> ---
> v3->v4:
> * renamed 'suppress_be_open_on_init' to 'explicit_be_open' to match
> existing 'explicit_fe_open' flag (Hans)
> * added missing 'explicit_be_open' flags for spice vmc/port and
> msmouse backends
>
> 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 --
> backends/msmouse.c | 1 +
> include/sysemu/char.h | 2 +-
> qemu-char.c | 38 +++++++++++++++++---------------------
> spice-qemu-char.c | 1 +
> ui/console.c | 1 -
> ui/gtk.c | 1 -
> 7 files changed, 20 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/backends/msmouse.c b/backends/msmouse.c
> index 0ac05a0..c0dbfcd 100644
> --- a/backends/msmouse.c
> +++ b/backends/msmouse.c
> @@ -70,6 +70,7 @@ CharDriverState *qemu_chr_open_msmouse(void)
> chr = g_malloc0(sizeof(CharDriverState));
> chr->chr_write = msmouse_chr_write;
> chr->chr_close = msmouse_chr_close;
> + chr->explicit_be_open = true;
>
> qemu_add_mouse_event_handler(msmouse_event, chr, 0, "QEMU Microsoft
> Mouse");
>
> diff --git a/include/sysemu/char.h b/include/sysemu/char.h
> index 5e42c90..066c216 100644
> --- a/include/sysemu/char.h
> +++ b/include/sysemu/char.h
> @@ -70,12 +70,12 @@ 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 explicit_be_open;
> int avail_connections;
> QemuOpts *opts;
> QTAILQ_ENTRY(CharDriverState) next;
> diff --git a/qemu-char.c b/qemu-char.c
> index d04b429..0b6ae95 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->explicit_be_open = 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->explicit_be_open = 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->explicit_be_open = 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->explicit_be_open = 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->explicit_be_open = 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->explicit_be_open) {
> + 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->explicit_be_open) {
> + qemu_chr_be_event(chr, CHR_EVENT_OPENED);
> + }
> QTAILQ_INSERT_TAIL(&chardevs, chr, next);
> return ret;
> } else {
> diff --git a/spice-qemu-char.c b/spice-qemu-char.c
> index f10970c..6d147a7 100644
> --- a/spice-qemu-char.c
> +++ b/spice-qemu-char.c
> @@ -255,6 +255,7 @@ static CharDriverState *chr_open(const char *subtype)
> chr->chr_add_watch = spice_chr_add_watch;
> chr->chr_close = spice_chr_close;
> chr->chr_set_fe_open = spice_chr_set_fe_open;
> + chr->explicit_be_open = true;
>
> QLIST_INSERT_HEAD(&spice_chars, s, next);
>
> 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 3bc2842..ef1bb71 100644
> --- a/ui/gtk.c
> +++ b/ui/gtk.c
> @@ -1216,7 +1216,6 @@ 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);
> }
