Re: [Qemu-devel] [PATCH v2] chardev: Use timer instead of bottom-half to postpone open event

[Aurelien Jarno <aurelien@aurel32.net>]

On Wed, Oct 31, 2012 at 02:23:15PM +0100, Jan Kiszka wrote:
> On 2012-10-12 09:52, Jan Kiszka wrote:
> > As the block layer may decide to flush bottom-halfs while the machine is
> > still initializing (e.g. to read geometry data from the disk), our
> > postponed open event may be processed before the last frontend
> > registered with a muxed chardev.
> > 
> > Until the semantics of BHs have been clarified, use an expired timer to
> > achieve the same effect (suggested by Paolo Bonzini). This requires to
> > perform the alarm timer initialization earlier as otherwise timer
> > subsystem can be used before being ready.
> > 
> > Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> > ---
> > 
> > Changes in v2:
> >  - Move init_alarm_timer call to fix e.g. -monitor stdio
> 
> Ping?
> 
> Jan
> 
> > 
> >  qemu-char.c |   13 +++++++------
> >  qemu-char.h |    2 +-
> >  vl.c        |   10 +++++-----
> >  3 files changed, 13 insertions(+), 12 deletions(-)
> > 
> > diff --git a/qemu-char.c b/qemu-char.c
> > index b082bae..d8eed21 100644
> > --- a/qemu-char.c
> > +++ b/qemu-char.c
> > @@ -123,19 +123,20 @@ void qemu_chr_be_event(CharDriverState *s, int event)
> >      s->chr_event(s->handler_opaque, event);
> >  }
> >  
> > -static void qemu_chr_generic_open_bh(void *opaque)
> > +static void qemu_chr_fire_open_event(void *opaque)
> >  {
> >      CharDriverState *s = opaque;
> >      qemu_chr_be_event(s, CHR_EVENT_OPENED);
> > -    qemu_bh_delete(s->bh);
> > -    s->bh = NULL;
> > +    qemu_free_timer(s->open_timer);
> > +    s->open_timer = NULL;
> >  }
> >  
> >  void qemu_chr_generic_open(CharDriverState *s)
> >  {
> > -    if (s->bh == NULL) {
> > -	s->bh = qemu_bh_new(qemu_chr_generic_open_bh, s);
> > -	qemu_bh_schedule(s->bh);
> > +    if (s->open_timer == NULL) {
> > +        s->open_timer = qemu_new_timer_ms(vm_clock,
> > +                                          qemu_chr_fire_open_event, s);
> > +        qemu_mod_timer(s->open_timer, qemu_get_clock_ms(vm_clock) - 1);
> >      }
> >  }
> >  
> > diff --git a/qemu-char.h b/qemu-char.h
> > index 486644b..297dd98 100644
> > --- a/qemu-char.h
> > +++ b/qemu-char.h
> > @@ -69,7 +69,7 @@ struct CharDriverState {
> >      void (*chr_guest_open)(struct CharDriverState *chr);
> >      void (*chr_guest_close)(struct CharDriverState *chr);
> >      void *opaque;
> > -    QEMUBH *bh;
> > +    QEMUTimer *open_timer;
> >      char *label;
> >      char *filename;
> >      int opened;
> > diff --git a/vl.c b/vl.c
> > index 5b357a3..586773c 100644
> > --- a/vl.c
> > +++ b/vl.c
> > @@ -3439,6 +3439,11 @@ int main(int argc, char **argv, char **envp)
> >              add_device_config(DEV_VIRTCON, "vc:80Cx24C");
> >      }
> >  
> > +    if (init_timer_alarm() < 0) {
> > +        fprintf(stderr, "could not initialize alarm timer\n");
> > +        exit(1);
> > +    }
> > +
> >      socket_init();
> >  
> >      if (qemu_opts_foreach(qemu_find_opts("chardev"), chardev_init_func, NULL, 1) != 0)
> > @@ -3506,11 +3511,6 @@ int main(int argc, char **argv, char **envp)
> >  
> >      os_set_line_buffering();
> >  
> > -    if (init_timer_alarm() < 0) {
> > -        fprintf(stderr, "could not initialize alarm timer\n");
> > -        exit(1);
> > -    }
> > -
> >  #ifdef CONFIG_SPICE
> >      /* spice needs the timers to be initialized by this point */
> >      qemu_spice_init();
> > 
> 
> 

Applied.

-- 
Aurelien Jarno	                        GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net