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

[Aurelien Jarno]

On Mon, Oct 08, 2012 at 07:07:08PM +0200, 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).
> 
> Signed-off-by: Jan Kiszka <address@hidden>
> ---
> 
> This obsoletes the versatilepb hack.
> 
>  qemu-char.c |   13 +++++++------
>  qemu-char.h |    2 +-
>  2 files changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/qemu-char.c b/qemu-char.c
> index f9ee2f0..fb4e3dc 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;

It works for me on both MIPS malta and ARM versatile. Thanks.

Tested-by: Aurelien Jarno <address@hidden>


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