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

[Hans de Goede <hdegoede@redhat.com>]

Erm

This was supposed to be a reply to the "Re: [PATCH v2] usb-redir: Allow to attach USB 2.0 devices to 1.1 host controller"
thread, in that context is should make more sense :)

Regards,

Hans


On 10/08/2012 10:12 PM, Hans de Goede wrote:
> Hi,
>
> Funny that you ping about this just now, as I wanted to work on
> this today, but sofar I did not get around to it. Maybe tonight I will :)
>
> Long story short: Yes I've some remarks, but I pan to fix those myself and
> then merge it in my tree.
>
> I'll get back to you when this is done.
>
> Regards,
>
> Hans
>
>
> On 10/08/2012 07:07 PM, 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 <jan.kiszka@siemens.com>
>> ---
>>
>> 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;
>>