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

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

[Jan Kiszka]

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;
-- 
1.7.3.4

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 <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;

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

Tested-by: Aurelien Jarno <aurelien@aurel32.net>


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

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

[Hans de Goede]

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;
>

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

[Hans de Goede]

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;
>>

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

[Jan Kiszka]

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

 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();
-- 
1.7.3.4

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

[Jan Kiszka]

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();
> 


-- 
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux

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

[Aurelien Jarno]

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