[Qemu-devel] [RFC PATCH V2] qemu-char: Fix context for g_source_attach()

[Qemu-devel] [RFC PATCH V2] qemu-char: Fix context for g_source_attach()

[Zhang Chen]

We want to poll and handle chardev in another thread
other than main loop. But qemu_chr_add_handlers() can only
work for global default context other than thread default context.
So we use g_source_attach(xx, g_main_context_get_thread_default())
replace g_source_attach(xx, NULL) to attach g_source.
Comments from jason.

Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 io/channel.c | 2 +-
 qemu-char.c  | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/io/channel.c b/io/channel.c
index 692eb17..cd25677 100644
--- a/io/channel.c
+++ b/io/channel.c
@@ -146,7 +146,7 @@ guint qio_channel_add_watch(QIOChannel *ioc,
 
     g_source_set_callback(source, (GSourceFunc)func, user_data, notify);
 
-    id = g_source_attach(source, NULL);
+    id = g_source_attach(source, g_main_context_get_thread_default());
     g_source_unref(source);
 
     return id;
diff --git a/qemu-char.c b/qemu-char.c
index 84f49ac..4340457 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -859,7 +859,7 @@ static gboolean io_watch_poll_prepare(GSource *source, gint *timeout_)
         iwp->src = qio_channel_create_watch(
             iwp->ioc, G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL);
         g_source_set_callback(iwp->src, iwp->fd_read, iwp->opaque, NULL);
-        g_source_attach(iwp->src, NULL);
+        g_source_attach(iwp->src, g_main_context_get_thread_default());
     } else {
         g_source_destroy(iwp->src);
         g_source_unref(iwp->src);
@@ -918,7 +918,7 @@ static guint io_add_watch_poll(QIOChannel *ioc,
     iwp->fd_read = (GSourceFunc) fd_read;
     iwp->src = NULL;
 
-    tag = g_source_attach(&iwp->parent, NULL);
+    tag = g_source_attach(&iwp->parent, g_main_context_get_thread_default());
     g_source_unref(&iwp->parent);
     return tag;
 }
@@ -3982,7 +3982,7 @@ int qemu_chr_fe_add_watch(CharDriverState *s, GIOCondition cond,
     }
 
     g_source_set_callback(src, (GSourceFunc)func, user_data, NULL);
-    tag = g_source_attach(src, NULL);
+    tag = g_source_attach(src, g_main_context_get_thread_default());
     g_source_unref(src);
 
     return tag;
-- 
2.7.4

Re: [Qemu-devel] [RFC PATCH V2] qemu-char: Fix context for g_source_attach()

[Zhang Chen]

On 06/22/2016 06:49 PM, Zhang Chen wrote:

Hi~ Paolo~

Just a ping...no news for a week~



> We want to poll and handle chardev in another thread
> other than main loop. But qemu_chr_add_handlers() can only
> work for global default context other than thread default context.
> So we use g_source_attach(xx, g_main_context_get_thread_default())
> replace g_source_attach(xx, NULL) to attach g_source.
> Comments from jason.
>
> Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>   io/channel.c | 2 +-
>   qemu-char.c  | 6 +++---
>   2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/io/channel.c b/io/channel.c
> index 692eb17..cd25677 100644
> --- a/io/channel.c
> +++ b/io/channel.c
> @@ -146,7 +146,7 @@ guint qio_channel_add_watch(QIOChannel *ioc,
>   
>       g_source_set_callback(source, (GSourceFunc)func, user_data, notify);
>   
> -    id = g_source_attach(source, NULL);
> +    id = g_source_attach(source, g_main_context_get_thread_default());
>       g_source_unref(source);
>   
>       return id;
> diff --git a/qemu-char.c b/qemu-char.c
> index 84f49ac..4340457 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -859,7 +859,7 @@ static gboolean io_watch_poll_prepare(GSource *source, gint *timeout_)
>           iwp->src = qio_channel_create_watch(
>               iwp->ioc, G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL);
>           g_source_set_callback(iwp->src, iwp->fd_read, iwp->opaque, NULL);
> -        g_source_attach(iwp->src, NULL);
> +        g_source_attach(iwp->src, g_main_context_get_thread_default());
>       } else {
>           g_source_destroy(iwp->src);
>           g_source_unref(iwp->src);
> @@ -918,7 +918,7 @@ static guint io_add_watch_poll(QIOChannel *ioc,
>       iwp->fd_read = (GSourceFunc) fd_read;
>       iwp->src = NULL;
>   
> -    tag = g_source_attach(&iwp->parent, NULL);
> +    tag = g_source_attach(&iwp->parent, g_main_context_get_thread_default());
>       g_source_unref(&iwp->parent);
>       return tag;
>   }
> @@ -3982,7 +3982,7 @@ int qemu_chr_fe_add_watch(CharDriverState *s, GIOCondition cond,
>       }
>   
>       g_source_set_callback(src, (GSourceFunc)func, user_data, NULL);
> -    tag = g_source_attach(src, NULL);
> +    tag = g_source_attach(src, g_main_context_get_thread_default());
>       g_source_unref(src);
>   
>       return tag;

-- 
Thanks
zhangchen

Re: [Qemu-devel] [RFC PATCH V2] qemu-char: Fix context for g_source_attach()

[Zhang Chen]

On 06/29/2016 02:46 PM, Zhang Chen wrote:
>
>
> On 06/22/2016 06:49 PM, Zhang Chen wrote:
>
> Hi~ Paolo~
>
> Just a ping...no news for a week~
>
>

Ping...again...

CC Fam
This patch about main loop.

Thanks
Zhang Chen

>
>> We want to poll and handle chardev in another thread
>> other than main loop. But qemu_chr_add_handlers() can only
>> work for global default context other than thread default context.
>> So we use g_source_attach(xx, g_main_context_get_thread_default())
>> replace g_source_attach(xx, NULL) to attach g_source.
>> Comments from jason.
>>
>> Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>> ---
>>   io/channel.c | 2 +-
>>   qemu-char.c  | 6 +++---
>>   2 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/io/channel.c b/io/channel.c
>> index 692eb17..cd25677 100644
>> --- a/io/channel.c
>> +++ b/io/channel.c
>> @@ -146,7 +146,7 @@ guint qio_channel_add_watch(QIOChannel *ioc,
>>         g_source_set_callback(source, (GSourceFunc)func, user_data, 
>> notify);
>>   -    id = g_source_attach(source, NULL);
>> +    id = g_source_attach(source, g_main_context_get_thread_default());
>>       g_source_unref(source);
>>         return id;
>> diff --git a/qemu-char.c b/qemu-char.c
>> index 84f49ac..4340457 100644
>> --- a/qemu-char.c
>> +++ b/qemu-char.c
>> @@ -859,7 +859,7 @@ static gboolean io_watch_poll_prepare(GSource 
>> *source, gint *timeout_)
>>           iwp->src = qio_channel_create_watch(
>>               iwp->ioc, G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL);
>>           g_source_set_callback(iwp->src, iwp->fd_read, iwp->opaque, 
>> NULL);
>> -        g_source_attach(iwp->src, NULL);
>> +        g_source_attach(iwp->src, g_main_context_get_thread_default());
>>       } else {
>>           g_source_destroy(iwp->src);
>>           g_source_unref(iwp->src);
>> @@ -918,7 +918,7 @@ static guint io_add_watch_poll(QIOChannel *ioc,
>>       iwp->fd_read = (GSourceFunc) fd_read;
>>       iwp->src = NULL;
>>   -    tag = g_source_attach(&iwp->parent, NULL);
>> +    tag = g_source_attach(&iwp->parent, 
>> g_main_context_get_thread_default());
>>       g_source_unref(&iwp->parent);
>>       return tag;
>>   }
>> @@ -3982,7 +3982,7 @@ int qemu_chr_fe_add_watch(CharDriverState *s, 
>> GIOCondition cond,
>>       }
>>         g_source_set_callback(src, (GSourceFunc)func, user_data, NULL);
>> -    tag = g_source_attach(src, NULL);
>> +    tag = g_source_attach(src, g_main_context_get_thread_default());
>>       g_source_unref(src);
>>         return tag;
>

-- 
Thanks
zhangchen

Re: [Qemu-devel] [RFC PATCH V2] qemu-char: Fix context for g_source_attach()

[Fam Zheng]

On Wed, 06/22 18:49, Zhang Chen wrote:
> We want to poll and handle chardev in another thread
> other than main loop. But qemu_chr_add_handlers() can only
> work for global default context other than thread default context.
> So we use g_source_attach(xx, g_main_context_get_thread_default())
> replace g_source_attach(xx, NULL) to attach g_source.
> Comments from jason.
> 
> Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  io/channel.c | 2 +-
>  qemu-char.c  | 6 +++---
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/io/channel.c b/io/channel.c
> index 692eb17..cd25677 100644
> --- a/io/channel.c
> +++ b/io/channel.c
> @@ -146,7 +146,7 @@ guint qio_channel_add_watch(QIOChannel *ioc,
>  
>      g_source_set_callback(source, (GSourceFunc)func, user_data, notify);
>  
> -    id = g_source_attach(source, NULL);
> +    id = g_source_attach(source, g_main_context_get_thread_default());
>      g_source_unref(source);
>  
>      return id;
> diff --git a/qemu-char.c b/qemu-char.c
> index 84f49ac..4340457 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -859,7 +859,7 @@ static gboolean io_watch_poll_prepare(GSource *source, gint *timeout_)
>          iwp->src = qio_channel_create_watch(
>              iwp->ioc, G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL);
>          g_source_set_callback(iwp->src, iwp->fd_read, iwp->opaque, NULL);
> -        g_source_attach(iwp->src, NULL);
> +        g_source_attach(iwp->src, g_main_context_get_thread_default());
>      } else {
>          g_source_destroy(iwp->src);
>          g_source_unref(iwp->src);
> @@ -918,7 +918,7 @@ static guint io_add_watch_poll(QIOChannel *ioc,
>      iwp->fd_read = (GSourceFunc) fd_read;
>      iwp->src = NULL;
>  
> -    tag = g_source_attach(&iwp->parent, NULL);
> +    tag = g_source_attach(&iwp->parent, g_main_context_get_thread_default());
>      g_source_unref(&iwp->parent);
>      return tag;
>  }
> @@ -3982,7 +3982,7 @@ int qemu_chr_fe_add_watch(CharDriverState *s, GIOCondition cond,
>      }
>  
>      g_source_set_callback(src, (GSourceFunc)func, user_data, NULL);
> -    tag = g_source_attach(src, NULL);
> +    tag = g_source_attach(src, g_main_context_get_thread_default());
>      g_source_unref(src);
>  
>      return tag;
> -- 

IIRC this opens a gate for your special thread (COLO compare thread?) to use
QIOChannel.

I think in the long run it is better to think about allowing integrating QIO to
AioContext, to support its usage outside main loop.  Given how opaque GSource
is, I'm not sure how feasible that is, or how useful it will be.  Anyway we
should definitely hear more opinions from Daniel and Paolo.

Fam

Re: [Qemu-devel] [RFC PATCH V2] qemu-char: Fix context for g_source_attach()

[Zhang Chen]

On 07/08/2016 09:48 AM, Fam Zheng wrote:
> On Wed, 06/22 18:49, Zhang Chen wrote:
>> We want to poll and handle chardev in another thread
>> other than main loop. But qemu_chr_add_handlers() can only
>> work for global default context other than thread default context.
>> So we use g_source_attach(xx, g_main_context_get_thread_default())
>> replace g_source_attach(xx, NULL) to attach g_source.
>> Comments from jason.
>>
>> Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>> ---
>>   io/channel.c | 2 +-
>>   qemu-char.c  | 6 +++---
>>   2 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/io/channel.c b/io/channel.c
>> index 692eb17..cd25677 100644
>> --- a/io/channel.c
>> +++ b/io/channel.c
>> @@ -146,7 +146,7 @@ guint qio_channel_add_watch(QIOChannel *ioc,
>>   
>>       g_source_set_callback(source, (GSourceFunc)func, user_data, notify);
>>   
>> -    id = g_source_attach(source, NULL);
>> +    id = g_source_attach(source, g_main_context_get_thread_default());
>>       g_source_unref(source);
>>   
>>       return id;
>> diff --git a/qemu-char.c b/qemu-char.c
>> index 84f49ac..4340457 100644
>> --- a/qemu-char.c
>> +++ b/qemu-char.c
>> @@ -859,7 +859,7 @@ static gboolean io_watch_poll_prepare(GSource *source, gint *timeout_)
>>           iwp->src = qio_channel_create_watch(
>>               iwp->ioc, G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL);
>>           g_source_set_callback(iwp->src, iwp->fd_read, iwp->opaque, NULL);
>> -        g_source_attach(iwp->src, NULL);
>> +        g_source_attach(iwp->src, g_main_context_get_thread_default());
>>       } else {
>>           g_source_destroy(iwp->src);
>>           g_source_unref(iwp->src);
>> @@ -918,7 +918,7 @@ static guint io_add_watch_poll(QIOChannel *ioc,
>>       iwp->fd_read = (GSourceFunc) fd_read;
>>       iwp->src = NULL;
>>   
>> -    tag = g_source_attach(&iwp->parent, NULL);
>> +    tag = g_source_attach(&iwp->parent, g_main_context_get_thread_default());
>>       g_source_unref(&iwp->parent);
>>       return tag;
>>   }
>> @@ -3982,7 +3982,7 @@ int qemu_chr_fe_add_watch(CharDriverState *s, GIOCondition cond,
>>       }
>>   
>>       g_source_set_callback(src, (GSourceFunc)func, user_data, NULL);
>> -    tag = g_source_attach(src, NULL);
>> +    tag = g_source_attach(src, g_main_context_get_thread_default());
>>       g_source_unref(src);
>>   
>>       return tag;
>> -- 
> IIRC this opens a gate for your special thread (COLO compare thread?) to use
> QIOChannel.

Yes,you are right.

>
> I think in the long run it is better to think about allowing integrating QIO to
> AioContext, to support its usage outside main loop.  Given how opaque GSource
> is, I'm not sure how feasible that is, or how useful it will be.  Anyway we
> should definitely hear more opinions from Daniel and Paolo.

I have test it. COLO compare thread(include qemu_chr_add_handlers())
works good after apply this patch.

We do this job in this way:
In net/colo-compare.c

static void *colo_compare_thread(void *opaque)
{
     GMainContext *worker_context;
     GMainLoop *compare_loop;
     CompareState *s = opaque;

     worker_context = g_main_context_new();
     g_assert(g_main_context_get_thread_default() == NULL);
     g_main_context_push_thread_default(worker_context);
     g_assert(g_main_context_get_thread_default() == worker_context);

     qemu_chr_add_handlers(s->chr_pri_in, compare_chr_can_read,
                           compare_pri_chr_in, NULL, s);
     qemu_chr_add_handlers(s->chr_sec_in, compare_chr_can_read,
                           compare_sec_chr_in, NULL, s);

     compare_loop = g_main_loop_new(worker_context, FALSE);

     g_main_loop_run(compare_loop);
......
}


Thanks
Zhang Chen


> Fam
>
>
> .
>

-- 
Thanks
zhangchen

Re: [Qemu-devel] [RFC PATCH V2] qemu-char: Fix context for g_source_attach()

[Daniel P. Berrange]

On Fri, Jul 08, 2016 at 09:48:23AM +0800, Fam Zheng wrote:
> On Wed, 06/22 18:49, Zhang Chen wrote:
> > We want to poll and handle chardev in another thread
> > other than main loop. But qemu_chr_add_handlers() can only
> > work for global default context other than thread default context.
> > So we use g_source_attach(xx, g_main_context_get_thread_default())
> > replace g_source_attach(xx, NULL) to attach g_source.
> > Comments from jason.
> > 
> > Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
> > Signed-off-by: Jason Wang <jasowang@redhat.com>
> > ---
> >  io/channel.c | 2 +-
> >  qemu-char.c  | 6 +++---
> >  2 files changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/io/channel.c b/io/channel.c
> > index 692eb17..cd25677 100644
> > --- a/io/channel.c
> > +++ b/io/channel.c
> > @@ -146,7 +146,7 @@ guint qio_channel_add_watch(QIOChannel *ioc,
> >  
> >      g_source_set_callback(source, (GSourceFunc)func, user_data, notify);
> >  
> > -    id = g_source_attach(source, NULL);
> > +    id = g_source_attach(source, g_main_context_get_thread_default());
> >      g_source_unref(source);
> >  
> >      return id;
> > diff --git a/qemu-char.c b/qemu-char.c
> > index 84f49ac..4340457 100644
> > --- a/qemu-char.c
> > +++ b/qemu-char.c
> > @@ -859,7 +859,7 @@ static gboolean io_watch_poll_prepare(GSource *source, gint *timeout_)
> >          iwp->src = qio_channel_create_watch(
> >              iwp->ioc, G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL);
> >          g_source_set_callback(iwp->src, iwp->fd_read, iwp->opaque, NULL);
> > -        g_source_attach(iwp->src, NULL);
> > +        g_source_attach(iwp->src, g_main_context_get_thread_default());
> >      } else {
> >          g_source_destroy(iwp->src);
> >          g_source_unref(iwp->src);
> > @@ -918,7 +918,7 @@ static guint io_add_watch_poll(QIOChannel *ioc,
> >      iwp->fd_read = (GSourceFunc) fd_read;
> >      iwp->src = NULL;
> >  
> > -    tag = g_source_attach(&iwp->parent, NULL);
> > +    tag = g_source_attach(&iwp->parent, g_main_context_get_thread_default());
> >      g_source_unref(&iwp->parent);
> >      return tag;
> >  }
> > @@ -3982,7 +3982,7 @@ int qemu_chr_fe_add_watch(CharDriverState *s, GIOCondition cond,
> >      }
> >  
> >      g_source_set_callback(src, (GSourceFunc)func, user_data, NULL);
> > -    tag = g_source_attach(src, NULL);
> > +    tag = g_source_attach(src, g_main_context_get_thread_default());
> >      g_source_unref(src);
> >  
> >      return tag;
> > -- 
> 
> IIRC this opens a gate for your special thread (COLO compare thread?) to use
> QIOChannel.

I've no real objection to this proposed patch, though it is fairly pointless
to take it now without seeing any following patch that actually makes use
of this added feature.

> I think in the long run it is better to think about allowing integrating QIO to
> AioContext, to support its usage outside main loop.  Given how opaque GSource
> is, I'm not sure how feasible that is, or how useful it will be.  Anyway we
> should definitely hear more opinions from Daniel and Paolo.

Personally I think it is preferable to stick as close to the standard GSource
model as possible, as that's widely used & well understood API, compared to the
QEMU specific AioContext.

Regards,
Daniel
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Re: [Qemu-devel] [RFC PATCH V2] qemu-char: Fix context for g_source_attach()

[Paolo Bonzini]

On 08/07/2016 10:54, Daniel P. Berrange wrote:
> On Fri, Jul 08, 2016 at 09:48:23AM +0800, Fam Zheng wrote:
>> On Wed, 06/22 18:49, Zhang Chen wrote:
>>> We want to poll and handle chardev in another thread
>>> other than main loop. But qemu_chr_add_handlers() can only
>>> work for global default context other than thread default context.
>>> So we use g_source_attach(xx, g_main_context_get_thread_default())
>>> replace g_source_attach(xx, NULL) to attach g_source.
>>> Comments from jason.
>>>
>>> Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>>> ---
>>>  io/channel.c | 2 +-
>>>  qemu-char.c  | 6 +++---
>>>  2 files changed, 4 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/io/channel.c b/io/channel.c
>>> index 692eb17..cd25677 100644
>>> --- a/io/channel.c
>>> +++ b/io/channel.c
>>> @@ -146,7 +146,7 @@ guint qio_channel_add_watch(QIOChannel *ioc,
>>>  
>>>      g_source_set_callback(source, (GSourceFunc)func, user_data, notify);
>>>  
>>> -    id = g_source_attach(source, NULL);
>>> +    id = g_source_attach(source, g_main_context_get_thread_default());
>>>      g_source_unref(source);
>>>  
>>>      return id;
>>> diff --git a/qemu-char.c b/qemu-char.c
>>> index 84f49ac..4340457 100644
>>> --- a/qemu-char.c
>>> +++ b/qemu-char.c
>>> @@ -859,7 +859,7 @@ static gboolean io_watch_poll_prepare(GSource *source, gint *timeout_)
>>>          iwp->src = qio_channel_create_watch(
>>>              iwp->ioc, G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL);
>>>          g_source_set_callback(iwp->src, iwp->fd_read, iwp->opaque, NULL);
>>> -        g_source_attach(iwp->src, NULL);
>>> +        g_source_attach(iwp->src, g_main_context_get_thread_default());
>>>      } else {
>>>          g_source_destroy(iwp->src);
>>>          g_source_unref(iwp->src);
>>> @@ -918,7 +918,7 @@ static guint io_add_watch_poll(QIOChannel *ioc,
>>>      iwp->fd_read = (GSourceFunc) fd_read;
>>>      iwp->src = NULL;
>>>  
>>> -    tag = g_source_attach(&iwp->parent, NULL);
>>> +    tag = g_source_attach(&iwp->parent, g_main_context_get_thread_default());
>>>      g_source_unref(&iwp->parent);
>>>      return tag;
>>>  }
>>> @@ -3982,7 +3982,7 @@ int qemu_chr_fe_add_watch(CharDriverState *s, GIOCondition cond,
>>>      }
>>>  
>>>      g_source_set_callback(src, (GSourceFunc)func, user_data, NULL);
>>> -    tag = g_source_attach(src, NULL);
>>> +    tag = g_source_attach(src, g_main_context_get_thread_default());
>>>      g_source_unref(src);
>>>  
>>>      return tag;
>>> -- 
>>
>> IIRC this opens a gate for your special thread (COLO compare thread?) to use
>> QIOChannel.
> 
> I've no real objection to this proposed patch, though it is fairly pointless
> to take it now without seeing any following patch that actually makes use
> of this added feature.

I agree.

>> I think in the long run it is better to think about allowing integrating QIO to
>> AioContext, to support its usage outside main loop.  Given how opaque GSource
>> is, I'm not sure how feasible that is, or how useful it will be.  Anyway we
>> should definitely hear more opinions from Daniel and Paolo.
> 
> Personally I think it is preferable to stick as close to the standard GSource
> model as possible, as that's widely used & well understood API, compared to the
> QEMU specific AioContext.

AioContext is more optimized for the case where the callbacks are
static.  In general this is not the case for qemu-char.c.

Paolo

Re: [Qemu-devel] [RFC PATCH V2] qemu-char: Fix context for g_source_attach()

[Zhang Chen]

On 07/08/2016 10:27 PM, Paolo Bonzini wrote:
>
> On 08/07/2016 10:54, Daniel P. Berrange wrote:
>> On Fri, Jul 08, 2016 at 09:48:23AM +0800, Fam Zheng wrote:
>>> On Wed, 06/22 18:49, Zhang Chen wrote:
>>>> We want to poll and handle chardev in another thread
>>>> other than main loop. But qemu_chr_add_handlers() can only
>>>> work for global default context other than thread default context.
>>>> So we use g_source_attach(xx, g_main_context_get_thread_default())
>>>> replace g_source_attach(xx, NULL) to attach g_source.
>>>> Comments from jason.
>>>>
>>>> Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
>>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>>>> ---
>>>>   io/channel.c | 2 +-
>>>>   qemu-char.c  | 6 +++---
>>>>   2 files changed, 4 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/io/channel.c b/io/channel.c
>>>> index 692eb17..cd25677 100644
>>>> --- a/io/channel.c
>>>> +++ b/io/channel.c
>>>> @@ -146,7 +146,7 @@ guint qio_channel_add_watch(QIOChannel *ioc,
>>>>   
>>>>       g_source_set_callback(source, (GSourceFunc)func, user_data, notify);
>>>>   
>>>> -    id = g_source_attach(source, NULL);
>>>> +    id = g_source_attach(source, g_main_context_get_thread_default());
>>>>       g_source_unref(source);
>>>>   
>>>>       return id;
>>>> diff --git a/qemu-char.c b/qemu-char.c
>>>> index 84f49ac..4340457 100644
>>>> --- a/qemu-char.c
>>>> +++ b/qemu-char.c
>>>> @@ -859,7 +859,7 @@ static gboolean io_watch_poll_prepare(GSource *source, gint *timeout_)
>>>>           iwp->src = qio_channel_create_watch(
>>>>               iwp->ioc, G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL);
>>>>           g_source_set_callback(iwp->src, iwp->fd_read, iwp->opaque, NULL);
>>>> -        g_source_attach(iwp->src, NULL);
>>>> +        g_source_attach(iwp->src, g_main_context_get_thread_default());
>>>>       } else {
>>>>           g_source_destroy(iwp->src);
>>>>           g_source_unref(iwp->src);
>>>> @@ -918,7 +918,7 @@ static guint io_add_watch_poll(QIOChannel *ioc,
>>>>       iwp->fd_read = (GSourceFunc) fd_read;
>>>>       iwp->src = NULL;
>>>>   
>>>> -    tag = g_source_attach(&iwp->parent, NULL);
>>>> +    tag = g_source_attach(&iwp->parent, g_main_context_get_thread_default());
>>>>       g_source_unref(&iwp->parent);
>>>>       return tag;
>>>>   }
>>>> @@ -3982,7 +3982,7 @@ int qemu_chr_fe_add_watch(CharDriverState *s, GIOCondition cond,
>>>>       }
>>>>   
>>>>       g_source_set_callback(src, (GSourceFunc)func, user_data, NULL);
>>>> -    tag = g_source_attach(src, NULL);
>>>> +    tag = g_source_attach(src, g_main_context_get_thread_default());
>>>>       g_source_unref(src);
>>>>   
>>>>       return tag;
>>>> -- 
>>> IIRC this opens a gate for your special thread (COLO compare thread?) to use
>>> QIOChannel.
>> I've no real objection to this proposed patch, though it is fairly pointless
>> to take it now without seeing any following patch that actually makes use
>> of this added feature.
> I agree.

Should I move this patch to the "[RFC PATCH V5 0/4] Introduce COLO-compare"
patch set? that can show how it works.

you can see this patch for how to use:
http://lists.nongnu.org/archive/html/qemu-devel/2016-06/msg06754.html


>
>>> I think in the long run it is better to think about allowing integrating QIO to
>>> AioContext, to support its usage outside main loop.  Given how opaque GSource
>>> is, I'm not sure how feasible that is, or how useful it will be.  Anyway we
>>> should definitely hear more opinions from Daniel and Paolo.
>> Personally I think it is preferable to stick as close to the standard GSource
>> model as possible, as that's widely used & well understood API, compared to the
>> QEMU specific AioContext.
> AioContext is more optimized for the case where the callbacks are
> static.  In general this is not the case for qemu-char.c.

I don't sure AioContext can do this job good, but I think
we can make qemu more flexible to do same one job.
All roads lead to Rome.

Thanks
Zhang Chen


> Paolo
>
>
> .
>

-- 
Thanks
zhangchen

Re: [Qemu-devel] [RFC PATCH V2] qemu-char: Fix context for g_source_attach()

[Zhang Chen]

Hi~ All~~

Can you give me some feedback for this patch?

We need more comments~~

COLO project depend on this patch to work.

Because this patch colo-compare can make handler of qemu_chr_add_handlers()

run in compare thread, reduce workload of main_loop in network busy 
situation.

This idea from Jason.


Thanks
Zhang Chen




On 07/11/2016 10:12 AM, Zhang Chen wrote:
>
>
> On 07/08/2016 10:27 PM, Paolo Bonzini wrote:
>>
>> On 08/07/2016 10:54, Daniel P. Berrange wrote:
>>> On Fri, Jul 08, 2016 at 09:48:23AM +0800, Fam Zheng wrote:
>>>> On Wed, 06/22 18:49, Zhang Chen wrote:
>>>>> We want to poll and handle chardev in another thread
>>>>> other than main loop. But qemu_chr_add_handlers() can only
>>>>> work for global default context other than thread default context.
>>>>> So we use g_source_attach(xx, g_main_context_get_thread_default())
>>>>> replace g_source_attach(xx, NULL) to attach g_source.
>>>>> Comments from jason.
>>>>>
>>>>> Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
>>>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>>>>> ---
>>>>>   io/channel.c | 2 +-
>>>>>   qemu-char.c  | 6 +++---
>>>>>   2 files changed, 4 insertions(+), 4 deletions(-)
>>>>>
>>>>> diff --git a/io/channel.c b/io/channel.c
>>>>> index 692eb17..cd25677 100644
>>>>> --- a/io/channel.c
>>>>> +++ b/io/channel.c
>>>>> @@ -146,7 +146,7 @@ guint qio_channel_add_watch(QIOChannel *ioc,
>>>>>         g_source_set_callback(source, (GSourceFunc)func, 
>>>>> user_data, notify);
>>>>>   -    id = g_source_attach(source, NULL);
>>>>> +    id = g_source_attach(source, 
>>>>> g_main_context_get_thread_default());
>>>>>       g_source_unref(source);
>>>>>         return id;
>>>>> diff --git a/qemu-char.c b/qemu-char.c
>>>>> index 84f49ac..4340457 100644
>>>>> --- a/qemu-char.c
>>>>> +++ b/qemu-char.c
>>>>> @@ -859,7 +859,7 @@ static gboolean io_watch_poll_prepare(GSource 
>>>>> *source, gint *timeout_)
>>>>>           iwp->src = qio_channel_create_watch(
>>>>>               iwp->ioc, G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL);
>>>>>           g_source_set_callback(iwp->src, iwp->fd_read, 
>>>>> iwp->opaque, NULL);
>>>>> -        g_source_attach(iwp->src, NULL);
>>>>> +        g_source_attach(iwp->src, 
>>>>> g_main_context_get_thread_default());
>>>>>       } else {
>>>>>           g_source_destroy(iwp->src);
>>>>>           g_source_unref(iwp->src);
>>>>> @@ -918,7 +918,7 @@ static guint io_add_watch_poll(QIOChannel *ioc,
>>>>>       iwp->fd_read = (GSourceFunc) fd_read;
>>>>>       iwp->src = NULL;
>>>>>   -    tag = g_source_attach(&iwp->parent, NULL);
>>>>> +    tag = g_source_attach(&iwp->parent, 
>>>>> g_main_context_get_thread_default());
>>>>>       g_source_unref(&iwp->parent);
>>>>>       return tag;
>>>>>   }
>>>>> @@ -3982,7 +3982,7 @@ int qemu_chr_fe_add_watch(CharDriverState 
>>>>> *s, GIOCondition cond,
>>>>>       }
>>>>>         g_source_set_callback(src, (GSourceFunc)func, user_data, 
>>>>> NULL);
>>>>> -    tag = g_source_attach(src, NULL);
>>>>> +    tag = g_source_attach(src, g_main_context_get_thread_default());
>>>>>       g_source_unref(src);
>>>>>         return tag;
>>>>> -- 
>>>> IIRC this opens a gate for your special thread (COLO compare 
>>>> thread?) to use
>>>> QIOChannel.
>>> I've no real objection to this proposed patch, though it is fairly 
>>> pointless
>>> to take it now without seeing any following patch that actually 
>>> makes use
>>> of this added feature.
>> I agree.
>
> Should I move this patch to the "[RFC PATCH V5 0/4] Introduce 
> COLO-compare"
> patch set? that can show how it works.
>
> you can see this patch for how to use:
> http://lists.nongnu.org/archive/html/qemu-devel/2016-06/msg06754.html
>
>

In colo_compare_thread()


>>
>>>> I think in the long run it is better to think about allowing 
>>>> integrating QIO to
>>>> AioContext, to support its usage outside main loop.  Given how 
>>>> opaque GSource
>>>> is, I'm not sure how feasible that is, or how useful it will be.  
>>>> Anyway we
>>>> should definitely hear more opinions from Daniel and Paolo.
>>> Personally I think it is preferable to stick as close to the 
>>> standard GSource
>>> model as possible, as that's widely used & well understood API, 
>>> compared to the
>>> QEMU specific AioContext.
>> AioContext is more optimized for the case where the callbacks are
>> static.  In general this is not the case for qemu-char.c.
>
> I don't sure AioContext can do this job good, but I think
> we can make qemu more flexible to do same one job.
> All roads lead to Rome.
>
> Thanks
> Zhang Chen
>
>
>> Paolo
>>
>>
>> .
>>
>

-- 
Thanks
zhangchen

Re: [Qemu-devel] [RFC PATCH V2] qemu-char: Fix context for g_source_attach()

[Jason Wang]

On 2016年07月18日 09:55, Zhang Chen wrote:
> Hi~ All~~
>
> Can you give me some feedback for this patch?
>
> We need more comments~~
>
> COLO project depend on this patch to work.
>
> Because this patch colo-compare can make handler of 
> qemu_chr_add_handlers()
>
> run in compare thread, reduce workload of main_loop in network busy 
> situation.
>
> This idea from Jason.
>
>
> Thanks
> Zhang Chen

I think you can put this patch in the series of COLO comparing thread 
which shows its using. And then you can ask acked-by or reviewed-by from 
other maintainers.

Thanks

Re: [Qemu-devel] [RFC PATCH V2] qemu-char: Fix context for g_source_attach()

[Zhang Chen]

On 07/18/2016 01:31 PM, Jason Wang wrote:
>
>
> On 2016年07月18日 09:55, Zhang Chen wrote:
>> Hi~ All~~
>>
>> Can you give me some feedback for this patch?
>>
>> We need more comments~~
>>
>> COLO project depend on this patch to work.
>>
>> Because this patch colo-compare can make handler of 
>> qemu_chr_add_handlers()
>>
>> run in compare thread, reduce workload of main_loop in network busy 
>> situation.
>>
>> This idea from Jason.
>>
>>
>> Thanks
>> Zhang Chen
>
> I think you can put this patch in the series of COLO comparing thread 
> which shows its using. And then you can ask acked-by or reviewed-by 
> from other maintainers.
>
> Thanks
>
>

Make sense. I will add this patch in next colo-compare series.

Thanks
Zhang Chen

>
>

-- 
Thanks
zhangchen