[Qemu-devel] [PATCH v3 0/3] chardev: convert leftover glib APIs to use dedicate gcontext

[Qemu-devel] [PATCH v3 0/3] chardev: convert leftover glib APIs to use dedicate gcontext

[Peter Xu]

v3:
- rename function to qemu_chr_timeout_add_ms() [Stefan]
- add comment on return code [Stefan]
- add comment in commit message on why change GSource name [Stefan]

v2:
- add r-bs
- fix patch 3 on some s->ms conversion [Marc-André]

There were existing work that tried to allow chardev to be run in a
dedicated gcontext rather than the default main context/thread.
Basically that work passed in the correct gcontext during
g_source_attach().  However, I found something missing along the way,
that some legacy glib APIs are used by chardev code which take the
main context as default:

   g_timeout_add_seconds
   g_timeout_add
   g_idle_add

To fully allow the chardevs to be run in dedicated gcontext, we need
to convert all these legacy APIs into g_source_attach() calls as well,
with the correct gcontext passed in.

This series tries to clean the rest of things up.

I picked up patch 1 from monitor-oob series into this series (which is
a missing of chardev frontend call fix for g_source_attach()), so that
this series can be a complete fix.

Please review.  Thanks,

Peter Xu (3):
  chardev: use backend chr context when watch for fe
  chardev: let g_idle_add() be with chardev gcontext
  chardev: introduce qemu_chr_timeout_add_ms()

 chardev/char-fe.c      |  2 +-
 chardev/char-pty.c     | 16 ++++++++--------
 chardev/char-socket.c  |  6 ++++--
 chardev/char.c         | 21 +++++++++++++++++++++
 hw/char/terminal3270.c |  7 ++++---
 include/chardev/char.h |  3 +++
 6 files changed, 41 insertions(+), 14 deletions(-)

-- 
2.14.3

[Qemu-devel] [PATCH v3 1/3] chardev: use backend chr context when watch for fe

[Peter Xu]

In commit 6bbb6c0644 ("chardev: use per-dev context for
io_add_watch_poll", 2017-09-22) all the chardev watches are converted to
use per-chardev gcontext to support chardev to be run outside default
main thread.  However that's still missing one call from the frontend
code.  Touch that up.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 chardev/char-fe.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/chardev/char-fe.c b/chardev/char-fe.c
index ee6d596100..c611b3fa3e 100644
--- a/chardev/char-fe.c
+++ b/chardev/char-fe.c
@@ -356,7 +356,7 @@ guint qemu_chr_fe_add_watch(CharBackend *be, GIOCondition cond,
     }
 
     g_source_set_callback(src, (GSourceFunc)func, user_data, NULL);
-    tag = g_source_attach(src, NULL);
+    tag = g_source_attach(src, s->gcontext);
     g_source_unref(src);
 
     return tag;
-- 
2.14.3

[Qemu-devel] [PATCH v3 2/3] chardev: let g_idle_add() be with chardev gcontext

[Peter Xu]

The idle task will be attached to main gcontext even if the chardev
backend is running in another gcontext.  Fix the only caller by
extending the g_idle_add() logic into the more powerful
g_source_attach().  It's basically g_idle_add_full() implementation, but
with the chardev's gcontext passed in.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 chardev/char-pty.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/chardev/char-pty.c b/chardev/char-pty.c
index 761ae6dec1..dd17b1b823 100644
--- a/chardev/char-pty.c
+++ b/chardev/char-pty.c
@@ -210,9 +210,14 @@ static void pty_chr_state(Chardev *chr, int connected)
             s->timer_tag = 0;
         }
         if (!s->connected) {
+            GSource *source = g_idle_source_new();
+
             g_assert(s->open_tag == 0);
             s->connected = 1;
-            s->open_tag = g_idle_add(qemu_chr_be_generic_open_func, chr);
+            g_source_set_callback(source, qemu_chr_be_generic_open_func,
+                                  chr, NULL);
+            s->open_tag = g_source_attach(source, chr->gcontext);
+            g_source_unref(source);
         }
         if (!chr->gsource) {
             chr->gsource = io_add_watch_poll(chr, s->ioc,
-- 
2.14.3

[Qemu-devel] [PATCH v3 3/3] chardev: introduce qemu_chr_timeout_add_ms()

[Peter Xu]

It's a replacement of g_timeout_add[_seconds]() for chardevs.  Chardevs
now can have dedicated gcontext, we should always bind chardev tasks
onto those gcontext rather than the default main context.  Since there
are quite a few of g_timeout_add[_seconds]() callers, a new function
qemu_chr_timeout_add_ms() is introduced.

One thing to mention is that, terminal3270 is still always running on
main gcontext.  However let's convert that as well since it's still part
of chardev codes and in case one day we'll miss that when we move it out
of main gcontext too.

Also, in pty_chr_rearm_timer() the GSource name is not user visible, and
does not really matter much.  Unify the two calls into one.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 chardev/char-pty.c     |  9 ++-------
 chardev/char-socket.c  |  6 ++++--
 chardev/char.c         | 21 +++++++++++++++++++++
 hw/char/terminal3270.c |  7 ++++---
 include/chardev/char.h |  3 +++
 5 files changed, 34 insertions(+), 12 deletions(-)

diff --git a/chardev/char-pty.c b/chardev/char-pty.c
index dd17b1b823..2b37ad55ed 100644
--- a/chardev/char-pty.c
+++ b/chardev/char-pty.c
@@ -78,13 +78,8 @@ static void pty_chr_rearm_timer(Chardev *chr, int ms)
         s->timer_tag = 0;
     }
 
-    if (ms == 1000) {
-        name = g_strdup_printf("pty-timer-secs-%s", chr->label);
-        s->timer_tag = g_timeout_add_seconds(1, pty_chr_timer, chr);
-    } else {
-        name = g_strdup_printf("pty-timer-ms-%s", chr->label);
-        s->timer_tag = g_timeout_add(ms, pty_chr_timer, chr);
-    }
+    name = g_strdup_printf("pty-timer-ms-%s", chr->label);
+    s->timer_tag = qemu_chr_timeout_add_ms(chr, ms, pty_chr_timer, chr);
     g_source_set_name_by_id(s->timer_tag, name);
     g_free(name);
 }
diff --git a/chardev/char-socket.c b/chardev/char-socket.c
index 630a7f2995..9527314708 100644
--- a/chardev/char-socket.c
+++ b/chardev/char-socket.c
@@ -73,8 +73,10 @@ static void qemu_chr_socket_restart_timer(Chardev *chr)
     char *name;
 
     assert(s->connected == 0);
-    s->reconnect_timer = g_timeout_add_seconds(s->reconnect_time,
-                                               socket_reconnect_timeout, chr);
+    s->reconnect_timer = qemu_chr_timeout_add_ms(chr,
+                                                 s->reconnect_time * 1000,
+                                                 socket_reconnect_timeout,
+                                                 chr);
     name = g_strdup_printf("chardev-socket-reconnect-%s", chr->label);
     g_source_set_name_by_id(s->reconnect_timer, name);
     g_free(name);
diff --git a/chardev/char.c b/chardev/char.c
index 8c3765ee99..d77787d67a 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -1084,6 +1084,27 @@ void qmp_chardev_send_break(const char *id, Error **errp)
     qemu_chr_be_event(chr, CHR_EVENT_BREAK);
 }
 
+/*
+ * Add a timeout callback for the chardev (in milliseconds). Please
+ * use this to add timeout hook for chardev instead of g_timeout_add()
+ * and g_timeout_add_seconds(), to make sure the gcontext that the
+ * task bound to is correct.  Returns the ID of the timeout GSource in
+ * gcontext of the chardev.
+ */
+guint qemu_chr_timeout_add_ms(Chardev *chr, guint ms, GSourceFunc func,
+                              void *private)
+{
+    GSource *source = g_timeout_source_new(ms);
+    guint id;
+
+    assert(func);
+    g_source_set_callback(source, func, private, NULL);
+    id = g_source_attach(source, chr->gcontext);
+    g_source_unref(source);
+
+    return id;
+}
+
 void qemu_chr_cleanup(void)
 {
     object_unparent(get_chardevs_root());
diff --git a/hw/char/terminal3270.c b/hw/char/terminal3270.c
index a109ce5987..b0f81d0d16 100644
--- a/hw/char/terminal3270.c
+++ b/hw/char/terminal3270.c
@@ -94,8 +94,8 @@ static void terminal_read(void *opaque, const uint8_t *buf, int size)
         g_source_remove(t->timer_tag);
         t->timer_tag = 0;
     }
-    t->timer_tag = g_timeout_add_seconds(600, send_timing_mark_cb, t);
-
+    t->timer_tag = qemu_chr_timeout_add_ms(t->chr.chr, 600 * 1000,
+                                           send_timing_mark_cb, t);
     memcpy(&t->inv[t->in_len], buf, size);
     t->in_len += size;
     if (t->in_len < 2) {
@@ -157,7 +157,8 @@ static void chr_event(void *opaque, int event)
          * char-socket.c. Once qemu receives the terminal-type of the
          * client, mark handshake done and trigger everything rolling again.
          */
-        t->timer_tag = g_timeout_add_seconds(600, send_timing_mark_cb, t);
+        t->timer_tag = qemu_chr_timeout_add_ms(t->chr.chr, 600 * 1000,
+                                               send_timing_mark_cb, t);
         break;
     case CHR_EVENT_CLOSED:
         sch->curr_status.scsw.dstat = SCSW_DSTAT_DEVICE_END;
diff --git a/include/chardev/char.h b/include/chardev/char.h
index 778d610295..f1b67af4d2 100644
--- a/include/chardev/char.h
+++ b/include/chardev/char.h
@@ -256,6 +256,9 @@ Chardev *qemu_chardev_new(const char *id, const char *typename,
 
 extern int term_escape_char;
 
+guint qemu_chr_timeout_add_ms(Chardev *chr, guint ms, GSourceFunc func,
+                              void *private);
+
 /* console.c */
 void qemu_chr_parse_vc(QemuOpts *opts, ChardevBackend *backend, Error **errp);
 
-- 
2.14.3

Re: [Qemu-devel] [PATCH v3 0/3] chardev: convert leftover glib APIs to use dedicate gcontext

[Peter Xu]

On Thu, Jan 04, 2018 at 06:43:33PM +0800, Peter Xu wrote:
> v3:
> - rename function to qemu_chr_timeout_add_ms() [Stefan]
> - add comment on return code [Stefan]
> - add comment in commit message on why change GSource name [Stefan]
> 
> v2:
> - add r-bs
> - fix patch 3 on some s->ms conversion [Marc-André]
> 
> There were existing work that tried to allow chardev to be run in a
> dedicated gcontext rather than the default main context/thread.
> Basically that work passed in the correct gcontext during
> g_source_attach().  However, I found something missing along the way,
> that some legacy glib APIs are used by chardev code which take the
> main context as default:
> 
>    g_timeout_add_seconds
>    g_timeout_add
>    g_idle_add

Self NAK.

I just noticed something more critical: these calls are still managing
gsources using IDs rather than GSource objects.  That should not work,
especially if we want to remove these events using g_source_remove().
That can be fairly dangerous after OOB series merged.  I need to use
GSource objects to replace the tag IDs.

I'll prepare another version tomorrow.  Sorry for the troublesome.

> 
> To fully allow the chardevs to be run in dedicated gcontext, we need
> to convert all these legacy APIs into g_source_attach() calls as well,
> with the correct gcontext passed in.
> 
> This series tries to clean the rest of things up.
> 
> I picked up patch 1 from monitor-oob series into this series (which is
> a missing of chardev frontend call fix for g_source_attach()), so that
> this series can be a complete fix.
> 
> Please review.  Thanks,
> 
> Peter Xu (3):
>   chardev: use backend chr context when watch for fe
>   chardev: let g_idle_add() be with chardev gcontext
>   chardev: introduce qemu_chr_timeout_add_ms()
> 
>  chardev/char-fe.c      |  2 +-
>  chardev/char-pty.c     | 16 ++++++++--------
>  chardev/char-socket.c  |  6 ++++--
>  chardev/char.c         | 21 +++++++++++++++++++++
>  hw/char/terminal3270.c |  7 ++++---
>  include/chardev/char.h |  3 +++
>  6 files changed, 41 insertions(+), 14 deletions(-)
> 
> -- 
> 2.14.3
> 

-- 
Peter Xu