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.kis...@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;