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chardev: Use timer instead of bottom-half to postpone open event

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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>
This commit is contained in:
Jan Kiszka 2012-10-12 09:52:49 +02:00 committed by Aurelien Jarno
parent 40e3acc18f
commit ac4119c023
3 changed files with 13 additions and 12 deletions
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13
qemu-char.c
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@ -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);
}
}

2
qemu-char.h
View File

@ -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;

10
vl.c
View File

@ -3551,6 +3551,11 @@ 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)
@ -3618,11 +3623,6 @@ 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();