Monitor code now can be run in more than one thread. Let it be thread
safe when accessing suspend_cnt counter.
Reviewed-by: Eric Blake
Signed-off-by: Peter Xu
---
monitor.c | 15 ---
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/monitor.c b/monitor.c
index 92114aaa80..60bcf67b3a 100644
--- a/monitor.c
+++ b/monitor.c
@@ -190,7 +190,7 @@ struct Monitor {
CharBackend chr;
int reset_seen;
int flags;
-int suspend_cnt;
+int suspend_cnt;/* Needs to be accessed atomically */
bool skip_flush;
bool use_io_thr;
@@ -3864,7 +3864,7 @@ static int monitor_can_read(void *opaque)
{
Monitor *mon = opaque;
-return (mon->suspend_cnt == 0) ? 1 : 0;
+return !atomic_mb_read(&mon->suspend_cnt);
}
/*
@@ -3996,7 +3996,7 @@ int monitor_suspend(Monitor *mon)
{
if (!mon->rs)
return -ENOTTY;
-mon->suspend_cnt++;
+atomic_inc(&mon->suspend_cnt);
return 0;
}
@@ -4004,8 +4004,9 @@ void monitor_resume(Monitor *mon)
{
if (!mon->rs)
return;
-if (--mon->suspend_cnt == 0)
+if (atomic_dec_fetch(&mon->suspend_cnt) == 0) {
readline_show_prompt(mon->rs);
+}
}
static QObject *get_qmp_greeting(Monitor *mon)
@@ -4070,19 +4071,19 @@ static void monitor_event(void *opaque, int event)
monitor_resume(mon);
monitor_flush(mon);
} else {
-mon->suspend_cnt = 0;
+atomic_mb_set(&mon->suspend_cnt, 0);
}
break;
case CHR_EVENT_MUX_OUT:
if (mon->reset_seen) {
-if (mon->suspend_cnt == 0) {
+if (atomic_mb_read(&mon->suspend_cnt) == 0) {
monitor_printf(mon, "\n");
}
monitor_flush(mon);
monitor_suspend(mon);
} else {
-mon->suspend_cnt++;
+atomic_inc(&mon->suspend_cnt);
}
qemu_mutex_lock(&mon->out_lock);
mon->mux_out = 1;
--
2.14.3