monitor: do not use mb_read/mb_set for suspend_cnt
Clean up monitor_event to just use monitor_suspend/monitor_resume,
using mon->mux_out to protect against incorrect nesting (especially
on startup).
The only remaining case of reading suspend_cnt is in the can_read
callback, which is just advisory and can use qatomic_read.
As an extra benefit, mux_out is now simply protected by mon_lock.
Also, moving the prompt to the beginning of the main loop removes
it from the output in some error cases where QEMU does not actually
start successfully. It is not a full fix and it would be nice to
also remove the monitor heading, but this is already a small (though
unintentional) improvement.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/monitor/hmp.c b/monitor/hmp.c
index 5cab56d..69c1b7e 100644
--- a/monitor/hmp.c
+++ b/monitor/hmp.c
@@ -1401,45 +1401,42 @@
static void monitor_event(void *opaque, QEMUChrEvent event)
{
Monitor *mon = opaque;
- MonitorHMP *hmp_mon = container_of(mon, MonitorHMP, common);
switch (event) {
case CHR_EVENT_MUX_IN:
qemu_mutex_lock(&mon->mon_lock);
- mon->mux_out = 0;
- qemu_mutex_unlock(&mon->mon_lock);
- if (mon->reset_seen) {
- readline_restart(hmp_mon->rs);
+ if (mon->mux_out) {
+ mon->mux_out = 0;
monitor_resume(mon);
- monitor_flush(mon);
- } else {
- qatomic_mb_set(&mon->suspend_cnt, 0);
}
+ qemu_mutex_unlock(&mon->mon_lock);
break;
case CHR_EVENT_MUX_OUT:
- if (mon->reset_seen) {
- if (qatomic_mb_read(&mon->suspend_cnt) == 0) {
- monitor_printf(mon, "\n");
- }
- monitor_flush(mon);
- monitor_suspend(mon);
- } else {
- qatomic_inc(&mon->suspend_cnt);
- }
qemu_mutex_lock(&mon->mon_lock);
- mon->mux_out = 1;
+ if (!mon->mux_out) {
+ if (mon->reset_seen && !mon->suspend_cnt) {
+ monitor_puts_locked(mon, "\n");
+ } else {
+ monitor_flush_locked(mon);
+ }
+ monitor_suspend(mon);
+ mon->mux_out = 1;
+ }
qemu_mutex_unlock(&mon->mon_lock);
break;
case CHR_EVENT_OPENED:
monitor_printf(mon, "QEMU %s monitor - type 'help' for more "
"information\n", QEMU_VERSION);
- if (!mon->mux_out) {
- readline_restart(hmp_mon->rs);
- readline_show_prompt(hmp_mon->rs);
- }
+ qemu_mutex_lock(&mon->mon_lock);
mon->reset_seen = 1;
+ if (!mon->mux_out) {
+ /* Suspend-resume forces the prompt to be printed. */
+ monitor_suspend(mon);
+ monitor_resume(mon);
+ }
+ qemu_mutex_unlock(&mon->mon_lock);
mon_refcount++;
break;
