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authorPaolo Bonzini <pbonzini@redhat.com>2023-03-03 13:32:13 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2023-05-25 10:18:33 +0200
commit6ee7c82d0df9bb6e972a8ea689b935df3ba37486 (patch)
treef99a5786fb54b9072069e498313d4336bd9aaa6a /monitor
parent4cb96b974265f97a9902b4458e50d01082572a16 (diff)
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>
Diffstat (limited to 'monitor')
-rw-r--r--monitor/hmp.c35
-rw-r--r--monitor/monitor-internal.h3
-rw-r--r--monitor/monitor.c9
3 files changed, 24 insertions, 23 deletions
diff --git a/monitor/hmp.c b/monitor/hmp.c
index 5cab56d355..69c1b7e98a 100644
--- a/monitor/hmp.c
+++ b/monitor/hmp.c
@@ -1401,45 +1401,42 @@ static void monitor_read(void *opaque, const uint8_t *buf, int size)
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");
+ qemu_mutex_lock(&mon->mon_lock);
+ if (!mon->mux_out) {
+ if (mon->reset_seen && !mon->suspend_cnt) {
+ monitor_puts_locked(mon, "\n");
+ } else {
+ monitor_flush_locked(mon);
}
- monitor_flush(mon);
monitor_suspend(mon);
- } else {
- qatomic_inc(&mon->suspend_cnt);
+ mon->mux_out = 1;
}
- qemu_mutex_lock(&mon->mon_lock);
- 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);
+ qemu_mutex_lock(&mon->mon_lock);
+ mon->reset_seen = 1;
if (!mon->mux_out) {
- readline_restart(hmp_mon->rs);
- readline_show_prompt(hmp_mon->rs);
+ /* Suspend-resume forces the prompt to be printed. */
+ monitor_suspend(mon);
+ monitor_resume(mon);
}
- mon->reset_seen = 1;
+ qemu_mutex_unlock(&mon->mon_lock);
mon_refcount++;
break;
diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h
index 53e3808054..61c9b6916d 100644
--- a/monitor/monitor-internal.h
+++ b/monitor/monitor-internal.h
@@ -94,7 +94,6 @@ typedef struct HMPCommand {
struct Monitor {
CharBackend chr;
- int reset_seen;
int suspend_cnt; /* Needs to be accessed atomically */
bool is_qmp;
bool skip_flush;
@@ -115,8 +114,8 @@ struct Monitor {
QLIST_HEAD(, mon_fd_t) fds;
GString *outbuf;
guint out_watch;
- /* Read under either BQL or mon_lock, written with BQL+mon_lock. */
int mux_out;
+ int reset_seen;
};
struct MonitorHMP {
diff --git a/monitor/monitor.c b/monitor/monitor.c
index 20e33e28d2..15f97538ef 100644
--- a/monitor/monitor.c
+++ b/monitor/monitor.c
@@ -569,10 +569,15 @@ static void monitor_accept_input(void *opaque)
{
Monitor *mon = opaque;
- if (!monitor_is_qmp(mon)) {
+ qemu_mutex_lock(&mon->mon_lock);
+ if (!monitor_is_qmp(mon) && mon->reset_seen) {
MonitorHMP *hmp_mon = container_of(mon, MonitorHMP, common);
assert(hmp_mon->rs);
+ readline_restart(hmp_mon->rs);
+ qemu_mutex_unlock(&mon->mon_lock);
readline_show_prompt(hmp_mon->rs);
+ } else {
+ qemu_mutex_unlock(&mon->mon_lock);
}
qemu_chr_fe_accept_input(&mon->chr);
@@ -603,7 +608,7 @@ int monitor_can_read(void *opaque)
{
Monitor *mon = opaque;
- return !qatomic_mb_read(&mon->suspend_cnt);
+ return !qatomic_read(&mon->suspend_cnt);
}
void monitor_list_append(Monitor *mon)