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qmp: Resume OOB-enabled monitor before processing the request

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monitor_qmp_dispatcher_co() needs to resume the monitor if
handle_qmp_command() suspended it.  Two cases:

1. OOB enabled: suspended if mon->qmp_requests has no more space

2. OOB disabled: suspended always

We resume only after we processed the request.  Which can take a long
time.

Resume the monitor right when the queue has space to keep the monitor
available for out-of-band commands even in this corner case.

Leave the "OOB disabled" case alone.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20210201161504.1976989-4-armbru@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
[Trailing whitespace tidied up]
This commit is contained in:
Markus Armbruster 2021-02-01 17:15:04 +01:00
parent f680405f45
commit 88daf0996c
1 changed files with 27 additions and 6 deletions
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33
monitor/qmp.c
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@ -214,7 +214,7 @@ void coroutine_fn monitor_qmp_dispatcher_co(void *data)
{
QMPRequest *req_obj = NULL;
QDict *rsp;
bool need_resume;
bool oob_enabled;
MonitorQMP *mon;
while (true) {
@ -273,11 +273,32 @@ void coroutine_fn monitor_qmp_dispatcher_co(void *data)
aio_co_schedule(qemu_get_aio_context(), qmp_dispatcher_co);
qemu_coroutine_yield();
/*
* @req_obj has a request, we hold req_obj->mon->qmp_queue_lock
*/
mon = req_obj->mon;
/* qmp_oob_enabled() might change after "qmp_capabilities" */
need_resume = !qmp_oob_enabled(mon) ||
mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1;
/*
* We need to resume the monitor if handle_qmp_command()
* suspended it. Two cases:
* 1. OOB enabled: mon->qmp_requests has no more space
* Resume right away, so that OOB commands can get executed while
* this request is being processed.
* 2. OOB disabled: always
* Resume only after we're done processing the request,
* We need to save qmp_oob_enabled() for later, because
* qmp_qmp_capabilities() can change it.
*/
oob_enabled = qmp_oob_enabled(mon);
if (oob_enabled
&& mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1) {
monitor_resume(&mon->common);
}
qemu_mutex_unlock(&mon->qmp_queue_lock);
/* Process request */
if (req_obj->req) {
if (trace_event_get_state(TRACE_MONITOR_QMP_CMD_IN_BAND)) {
QDict *qdict = qobject_to(QDict, req_obj->req);
@ -298,10 +319,10 @@ void coroutine_fn monitor_qmp_dispatcher_co(void *data)
qobject_unref(rsp);
}
if (need_resume) {
/* Pairs with the monitor_suspend() in handle_qmp_command() */
if (!oob_enabled) {
monitor_resume(&mon->common);
}
qmp_request_free(req_obj);
/*