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Re: [Qemu-devel] [RFC v5 18/26] monitor: send event when request queue f
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [RFC v5 18/26] monitor: send event when request queue full |
Date: |
Thu, 14 Dec 2017 11:41:36 +0000 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Tue, Dec 05, 2017 at 01:51:52PM +0800, Peter Xu wrote:
> Set maximum QMP request queue length to 8. If queue full, instead of
> queue the command, we directly return a "request-dropped" event, telling
> client that specific command is dropped.
>
> Note that this flow control mechanism is only valid if OOB is enabled.
> If it's not, the effective queue length will always be 1, which strictly
> follows original behavior of QMP command handling (which never drop
> messages).
>
> Signed-off-by: Peter Xu <address@hidden>
> ---
> monitor.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/monitor.c b/monitor.c
> index c20e659740..f7923c4590 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -4029,6 +4029,8 @@ static void monitor_qmp_bh_dispatcher(void *data)
> }
> }
>
> +#define QMP_REQ_QUEUE_LEN_MAX (8)
> +
> static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens,
> void *opaque)
> {
> @@ -4061,6 +4063,19 @@ static void handle_qmp_command(JSONMessageParser
> *parser, GQueue *tokens,
> req_obj->id = id;
> req_obj->req = req;
>
> + if (qmp_oob_enabled(mon)) {
> + /* Drop the request if queue is full. */
> + if (mon->qmp.qmp_requests->length >= QMP_REQ_QUEUE_LEN_MAX) {
qmp_queue_lock must be held. Perhaps it's simplest to move this check
into the qmp_queue_lock critical section below and unlock before calling
qapi_event_send_request_dropped()...
> + qapi_event_send_request_dropped(id,
> + REQUEST_DROP_REASON_QUEUE_FULL,
> + NULL);
> + qobject_decref(id);
> + qobject_decref(req);
> + g_free(req_obj);
> + return;
> + }
> + }
> +
> /*
> * Put the request to the end of queue so that requests will be
> * handled in time order. Ownership for req_obj, req, id,
... down here.
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- Re: [Qemu-devel] [RFC v5 16/26] monitor: separate QMP parser and dispatcher, (continued)
[Qemu-devel] [RFC v5 17/26] qmp: add new event "request-dropped", Peter Xu, 2017/12/05
[Qemu-devel] [RFC v5 18/26] monitor: send event when request queue full, Peter Xu, 2017/12/05
- Re: [Qemu-devel] [RFC v5 18/26] monitor: send event when request queue full,
Stefan Hajnoczi <=
[Qemu-devel] [RFC v5 19/26] qapi: introduce new cmd option "allow-oob", Peter Xu, 2017/12/05
[Qemu-devel] [RFC v5 20/26] qmp: support out-of-band (oob) execution, Peter Xu, 2017/12/05