Re: [Qemu-devel] [RfC PATCH 2/2] console: add screendump-device qmp cmd

[Gerd Hoffmann <kraxel@redhat.com>]

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On 06/17/13 16:50, Luiz Capitulino wrote:
>>> > > +struct screendump_job {
>>> > > +    QEMUBH *bh;
>>> > > +    QemuConsole *con;
>>> > > +    char *filename;
>>> > > +};
>> > 
>> > We have a job API in the block layer.  Would it make sense to have a
>> > QMP-level job interface?
> I'd agree with this.

Something like the attached patch?  Which is just the bare minimum I'll
need for screendump.  Basically a one-off bottom half with some monitor
infrastructure (job id, error handling).  So it isn't for big jobs, but
for small jobs which have to wait for something before they execute
(spice-server, guest action, whatever).

If you wanna some more context: screendump on top of that is here:
https://www.kraxel.org/cgit/qemu/log/?h=rebase/pixman

[ not tested yet ]

cheers,
  Gerd

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>From bf1f7ec8a2baacc497e188ac38b24e5b0387b143 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue, 18 Jun 2013 09:21:03 +0200
Subject: [PATCH 1/3] [draft] monitor job

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 include/monitor/monitor.h |   10 +++++++
 monitor.c                 |   66 +++++++++++++++++++++++++++++++++++++++++++++
 qapi-schema.json          |   10 +++++++
 3 files changed, 86 insertions(+)

diff --git a/include/monitor/monitor.h b/include/monitor/monitor.h
index 1a6cfcf..6f5ec7e 100644
--- a/include/monitor/monitor.h
+++ b/include/monitor/monitor.h
@@ -47,6 +47,7 @@ typedef enum MonitorEvent {
     QEVENT_BALLOON_CHANGE,
     QEVENT_SPICE_MIGRATE_COMPLETED,
     QEVENT_GUEST_PANICKED,
+    QEVENT_JOB_COMPLETED,
 
     /* Add to 'monitor_event_names' array in monitor.c when
      * defining new events here */
@@ -100,4 +101,13 @@ int monitor_fdset_dup_fd_add(int64_t fdset_id, int dup_fd);
 int monitor_fdset_dup_fd_remove(int dup_fd);
 int monitor_fdset_dup_fd_find(int dup_fd);
 
+typedef struct monitor_job monitor_job;
+typedef void (*monitor_job_func)(void *opaque, Error **errp);
+
+uint64_t monitor_job_new_id(void);
+monitor_job *monitor_job_alloc(uint64_t id, monitor_job_func func,
+                               void *opaque);
+void monitor_job_queue(monitor_job *job);
+void monitor_job_cancel(monitor_job *job);
+
 #endif /* !MONITOR_H */
diff --git a/monitor.c b/monitor.c
index 70ae8f5..9a25c1e 100644
--- a/monitor.c
+++ b/monitor.c
@@ -496,6 +496,7 @@ static const char *monitor_event_names[] = {
     [QEVENT_BALLOON_CHANGE] = "BALLOON_CHANGE",
     [QEVENT_SPICE_MIGRATE_COMPLETED] = "SPICE_MIGRATE_COMPLETED",
     [QEVENT_GUEST_PANICKED] = "GUEST_PANICKED",
+    [QEVENT_JOB_COMPLETED] = "JOB_COMPLETED",
 };
 QEMU_BUILD_BUG_ON(ARRAY_SIZE(monitor_event_names) != QEVENT_MAX)
 
@@ -4863,3 +4864,68 @@ QemuOptsList qemu_mon_opts = {
         { /* end of list */ }
     },
 };
+
+struct monitor_job {
+    uint64_t id;
+    monitor_job_func func;
+    void *opaque;
+    QEMUBH *bh;
+};
+
+static void monitor_job_event(monitor_job *job, const char *result, Error *err)
+{
+    QObject *data;
+
+    data = qobject_from_jsonf("{ 'job-id': %" PRId64 ", 'result': %s }",
+                              job->id, result);
+    if (error_is_set(&err)) {
+        /* TODO: add error details */
+    }
+    monitor_protocol_event(QEVENT_JOB_COMPLETED, data);
+    qobject_decref(data);
+}
+
+static void monitor_job_bh(void *opaque)
+{
+    monitor_job *job = opaque;
+    Error *local_err = NULL;
+    const char *result;
+
+    job->func(job->opaque, &local_err);
+    result = error_is_set(&local_err) ? "success" : "failure";
+    monitor_job_event(job, result, local_err);
+    qemu_bh_delete(job->bh);
+    g_free(job);
+}
+
+uint64_t monitor_job_new_id(void)
+{
+    static uint64_t nextid = 1;
+    return nextid++;
+}
+
+monitor_job *monitor_job_alloc(uint64_t id, monitor_job_func func,
+                               void *opaque)
+{
+    monitor_job *job = g_new0(monitor_job, 1);
+
+    job->id = id;
+    job->func = func;
+    job->opaque = opaque;
+    return job;
+}
+
+void monitor_job_queue(monitor_job *job)
+{
+    job->bh = qemu_bh_new(monitor_job_bh, job);
+    qemu_bh_schedule(job->bh);
+}
+
+void monitor_job_cancel(monitor_job *job)
+{
+    monitor_job_event(job, "canceled", NULL);
+    if (job->bh) {
+        qemu_bh_delete(job->bh);
+    }
+    g_free(job);
+}
diff --git a/qapi-schema.json b/qapi-schema.json
index aced724..a449a43 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2515,6 +2515,16 @@
     'str': 'str' } }
 
 ##
+# @MonitorJob
+#
+# Monitor job id.
+#
+# Since 1.6
+##
+{ 'type': 'MonitorJob',
+  'data': { 'job-id': 'int' } }
+
+##
 # @NetdevUserOptions
 #
 # Use the user mode network stack which requires no administrator privilege to
-- 
1.7.9.7