{"id":2221294,"url":"http://patchwork.ozlabs.org/api/1.0/patches/2221294/?format=json","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/1.0/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260409-work-qmp-monitor-hotplug-v4-1-89c4fdf69df1@kernel.org>","date":"2026-04-09T07:18:18","name":"[v4,1/5] monitor: store monitor id in Monitor struct","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"bb8ba1bde215b0f51c9b78399e65cf715fe7f031","submitter":{"id":82326,"url":"http://patchwork.ozlabs.org/api/1.0/people/82326/?format=json","name":"Christian Brauner","email":"brauner@kernel.org"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20260409-work-qmp-monitor-hotplug-v4-1-89c4fdf69df1@kernel.org/mbox/","series":[{"id":499242,"url":"http://patchwork.ozlabs.org/api/1.0/series/499242/?format=json","date":"2026-04-09T07:18:17","name":"monitor: add dynamic QMP monitor hotplug support","version":4,"mbox":"http://patchwork.ozlabs.org/series/499242/mbox/"}],"check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2221294/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=W95FoXUC;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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charset=\"utf-8\"","Content-Transfer-Encoding":"7bit","Message-Id":"<20260409-work-qmp-monitor-hotplug-v4-1-89c4fdf69df1@kernel.org>","References":"<20260409-work-qmp-monitor-hotplug-v4-0-89c4fdf69df1@kernel.org>","In-Reply-To":"<20260409-work-qmp-monitor-hotplug-v4-0-89c4fdf69df1@kernel.org>","To":"qemu-devel@nongnu.org","Cc":"Markus Armbruster , Eric Blake ,\n Fabiano Rosas , Laurent Vivier ,\n Paolo Bonzini , Thomas Huth ,\n\t=?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , =?utf-8?q?Dani?=\n\t=?utf-8?q?el_P=2E_Berrang=C3=A9?= ,\n Christian Brauner ","X-Mailer":"b4 0.16-dev","X-Developer-Signature":"v=1; a=openpgp-sha256; l=7163; i=brauner@kernel.org;\n h=from:subject:message-id; bh=UUlm8e38M0cU+sF8CtorJzdeLsTyxHdaQbX9fCniErs=;\n b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWReDzpq7DWn5f3W3yXX3G5ecmOcuMjP8N9CZR/pxVVn+\n mUnplov6ShlYRDjYpAVU2RxaDcJl1vOU7HZKFMDZg4rE8gQBi5OAZjIVl2G/zWLE10+bF56armg\n e7mVpOLPPVd5FKNOLa52UZ77p1qf3ZPhv5PMRZEk+UsK64SYxM3FNslG8lZvjOKSf9znsW/xs8M\n eHAA=","X-Developer-Key":"i=brauner@kernel.org; a=openpgp;\n fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624","Received-SPF":"pass client-ip=172.234.252.31; envelope-from=brauner@kernel.org;\n helo=sea.source.kernel.org","X-Spam_score_int":"-25","X-Spam_score":"-2.6","X-Spam_bar":"--","X-Spam_report":"(-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.54,\n DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001,\n SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no","X-Spam_action":"no action","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"qemu development ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"},"content":"Add an 'id' field to struct Monitor. The id field stores the monitor\nidentifier from MonitorOptions which was previously parsed but\ndiscarded.\n\nAuto-generate a unique id (\"mon0\", \"mon1\", ...) for QMP monitors\ncreated via CLI without an explicit id, so that every QMP monitor is\naddressable by monitor-remove and always appears with an id in\nquery-monitors output.\n\nExtend monitor_init_qmp() to accept an id parameter so it is set\nbefore the monitor is added to mon_list.\n\nFor iothread monitors, move monitor_list_append() from the setup BH to\nthe caller so monitor_find_by_id() can detect duplicates immediately.\nWithout this, two concurrent monitor-add calls could both pass the\nduplicate check before either BH runs. This means the monitor is now\nvisible in mon_list before its chardev handlers are set up, which was\nnot the case before. This is safe because the request queue is still\nempty (no chardev handlers means no monitor_qmp_read(), so the\ndispatcher finds nothing to dispatch) and event broadcast is handled\nbelow.\n\nThis requires initializing mon->commands = &qmp_cap_negotiation_commands\nbefore monitor_list_append(). Without it, commands is NULL (from\ng_new0) and monitor_qapi_event_emit() would not skip the monitor during\nevent broadcast -- its check is specifically for the\nqmp_cap_negotiation_commands pointer, so a NULL falls through to\nqmp_send_response() on an uninitialized monitor. CHR_EVENT_OPENED sets\ncommands to the same value again later.\n\nAdd monitor_find_by_id() to look up monitors by identifier. The lookup\ntakes monitor_lock to serialize with the I/O thread BH that modifies\nmon_list, but releases it before returning. The caller must hold the\nBQL to ensure the returned pointer remains valid since only BQL holders\ncan destroy monitors.\n\nFree the id string in monitor_data_destroy().\n\nSigned-off-by: Christian Brauner (Amutable) \n---\n include/monitor/monitor.h | 3 ++-\n monitor/monitor-internal.h | 4 +++-\n monitor/monitor.c | 21 ++++++++++++++++++++-\n monitor/qmp.c | 15 ++++++++++++---\n 4 files changed, 37 insertions(+), 6 deletions(-)","diff":"diff --git a/include/monitor/monitor.h b/include/monitor/monitor.h\nindex 296690e1f1..a4e6aaa97f 100644\n--- a/include/monitor/monitor.h\n+++ b/include/monitor/monitor.h\n@@ -19,7 +19,8 @@ bool monitor_cur_is_qmp(void);\n \n void monitor_init_globals(void);\n void monitor_init_globals_core(void);\n-void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp);\n+void monitor_init_qmp(Chardev *chr, bool pretty, const char *id,\n+ Error **errp);\n void monitor_init_hmp(Chardev *chr, bool use_readline, Error **errp);\n int monitor_init(MonitorOptions *opts, bool allow_hmp, Error **errp);\n int monitor_init_opts(QemuOpts *opts, Error **errp);\ndiff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h\nindex feca111ae3..24d3b1900e 100644\n--- a/monitor/monitor-internal.h\n+++ b/monitor/monitor-internal.h\n@@ -98,7 +98,7 @@ struct Monitor {\n bool is_qmp;\n bool skip_flush;\n bool use_io_thread;\n-\n+ char *id;\n char *mon_cpu_path;\n QTAILQ_ENTRY(Monitor) entry;\n \n@@ -181,6 +181,8 @@ void monitor_data_destroy_qmp(MonitorQMP *mon);\n void coroutine_fn monitor_qmp_dispatcher_co(void *data);\n void qmp_dispatcher_co_wake(void);\n \n+Monitor *monitor_find_by_id(const char *id);\n+\n int get_monitor_def(Monitor *mon, int64_t *pval, const char *name);\n void handle_hmp_command(MonitorHMP *mon, const char *cmdline);\n int hmp_compare_cmd(const char *name, const char *list);\ndiff --git a/monitor/monitor.c b/monitor/monitor.c\nindex 00b93ed612..10a32150e9 100644\n--- a/monitor/monitor.c\n+++ b/monitor/monitor.c\n@@ -622,6 +622,7 @@ void monitor_data_init(Monitor *mon, bool is_qmp, bool skip_flush,\n \n void monitor_data_destroy(Monitor *mon)\n {\n+ g_free(mon->id);\n g_free(mon->mon_cpu_path);\n qemu_chr_fe_deinit(&mon->chr, false);\n if (monitor_is_qmp(mon)) {\n@@ -633,6 +634,24 @@ void monitor_data_destroy(Monitor *mon)\n qemu_mutex_destroy(&mon->mon_lock);\n }\n \n+/*\n+ * Look up a monitor by its id. The monitor_lock is released before\n+ * returning, so the caller must hold the BQL to ensure the returned\n+ * pointer remains valid (only BQL holders can destroy monitors).\n+ */\n+Monitor *monitor_find_by_id(const char *id)\n+{\n+ Monitor *mon;\n+\n+ QEMU_LOCK_GUARD(&monitor_lock);\n+ QTAILQ_FOREACH(mon, &mon_list, entry) {\n+ if (mon->id && strcmp(mon->id, id) == 0) {\n+ return mon;\n+ }\n+ }\n+ return NULL;\n+}\n+\n void monitor_cleanup(void)\n {\n /*\n@@ -732,7 +751,7 @@ int monitor_init(MonitorOptions *opts, bool allow_hmp, Error **errp)\n \n switch (opts->mode) {\n case MONITOR_MODE_CONTROL:\n- monitor_init_qmp(chr, opts->pretty, errp);\n+ monitor_init_qmp(chr, opts->pretty, opts->id, errp);\n break;\n case MONITOR_MODE_READLINE:\n if (!allow_hmp) {\ndiff --git a/monitor/qmp.c b/monitor/qmp.c\nindex 687019811f..bba69a3a40 100644\n--- a/monitor/qmp.c\n+++ b/monitor/qmp.c\n@@ -510,10 +510,10 @@ static void monitor_qmp_setup_handlers_bh(void *opaque)\n qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,\n monitor_qmp_read, monitor_qmp_event,\n NULL, &mon->common, context, true);\n- monitor_list_append(&mon->common);\n }\n \n-void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp)\n+void monitor_init_qmp(Chardev *chr, bool pretty, const char *id,\n+ Error **errp)\n {\n MonitorQMP *mon = g_new0(MonitorQMP, 1);\n \n@@ -527,12 +527,20 @@ void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp)\n monitor_data_init(&mon->common, true, false,\n qemu_chr_has_feature(chr, QEMU_CHAR_FEATURE_GCONTEXT));\n \n+ if (id) {\n+ mon->common.id = g_strdup(id);\n+ } else {\n+ static unsigned int qmp_monitor_id_counter;\n+ mon->common.id = g_strdup_printf(\"mon%u\", qmp_monitor_id_counter++);\n+ }\n mon->pretty = pretty;\n \n qemu_mutex_init(&mon->qmp_queue_lock);\n mon->qmp_requests = g_queue_new();\n \n json_message_parser_init(&mon->parser, handle_qmp_command, mon, NULL);\n+ /* Prevent event broadcast to an uninitialized monitor. */\n+ mon->commands = &qmp_cap_negotiation_commands;\n if (mon->common.use_io_thread) {\n /*\n * Make sure the old iowatch is gone. It's possible when\n@@ -551,7 +559,8 @@ void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp)\n */\n aio_bh_schedule_oneshot(iothread_get_aio_context(mon_iothread),\n monitor_qmp_setup_handlers_bh, mon);\n- /* The bottom half will add @mon to @mon_list */\n+ /* Synchronous insert for immediate duplicate detection. */\n+ monitor_list_append(&mon->common);\n } else {\n qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,\n monitor_qmp_read, monitor_qmp_event,\n","prefixes":["v4","1/5"]}