{"id":2219333,"url":"http://patchwork.ozlabs.org/api/1.0/patches/2219333/?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":"<20260402-work-qmp-monitor-hotplug-v1-2-6313a5cdd574@kernel.org>","date":"2026-04-02T21:19:17","name":"[2/5] monitor/qmp: add infrastructure for safe dynamic monitor removal","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"fc22dfd9e8a8304735c523e4a66444bc0fb069d5","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/20260402-work-qmp-monitor-hotplug-v1-2-6313a5cdd574@kernel.org/mbox/","series":[{"id":498554,"url":"http://patchwork.ozlabs.org/api/1.0/series/498554/?format=json","date":"2026-04-02T21:19:15","name":"monitor: add dynamic QMP monitor hotplug support","version":1,"mbox":"http://patchwork.ozlabs.org/series/498554/mbox/"}],"check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2219333/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=dgAYVc21;\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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Thu, 02 Apr 2026 17:19:44 -0400","from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58])\n by tor.source.kernel.org (Postfix) with ESMTP id A6ABB60123;\n Thu, 2 Apr 2026 21:19:35 +0000 (UTC)","by smtp.kernel.org (Postfix) with ESMTPSA id 3E04DC116C6;\n Thu, 2 Apr 2026 21:19:33 +0000 (UTC)"],"DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org;\n s=k20201202; t=1775164775;\n bh=bSL21DMJvdPmisuJ4sR+uubo6LsKzZepTDyv0CmheLU=;\n h=From:Date:Subject:References:In-Reply-To:To:Cc:From;\n b=dgAYVc21yM/2Vjc90j9dbQAcYoc1fLCXqQkzFCt296qDhe2Go0aqs8USaGnebPNio\n ynpNo/A7T9a7UCDM631goZ8SsOzdpIaMKYQX1ErQbSbfG/ExO8qx45NqA2m+gqluwU\n V/PbZAtnNluv/ZWQGVeO0CBrQkoABToqBhvY1qfgXhiOKpoiwilUcLqJZ/lYAzhVVE\n D2Ea7z9M+rDtOBrJngc8Vj9N9tsnoZDe2Vx8kRupZzQ8vrqhdvMJQS9AkglcGvYWuh\n crh7pCL48m58VQB7JXVlRn54cKyWrVaH6BXGYLxKQWNZ89CsAezoQ2d8Cblh5AtwkO\n guTavDLZHgn9A==","From":"Christian Brauner ","Date":"Thu, 02 Apr 2026 23:19:17 +0200","Subject":"[PATCH 2/5] monitor/qmp: add infrastructure for safe dynamic\n monitor removal","MIME-Version":"1.0","Content-Type":"text/plain; charset=\"utf-8\"","Content-Transfer-Encoding":"7bit","Message-Id":"<20260402-work-qmp-monitor-hotplug-v1-2-6313a5cdd574@kernel.org>","References":"<20260402-work-qmp-monitor-hotplug-v1-0-6313a5cdd574@kernel.org>","In-Reply-To":"<20260402-work-qmp-monitor-hotplug-v1-0-6313a5cdd574@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=4106; i=brauner@kernel.org;\n h=from:subject:message-id; bh=bSL21DMJvdPmisuJ4sR+uubo6LsKzZepTDyv0CmheLU=;\n b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWSeuxv/foer4afmkxfEPMt39E6PC9TgvHlBZ07SqQKXN\n a7dR9+ndJSyMIhxMciKKbI4tJuEyy3nqdhslKkBM4eVCWQIAxenAEyk/hYjw2G3CWZtnW2CX7LM\n vapdfY1U3x/pD4t3eBmSUHDn67XPtQz/LHwzfi7IfaqYtNZi1Yl3WkKnl0rcP+jTvmj+tmzNNYV\n ZXAA=","X-Developer-Key":"i=brauner@kernel.org; a=openpgp;\n fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624","Received-SPF":"pass client-ip=172.105.4.254; envelope-from=brauner@kernel.org;\n helo=tor.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=-0.542,\n DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001,\n RCVD_IN_VALIDITY_RPBL_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":"Extract monitor_qmp_destroy() from the shutdown-time monitor_cleanup()\npath to allow destroying a single QMP monitor at runtime without\nshutting down the entire dispatcher coroutine.\n\nExport monitor_qmp_cleanup_queue_and_resume() so that monitor-remove\ncan drain pending requests before destroying the monitor.\n\nAdd qmp_dispatcher_current_mon tracking in the dispatcher coroutine to\nhandle the case where a monitor sends monitor-remove targeting itself.\nAfter dispatching each request, the dispatcher checks the dead flag: if\nset, it calls monitor_qmp_destroy() and clears the tracking pointer.\n\nBoth the dispatcher yield points and QMP command handlers run under the\nBQL, so no additional locking is needed for qmp_dispatcher_current_mon.\n\nSigned-off-by: Christian Brauner (Amutable) \n---\n monitor/monitor-internal.h | 3 +++\n monitor/qmp.c | 36 +++++++++++++++++++++++++++++++++++-\n 2 files changed, 38 insertions(+), 1 deletion(-)","diff":"diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h\nindex 8f5fe7c111..40f76ef5a0 100644\n--- a/monitor/monitor-internal.h\n+++ b/monitor/monitor-internal.h\n@@ -181,10 +181,13 @@ void monitor_fdsets_cleanup(void);\n \n void qmp_send_response(MonitorQMP *mon, const QDict *rsp);\n void monitor_data_destroy_qmp(MonitorQMP *mon);\n+void monitor_qmp_destroy(MonitorQMP *mon);\n+void monitor_qmp_cleanup_queue_and_resume(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+bool monitor_qmp_dispatcher_is_servicing(MonitorQMP *mon);\n \n int get_monitor_def(Monitor *mon, int64_t *pval, const char *name);\n void handle_hmp_command(MonitorHMP *mon, const char *cmdline);\ndiff --git a/monitor/qmp.c b/monitor/qmp.c\nindex 5fbc7af074..0d393f3c96 100644\n--- a/monitor/qmp.c\n+++ b/monitor/qmp.c\n@@ -71,6 +71,13 @@ typedef struct QMPRequest QMPRequest;\n \n QmpCommandList qmp_commands, qmp_cap_negotiation_commands;\n \n+/*\n+ * The monitor currently being serviced by the dispatcher coroutine.\n+ * Both the dispatcher and QMP command handlers (monitor-remove) run\n+ * under the BQL, so no additional locking is needed.\n+ */\n+static MonitorQMP *qmp_dispatcher_current_mon;\n+\n static bool qmp_oob_enabled(MonitorQMP *mon)\n {\n return mon->capab[QMP_CAPABILITY_OOB];\n@@ -98,7 +105,7 @@ static void monitor_qmp_cleanup_req_queue_locked(MonitorQMP *mon)\n }\n }\n \n-static void monitor_qmp_cleanup_queue_and_resume(MonitorQMP *mon)\n+void monitor_qmp_cleanup_queue_and_resume(MonitorQMP *mon)\n {\n QEMU_LOCK_GUARD(&mon->qmp_queue_lock);\n \n@@ -287,6 +294,7 @@ void coroutine_fn monitor_qmp_dispatcher_co(void *data)\n */\n \n mon = req_obj->mon;\n+ qmp_dispatcher_current_mon = mon;\n \n /*\n * We need to resume the monitor if handle_qmp_command()\n@@ -347,6 +355,16 @@ void coroutine_fn monitor_qmp_dispatcher_co(void *data)\n }\n \n qmp_request_free(req_obj);\n+\n+ /*\n+ * If monitor-remove was called while we were dispatching a\n+ * request on this monitor, the monitor was marked dead and\n+ * removed from mon_list but destruction was deferred to us.\n+ */\n+ if (mon->common.dead) {\n+ monitor_qmp_destroy(mon);\n+ }\n+ qmp_dispatcher_current_mon = NULL;\n }\n qatomic_set(&qmp_dispatcher_co, NULL);\n }\n@@ -499,6 +517,22 @@ void monitor_data_destroy_qmp(MonitorQMP *mon)\n g_queue_free(mon->qmp_requests);\n }\n \n+/*\n+ * Destroy a single dynamically-added QMP monitor.\n+ * The monitor must already have been removed from mon_list.\n+ */\n+void monitor_qmp_destroy(MonitorQMP *mon)\n+{\n+ monitor_flush(&mon->common);\n+ monitor_data_destroy(&mon->common);\n+ g_free(mon);\n+}\n+\n+bool monitor_qmp_dispatcher_is_servicing(MonitorQMP *mon)\n+{\n+ return qmp_dispatcher_current_mon == mon;\n+}\n+\n static void monitor_qmp_setup_handlers_bh(void *opaque)\n {\n MonitorQMP *mon = opaque;\n","prefixes":["2/5"]}