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GET /api/patches/2196389/?format=api
{ "id": 2196389, "url": "http://patchwork.ozlabs.org/api/patches/2196389/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260213171622.55629-2-zhangckid@gmail.com/", "project": { "id": 14, "url": "http://patchwork.ozlabs.org/api/projects/14/?format=api", "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": "", "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260213171622.55629-2-zhangckid@gmail.com>", "list_archive_url": null, "date": "2026-02-13T17:16:20", "name": "[V4,2/4] iothread: introduce iothread_ref/unref to track attached devices", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "40ae6e05453c61fe00172e21208bfc415f842f39", "submitter": { "id": 72278, "url": "http://patchwork.ozlabs.org/api/people/72278/?format=api", "name": "Zhang Chen", "email": "zhangckid@gmail.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260213171622.55629-2-zhangckid@gmail.com/mbox/", "series": [ { "id": 492123, "url": "http://patchwork.ozlabs.org/api/series/492123/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/list/?series=492123", "date": "2026-02-13T17:16:20", "name": "[V4,1/4] qapi/misc: Fix missed query-iothreads items", "version": 4, "mbox": "http://patchwork.ozlabs.org/series/492123/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2196389/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2196389/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org>", "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=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20230601 header.b=SPEpB4GJ;\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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David Alan Gilbert\" <dave@treblig.org>,\n Eric Blake <eblake@redhat.com>, Markus Armbruster <armbru@redhat.com>,\n \"Michael S . Tsirkin\" <mst@redhat.com>,\n Stefan Hajnoczi <stefanha@redhat.com>", "Cc": "Zhang Chen <zhangckid@gmail.com>", "Subject": "[PATCH V4 2/4] iothread: introduce iothread_ref/unref to track\n attached devices", "Date": "Sat, 14 Feb 2026 01:16:20 +0800", "Message-ID": "<20260213171622.55629-2-zhangckid@gmail.com>", "X-Mailer": "git-send-email 2.49.0", "In-Reply-To": "<20260213171622.55629-1-zhangckid@gmail.com>", "References": "<20260213171622.55629-1-zhangckid@gmail.com>", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "Received-SPF": "pass client-ip=2607:f8b0:4864:20::52a;\n envelope-from=zhangckid@gmail.com; helo=mail-pg1-x52a.google.com", "X-Spam_score_int": "-20", "X-Spam_score": "-2.1", "X-Spam_bar": "--", "X-Spam_report": "(-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1,\n DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001,\n RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001,\n 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 <qemu-devel.nongnu.org>", "List-Unsubscribe": "<https://lists.nongnu.org/mailman/options/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>", "List-Archive": "<https://lists.nongnu.org/archive/html/qemu-devel>", "List-Post": "<mailto:qemu-devel@nongnu.org>", "List-Help": "<mailto:qemu-devel-request@nongnu.org?subject=help>", "List-Subscribe": "<https://lists.nongnu.org/mailman/listinfo/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=subscribe>", "Errors-To": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org", "Sender": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org" }, "content": "Currently, IOThreads do not maintain a record of which devices are\nassociated with them. This makes it difficult to monitor the\nworkload distribution of IOThreads, especially in complex\nhotplug scenarios involving multiple virtio-blk or virtio-scsi devices.\n\nThis patch introduces a reference counting and tracking mechanism\nwithin the IOThread object:\n\n- iothread_ref(): Increments the attachment counter and prepends the\n device's QOM path to a list. Note: The IOThread takes ownership of\n the passed 'holder' string.\n- iothread_unref(): Searches for the device path using a custom\n string comparison (g_strcmp0), decrements the counter, and\n releases the associated memory upon a successful match.\n- attached_cnt: Tracks the number of active device attachments.\n- attached_dev: A GList storing the QOM paths of attached devices\n for runtime introspection.\n\nThis infrastructure allows management tools and QMP commands to\nquery the attachment status of IOThreads.\n\nSigned-off-by: Zhang Chen <zhangckid@gmail.com>\n---\n include/system/iothread.h | 4 ++++\n iothread.c | 35 +++++++++++++++++++++++++++++++++++\n 2 files changed, 39 insertions(+)", "diff": "diff --git a/include/system/iothread.h b/include/system/iothread.h\nindex e26d13c6c7..4a2ffdb9bd 100644\n--- a/include/system/iothread.h\n+++ b/include/system/iothread.h\n@@ -33,6 +33,8 @@ struct IOThread {\n bool stopping; /* has iothread_stop() been called? */\n bool running; /* should iothread_run() continue? */\n int thread_id;\n+ int attached_cnt;\n+ GList *attached_dev;\n \n /* AioContext poll parameters */\n int64_t poll_max_ns;\n@@ -48,6 +50,8 @@ char *iothread_get_id(IOThread *iothread);\n IOThread *iothread_by_id(const char *id);\n AioContext *iothread_get_aio_context(IOThread *iothread);\n GMainContext *iothread_get_g_main_context(IOThread *iothread);\n+void iothread_ref(IOThread *iothread, const char* holder);\n+void iothread_unref(IOThread *iothread, const char* holder);\n \n /*\n * Helpers used to allocate iothreads for internal use. These\ndiff --git a/iothread.c b/iothread.c\nindex caf68e0764..b869637497 100644\n--- a/iothread.c\n+++ b/iothread.c\n@@ -36,6 +36,41 @@\n #define IOTHREAD_POLL_MAX_NS_DEFAULT 0ULL\n #endif\n \n+/*\n+ * Increment iothread's reference count,\n+ * and add holder device path to the list.\n+ */\n+void iothread_ref(IOThread *iothread, const char *holder)\n+{\n+ iothread->attached_cnt++;\n+ iothread->attached_dev = g_list_prepend(iothread->attached_dev,\n+ (gpointer)holder);\n+}\n+\n+/*\n+ * Decrement iothread's reference count,\n+ * and delete holder device path from the list.\n+ */\n+void iothread_unref(IOThread *iothread, const char *holder)\n+{\n+ if (iothread->attached_cnt > 0) {\n+ GList *link = g_list_find_custom(iothread->attached_dev,\n+ holder, (GCompareFunc)g_strcmp0);\n+\n+ if (link) {\n+ g_free(link->data);\n+ iothread->attached_dev = g_list_delete_link(iothread->attached_dev,\n+ link);\n+ iothread->attached_cnt--;\n+ } else {\n+ error_report(\"iohtread_unref can't find device. attached_dev=%s\",\n+ holder);\n+ }\n+ } else {\n+ error_report(\"iohtread_unref counter error. attached_dev=%s\", holder);\n+ }\n+}\n+\n static void *iothread_run(void *opaque)\n {\n IOThread *iothread = opaque;\n", "prefixes": [ "V4", "2/4" ] }