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Tsirkin'" , Stefan Hajnoczi , Paolo Bonzini , =?UTF-8?q?=27Daniel=20P=20=2E=20Berrang=C3=A9=27?= , Jason Wang Cc: Zhang Chen Subject: [PATCH V14 02/15] iothread: introduce holder tracking Date: Tue, 1 Sep 2026 00:00:23 +0800 Message-ID: <20260831160038.221776-3-zhangckid@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260831160038.221776-1-zhangckid@gmail.com> References: <20260831160038.221776-1-zhangckid@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::635; envelope-from=zhangckid@gmail.com; helo=mail-pl1-x635.google.com X-Spam_score_int: 26 X-Spam_score: 2.6 X-Spam_bar: ++ X-Spam_report: (2.6 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_BL_SPAMCOP_NET=1.347, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no 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: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org IOThreads do not record the QOM objects and block exports that use them, making runtime introspection and hotplug debugging difficult. Add: - holders: a list describing what is holding an iothread - iothread_ref(): add a holder to the list - iothread_unref(): remove a holder from the list A holder can identify either a QOM object or a block export. A later patch will expose this information through query-iothreads. Reviewed-by: Stefan Hajnoczi Reviewed-by: Markus Armbruster Signed-off-by: Zhang Chen --- include/system/iothread.h | 5 +++ iothread.c | 63 ++++++++++++++++++++++++++ qapi/misc.json | 94 ++++++++++++++++++++++++++++++++++----- 3 files changed, 150 insertions(+), 12 deletions(-) diff --git a/include/system/iothread.h b/include/system/iothread.h index a1ef7696cb..b8aeb32b0e 100644 --- a/include/system/iothread.h +++ b/include/system/iothread.h @@ -18,6 +18,7 @@ #include "qemu/thread.h" #include "qom/object.h" #include "system/event-loop-base.h" +#include "qapi/qapi-types-misc.h" #define TYPE_IOTHREAD "iothread" @@ -50,6 +51,7 @@ struct IOThread { bool stopping; /* has iothread_stop() been called? */ bool running; /* should iothread_run() continue? */ int thread_id; + IOThreadHolderList *holders; /* AioContext poll parameters */ int64_t poll_max_ns; @@ -82,4 +84,7 @@ void iothread_destroy(IOThread *iothread); */ bool qemu_in_iothread(void); +void iothread_ref(IOThread *iothread, const IOThreadHolder *holder); +void iothread_unref(IOThread *iothread, const IOThreadHolder *holder); + #endif /* IOTHREAD_H */ diff --git a/iothread.c b/iothread.c index 3558535b40..66dfde626e 100644 --- a/iothread.c +++ b/iothread.c @@ -21,10 +21,71 @@ #include "system/iothread.h" #include "qapi/error.h" #include "qapi/qapi-commands-misc.h" +#include "qapi/clone-visitor.h" +#include "qapi/qapi-visit-misc.h" #include "qemu/error-report.h" #include "qemu/rcu.h" #include "qemu/main-loop.h" +/* Add a deep copy of @holder to @iothread's list of holders. */ +void iothread_ref(IOThread *iothread, const IOThreadHolder *holder) +{ + assert(holder); + + QAPI_LIST_PREPEND(iothread->holders, QAPI_CLONE(IOThreadHolder, holder)); +} + +static int iothread_holder_compare(const IOThreadHolder *holder_a, + const IOThreadHolder *holder_b) +{ + const char *name_a, *name_b; + + if (holder_a->type != holder_b->type) { + return holder_a->type - holder_b->type; + } + + switch (holder_a->type) { + case IO_THREAD_HOLDER_KIND_QOM_OBJECT: + name_a = holder_a->u.qom_object.qom_path; + name_b = holder_b->u.qom_object.qom_path; + break; + case IO_THREAD_HOLDER_KIND_BLOCK_EXPORT: + name_a = holder_a->u.block_export.export_id; + name_b = holder_b->u.block_export.export_id; + break; + default: + g_assert_not_reached(); + } + + return strcmp(name_a, name_b); +} + +/* + * Remove @holder from @iothread's list of holders. + * + * It is a programming error if @holder is not present. + */ +void iothread_unref(IOThread *iothread, const IOThreadHolder *holder) +{ + IOThreadHolderList **prev = &iothread->holders; + IOThreadHolderList *curr; + + assert(holder); + + while (*prev) { + curr = *prev; + if (iothread_holder_compare(curr->value, holder) == 0) { + *prev = curr->next; + curr->next = NULL; + qapi_free_IOThreadHolderList(curr); + return; + } + prev = &curr->next; + } + + g_assert_not_reached(); +} + static void *iothread_run(void *opaque) { IOThread *iothread = opaque; @@ -129,6 +190,7 @@ static void iothread_instance_finalize(Object *obj) iothread->main_loop = NULL; } qemu_sem_destroy(&iothread->init_done_sem); + qapi_free_IOThreadHolderList(iothread->holders); } static void iothread_init_gcontext(IOThread *iothread, const char *thread_name) @@ -373,6 +435,7 @@ static int query_one_iothread(Object *object, void *opaque) info = g_new0(IOThreadInfo, 1); info->id = iothread_get_id(iothread); info->thread_id = iothread->thread_id; + info->holders = QAPI_CLONE(IOThreadHolderList, iothread->holders); info->poll_max_ns = iothread->poll_max_ns; info->poll_grow = iothread->poll_grow; info->poll_shrink = iothread->poll_shrink; diff --git a/qapi/misc.json b/qapi/misc.json index c71a5fe657..eb3b89293d 100644 --- a/qapi/misc.json +++ b/qapi/misc.json @@ -67,6 +67,55 @@ ## { 'command': 'query-name', 'returns': 'NameInfo', 'allow-preconfig': true } +## +# @IOThreadHolderBlockExport: +# +# @export-id: The unique block export identifier. +# +# Since: 11.2 +# +## +{ 'struct': 'IOThreadHolderBlockExport', + 'data': { 'export-id': 'str' } } + +## +# @IOThreadHolderQomObject: +# +# @qom-path: Path to the object in the QOM tree. +# +# Since: 11.2 +# +## +{ 'struct': 'IOThreadHolderQomObject', + 'data': { 'qom-path': 'str' } } + +## +# @IOThreadHolderKind: +# +# @block-export: A block export. +# @qom-object: A QOM object. +# +# Since: 11.2 +## +{ 'enum': 'IOThreadHolderKind', + 'data': [ 'block-export', 'qom-object' ] } + +## +# @IOThreadHolder: +# +# The block export or QOM object holding the iothread. +# +# @type: the kind of iothread holder. +# +# Since: 11.2 +## +{ 'union': 'IOThreadHolder', + 'base': { 'type': 'IOThreadHolderKind' }, + 'discriminator': 'type', + 'data': { + 'block-export': 'IOThreadHolderBlockExport', + 'qom-object': 'IOThreadHolderQomObject' } } + ## # @IOThreadInfo: # @@ -76,6 +125,10 @@ # # @thread-id: ID of the underlying host thread # +# @holders: the QOM objects or block exports currently holding this +# iothread. When a holder is detached or destroyed, it is removed +# from this list. (Since 11.2) +# # @poll-max-ns: maximum polling time in ns, 0 means polling is # disabled (since 2.9) # @@ -98,6 +151,7 @@ { 'struct': 'IOThreadInfo', 'data': {'id': 'str', 'thread-id': 'int', + 'holders': ['IOThreadHolder'], 'poll-max-ns': 'int', 'poll-grow': 'int', 'poll-shrink': 'int', @@ -122,20 +176,36 @@ # -> { "execute": "query-iothreads" } # <- { "return": [ # { -# "id":"iothread0", -# "thread-id":3134, -# "poll-max-ns":32768, -# "poll-grow":0, -# "poll-shrink":0, -# "aio-max-batch":0 +# "id": "iothread0", +# "thread-id": 3134, +# "holders": [ +# { +# "qom-path": "/machine/peripheral/blk1/virtio-backend", +# "type": "qom-object" +# }, +# { +# "qom-path": "/machine/peripheral/blk2/virtio-backend", +# "type": "qom-object" +# } +# ], +# "poll-max-ns": 32768, +# "poll-grow": 0, +# "poll-shrink": 0, +# "aio-max-batch": 0 # }, # { -# "id":"iothread1", -# "thread-id":3135, -# "poll-max-ns":32768, -# "poll-grow":0, -# "poll-shrink":0, -# "aio-max-batch":0 +# "id": "iothread1", +# "thread-id": 3135, +# "holders": [ +# { +# "export-id": "export0", +# "type": "block-export" +# } +# ], +# "poll-max-ns": 32768, +# "poll-grow": 0, +# "poll-shrink": 0, +# "aio-max-batch": 0 # } # ] # } -- 2.55.0