On Fri, Jun 26, 2026 at 4:46 PM Markus Armbruster <[email protected]> wrote: > > Looks like you missed my review of v8. I'm replaying my review > comments.
Oh, my fault, very sorry about that, focused on other patch's comments fixes. Thank you for your detailed explanation. I will address your comments in next version. Expect the: IOThreadHolder *h = QAPI_CLONE(IOThreadHolder, holder); Same as your estimate, this doesn't seem worthwhile. And the same issue in the [ PATCH V8 14/15] comments: static IOThreadHolderList *iothread_get_holders_list(IOThread *iothread) > If iothread->holders was a IOThreadHolderList instead of a GList, this > loop could be QAPI_CLONE(IOThreadHolderList, iothread->holders) instead. If we change the GList *holders to the IOThreadHolderList *holders, This means that we have to reimplement the GList related API, for example the "g_list_prepend", "g_list_find_custom" and the "g_list_delete_link" This doesn't seem worthwhile. Thanks Chen > > Zhang Chen <[email protected]> writes: > > > Currently, IOThreads do not maintain a record of which devices are > > associated with them. This makes it difficult to monitor the > > workload distribution of IOThreads, especially in complex > > hotplug scenarios involving multiple virtio-blk or virtio-scsi devices. > > > > This patch introduces a reference counting and tracking mechanism > > within the IOThread object: > > > > - iothread_ref(): Prepends the device's IOThreadHolder to a list. > > - iothread_unref(): Searches for the IOThreadHolder using a custom > > string comparison (g_strcmp0), releases the associated memory > > upon a successful match. > > - holders: A GList storing the IOThreadHolder of attached devices > > for runtime introspection. > > > > A later commit will add QMP commands to let management applications > > query the attachment status of IOThreads. > > > > Signed-off-by: Zhang Chen <[email protected]> > > --- > > include/system/iothread.h | 5 +++ > > iothread.c | 94 +++++++++++++++++++++++++++++++++++++++ > > qapi/misc.json | 61 +++++++++++++++++++++++++ > > 3 files changed, 160 insertions(+) > > > > diff --git a/include/system/iothread.h b/include/system/iothread.h > > index a1ef7696cb..b9207ad829 100644 > > --- a/include/system/iothread.h > > +++ b/include/system/iothread.h > > @@ -50,6 +50,11 @@ struct IOThread { > > bool stopping; /* has iothread_stop() been called? */ > > bool running; /* should iothread_run() continue? */ > > int thread_id; > > + /* > > + * The list elements are of type IOThreadHolder, which can > > + * represent either a QOM path or a block node name. > > + */ > > You forgot monitors. Stefan spotted this as well, and I agree with the > fix he suggested. Yes, my fault. will fix in the next version. > > > + GList *holders; > > > > /* AioContext poll parameters */ > > int64_t poll_max_ns; > > diff --git a/iothread.c b/iothread.c > > index 3558535b40..3301b8d495 100644 > > --- a/iothread.c > > +++ b/iothread.c > > @@ -25,6 +25,92 @@ > > #include "qemu/rcu.h" > > #include "qemu/main-loop.h" > > > > +/* > > + * iothread_ref: > > + * @iothread: the iothread to track > > + * @holder: the IOThreadHolder object initialized by the caller > > + * > > + * Add the @holder to the iothread's tracking list. > > + */ > > +static void iothread_ref(IOThread *iothread, const IOThreadHolder *holder) > > +{ > > + assert(holder); > > + IOThreadHolder *h = g_new0(IOThreadHolder, 1); > > + > > + h->type = holder->type; > > + switch (holder->type) { > > + case IO_THREAD_HOLDER_KIND_QOM_OBJECT: > > + h->u.qom_object.qom_path = g_strdup(holder->u.qom_object.qom_path); > > + break; > > + case IO_THREAD_HOLDER_KIND_BLOCK_NODE: > > + h->u.block_node.node_name = > > + g_strdup(holder->u.block_node.node_name); > > + break; > > + case IO_THREAD_HOLDER_KIND_MONITOR_NAME: > > + h->u.monitor_name.monitor_name = > > + g_strdup(holder->u.monitor_name.monitor_name); > > + break; > > + default: > > + g_assert_not_reached(); > > + } > > This makes @h a deep copy of @holder. Try > > IOThreadHolder *h = QAPI_CLONE(IOThreadHolder, holder); > > instead. > > Instead of making a copy, the function could take ownership of @holder, > and require @holder's members to be dynamically allocated. More > efficient, but complicates the callers somewhat. Not worthwhile, I > guess. Yes, I > > > + > > + iothread->holders = g_list_prepend(iothread->holders, h); > > +} > > + > > +static int iothread_holder_compare(gconstpointer a, gconstpointer b) > > +{ > > + const IOThreadHolder *holder_a = a; > > + const IOThreadHolder *holder_b = b; > > + const char *name_a, *name_b; > > + > > + if (holder_a->type != holder_b->type) { > > + return -1; > > Please use > > return holder_b->type - holder_a->type; > > Why? By convention, an int-valued function fn() comparing A to B > returns less than 0 when A<B, 0 when A == B, and greater than 0 when > A>B. Anything else needs a prominent comment. Best to stick to the > convention whenever practical. > > Since A < B iff B > A, we want fn(A, B) == -fn(B, A). > > Your function does not satisfy that! Harmless for now, because you only > ever pass it to g_list_find_custom(), which treats all non-zero values > the same. But if anyone passes it to something like qsort() in the > future, they can look forward to some debugging "fun". > > > + } > > + > > + 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_NODE: > > + name_a = holder_a->u.block_node.node_name; > > + name_b = holder_b->u.block_node.node_name; > > + break; > > + case IO_THREAD_HOLDER_KIND_MONITOR_NAME: > > + name_a = holder_a->u.monitor_name.monitor_name; > > + name_b = holder_b->u.monitor_name.monitor_name; > > + break; > > + default: > > + /* > > + * This should not happen. If it does, name_a/b remains > > + * NULL and g_strcmp0 will handle it safely. > > + */ > > + name_a = NULL; > > + name_b = NULL; > > Replace this by > > g_assert_not_reached(); > > Then neither @name_a nor @name_b can be null, because a non-optional > QAPI str is never null. Simply use strcmp(). > > > + } > > + > > + return g_strcmp0(name_a, name_b); > > +} > > + > > +/* > > + * This function removes the @holder from the @iothread's tracking list. > > + * The @holder must match the one used previously in iothread_ref(). > > + * It is a programming error to call this with a @holder that is not > > + * currently associated with the @iothread. > > + */ > > +static void iothread_unref(IOThread *iothread, const IOThreadHolder > > *holder) > > +{ > > + assert(holder); > > + GList *link = g_list_find_custom(iothread->holders, holder, > > + > > (GCompareFunc)iothread_holder_compare); > > + > > + assert(link); > > + > > + IOThreadHolder *h = (IOThreadHolder *)link->data; > > + qapi_free_IOThreadHolder(h); > > + iothread->holders = g_list_delete_link(iothread->holders, link); > > Removing @link from the list before freeing link->data would be more > obviously correct, wouldn't it? > > > +} > > + > > static void *iothread_run(void *opaque) > > { > > IOThread *iothread = opaque; > > @@ -356,6 +442,14 @@ char *iothread_get_id(IOThread *iothread) > > > > AioContext *iothread_get_aio_context(IOThread *iothread) > > { > > + /* Remove in next patch for build */ > > + IOThreadHolder holder = { > > + .type = IO_THREAD_HOLDER_KIND_QOM_OBJECT, > > + .u.qom_object.qom_path = (char *)"tmp_path", > > + }; > > + iothread_ref(iothread, &holder); > > + iothread_unref(iothread, &holder); > > Is this really needed to make this patch work? > > > + > > return iothread->ctx; > > } > > > > diff --git a/qapi/misc.json b/qapi/misc.json > > index c71a5fe657..d9f82f0922 100644 > > --- a/qapi/misc.json > > +++ b/qapi/misc.json > > @@ -67,6 +67,67 @@ > > ## > > { 'command': 'query-name', 'returns': 'NameInfo', 'allow-preconfig': true } > > > > + > > +## > > +# @IOThreadHolderBlockNode: > > +# > > +# @node-name: A block node. > > Let's use > > # @node-name: Name of the block node > > to make it more similar to node-name descriptions elsewhere. > > > +# > > +# Since: 11.1 > > +# > > +## > > +{ 'struct': 'IOThreadHolderBlockNode', > > + 'data': { 'node-name': 'str' } } > > + > > +## > > +# @IOThreadHolderQomObject: > > +# > > +# @qom-path: A QOM Object. > > Likewise, let's use > > # @qom-path: Path to the object in the QOM tree > > > +# > > +# Since: 11.1 > > +# > > +## > > +{ 'struct': 'IOThreadHolderQomObject', > > + 'data': { 'qom-path': 'str' } } > > + > > +## > > +# @IOThreadHolderMonitor: > > +# > > +# @monitor-name: A HMP/QMP monitor. > > Let's use > > # @monitor-name: Name of the HMP/QMP monitor > > > +# > > +# Since: 11.1 > > +# > > +## > > +{ 'struct': 'IOThreadHolderMonitor', > > + 'data': { 'monitor-name': 'str' } } > > + > > +## > > +# @IOThreadHolderKind: > > +# > > +# @block-node: A block node. > > +# @qom-object: A QOM Object. > > +# @monitor-name: A HMP/QMP monitor. > > Rename to @monitor for consistency with the other two. > > Remark, not a request to change anything in your patch: kind monitor > will become obsolete when monitors become QOM objects. Doing that > before we release this interface is desirable. > > > +# > > +# Since: 11.1 > > +## > > +{ 'enum': 'IOThreadHolderKind', > > + 'data': [ 'block-node', 'qom-object', 'monitor-name' ] } > > + > > +## > > +# @IOThreadHolder: > > +# > > Let's add a short description: > > # The block node, QOM object, or monitor holding the I/O thread. > > > +# @type: the kind of I/O thread holder. > > +# > > +# Since: 11.1 > > +## > > +{ 'union': 'IOThreadHolder', > > + 'base': { 'type': 'IOThreadHolderKind' }, > > + 'discriminator': 'type', > > + 'data': { > > + 'block-node': 'IOThreadHolderBlockNode', > > + 'qom-object': 'IOThreadHolderQomObject', > > + 'monitor-name': 'IOThreadHolderMonitor' } } > > + > > ## > > # @IOThreadInfo: > > # >
