On Tue, Aug 11, 2026 at 04:51:55PM +0800, Zhang Chen wrote: > On Fri, Aug 7, 2026 at 9:41 PM Markus Armbruster <[email protected]> wrote: > > > > Zhang Chen <[email protected]> writes: > > > > > Introduce iothread_ref_and_get_aio_context() with a holder argument > > > and its counterpart iothread_put_aio_context(). > > > > > > Previously, users of an IOThread AioContext did not explicitly record > > > their identity, making it difficult to debug which devices or > > > subsystems were pinning an IOThread. > > > > > > Registering a holder takes an IOThread object reference so that the > > > IOThread and its AioContext stay alive until the matching put > > > operation. Document the ownership and BQL requirements. > > > > > > Signed-off-by: Zhang Chen <[email protected]> > > > --- > > > include/system/iothread.h | 21 +++++++++++++++++++++ > > > iothread.c | 23 ++++++++++++++++++++++- > > > 2 files changed, 43 insertions(+), 1 deletion(-) > > > > > > diff --git a/include/system/iothread.h b/include/system/iothread.h > > > index b8aeb32b0e..b6664e7a38 100644 > > > --- a/include/system/iothread.h > > > +++ b/include/system/iothread.h > > > @@ -67,6 +67,27 @@ DECLARE_INSTANCE_CHECKER(IOThread, IOTHREAD, > > > char *iothread_get_id(IOThread *iothread); > > > IOThread *iothread_by_id(const char *id); > > > AioContext *iothread_get_aio_context(IOThread *iothread); > > > + > > > +/* > > > + * Register @holder and return @iothread's AioContext. The holder is > > > copied, > > > + * and a reference is taken on @iothread so that both the IOThread and > > > its > > > + * AioContext remain alive. > > > + * > > > + * The caller must eventually call iothread_put_aio_context() with an > > > + * equivalent holder. This function is not thread-safe and must be > > > called > > > + * under the Big QEMU Lock (BQL). > > > + */ > > > +AioContext *iothread_ref_and_get_aio_context(IOThread *iothread, > > > + const IOThreadHolder > > > *holder); > > > + > > > +/* > > > + * Unregister @holder and release the corresponding reference on > > > @iothread. > > > + * Calling this function without a matching > > > + * iothread_ref_and_get_aio_context() call is a programming error. > > > + * > > > + * This function is not thread-safe and must be called under the BQL. > > > + */ > > > +void iothread_put_aio_context(IOThread *iothread, const IOThreadHolder > > > *holder); > > > GMainContext *iothread_get_g_main_context(IOThread *iothread); > > > > > > /* > > > diff --git a/iothread.c b/iothread.c > > > index 2a4c92e08b..0cc8344ee6 100644 > > > --- a/iothread.c > > > +++ b/iothread.c > > > @@ -33,6 +33,11 @@ void iothread_ref(IOThread *iothread, const > > > IOThreadHolder *holder) > > > assert(holder); > > > > > > QAPI_LIST_PREPEND(iothread->holders, QAPI_CLONE(IOThreadHolder, > > > holder)); > > > + /* > > > + * This guarantees that the IOThread and its AioContext remain alive > > > + * as long as there is a holder. > > > + */ > > > + object_ref(OBJECT(iothread)); > > > } > > > > > > static int iothread_holder_compare(const IOThreadHolder *holder_a, > > > @@ -78,6 +83,7 @@ void iothread_unref(IOThread *iothread, const > > > IOThreadHolder *holder) > > > *prev = curr->next; > > > curr->next = NULL; > > > qapi_free_IOThreadHolderList(curr); > > > + object_unref(OBJECT(iothread)); > > > return; > > > } > > > prev = &curr->next; > > > @@ -199,7 +205,7 @@ static void iothread_init_gcontext(IOThread > > > *iothread, const char *thread_name) > > > g_autofree char *name = g_strdup_printf("%s aio-context", > > > thread_name); > > > > > > iothread->worker_context = g_main_context_new(); > > > - source = aio_get_g_source(iothread_get_aio_context(iothread)); > > > + source = aio_get_g_source(iothread->ctx); > > > g_source_set_name(source, name); > > > g_source_attach(source, iothread->worker_context); > > > g_source_unref(source); > > > @@ -421,6 +427,21 @@ AioContext *iothread_get_aio_context(IOThread > > > *iothread) > > > return iothread->ctx; > > > } > > > > > > +AioContext *iothread_ref_and_get_aio_context(IOThread *iothread, > > > + const IOThreadHolder > > > *holder) > > > +{ > > > + /* Add IOThreadHolder to the list */ > > > + iothread_ref(iothread, holder); > > > + > > > + return iothread->ctx; > > > +} > > > + > > > +void iothread_put_aio_context(IOThread *iothread, const IOThreadHolder > > > *holder) > > > > Should we name this "unref" rather than "put"? Perhaps Stefan has an > > opinion. > > It's OK for me. The original code was designed to match the > "iothread_get_aio_context", > If Stefan has no objection， I will change the name to > "iothread_unref_aio_context".
iothread_unref_and_put_aio_context() would be consistent with
iothread_ref_and_get_aio_context() :)
Stefan
>
> Thanks
>
> Chen
>
> >
> > > +{
> > > + /* Delete IOThreadHolder from the list */
> > > + iothread_unref(iothread, holder);
> > > +}
> > > +
> > > static int query_one_iothread(Object *object, void *opaque)
> > > {
> > > IOThreadInfoList ***tail = opaque;
> >
>
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