Re: Should I delete created coroutines manually?

[Coiby Xu]

On Tue, Aug 18, 2020 at 04:19:58PM +0100, Stefan Hajnoczi wrote:
> On Mon, Aug 17, 2020 at 2:13 PM Coiby Xu <coiby.xu@gmail.com> wrote:
> > I'm working on vhost-user block device backend [1]. When I tested my
> > patches on the latest version of QEMU (commit
> > d0ed6a69d399ae193959225cdeaa9382746c91cc) with --enable-sanitizer turned
> > on, the follow error will be thrown out,
> >
> >      ==46631==ERROR: LeakSanitizer: detected memory leaks
> >
> >      Direct leak of 312 byte(s) in 1 object(s) allocated from:
> >          #0 0x55d0a7813921 in calloc (qemu/qemu-storage-daemon+0x646921)
> >          #1 0x7f8bd6f7b591 in g_malloc0 (/usr/lib/libglib-2.0.so.0+0x4f591)
> >          #2 0x55d0a815f3fb in qemu_coroutine_create 
> > qemu/util/qemu-coroutine.c:75:14
> >          #3 0x55d0a817321e in vu_client_start 
> > qemu/util/vhost-user-server.c:225:23
> >          #4 0x55d0a816fcf3 in vu_accept qemu/util/vhost-user-server.c:341:5
> >          #5 0x55d0a7f1293f in qio_net_listener_channel_func 
> > qemu/io/net-listener.c:54:9
> >          #6 0x55d0a7efb0f3 in qio_channel_fd_source_dispatch 
> > qemu/io/channel-watch.c:84:12
> >          #7 0x7f8bd6f7e33f in g_main_context_dispatch 
> > (/usr/lib/libglib-2.0.so.0+0x5233f)
> >
> > I have to call qemu_coroutine_delete to eliminate this kind of errors.
>
> qemu_coroutine_delete() is an internal API and shouldn't be called directly.
>
> If you are sure that the coroutine terminated (returned from its entry
> function) then the leak is probably caused by the following:

Thank you for this clue! Yesterday I realized the execution of coroutine
has been yielded since qio_channel_yield is called. Now I give the socket
server enough time to do the clean-up work after the client socket is
closed and the issue is gone.

> util/qemu-coroutine.c has a pool of Coroutine objects that are reused.
> It's likely that the "leaked" object is in that pool.
>
> I'm surprised that this issue hasn't been reported before, but
> release_pool should be cleaned up when the program terminates.

I still can't figure out why the issue hasn't been reported before. I guess
I have to put it aside.
> Stefan

--
Best regards,
Coiby