Re: [Qemu-devel] [PATCH RFC v3 0/7] qemu_thread_create: propagate errors to callers to check

[Peter Xu]

On Wed, Sep 19, 2018 at 09:35:16PM +0800, Fei Li wrote:
> Hi,
> 
> This idea comes from BiteSizedTasks, and this patch series implement
> the error checking of qemu_thread_create: make qemu_thread_create
> return a flag to indicate if it succeeded rather than failing with an
> error; make all callers check it.
> 
> The first three patches apply to those call traces whose further
> callers already have the *errp to pass, thus add a new Error paramater
> in the call trace to propagate the error and let the further caller
> check it. The last patch modifies the qemu_thread_create() and makes
> it return a bool to all direct callers to indicate if it succeeds.
> The middle three fix some segmentation fault when using GDB to debug.
> 
> ###### Here I have a concern about using multifd migration. ######
> It is about "[PATCH RFC v3 5/7] migration: fix the multifd code".
> In our current code, when multifd is used during migration, if there
> is an error before the destination receives all new channels (I mean
> multifd_recv_new_channel(ioc)), the destination does not exit but
> keeps waiting (Hang in recvmsg() in qio_channel_socket_readv) until
> the source exits. I know hang is not right, but so sorry that I did
> not come up with a good idea on handling this. Not so familiar with
> that part of code.. Could someone kindly give a hand? Thanks a lot!

CCing Juan for the multifd concerns.

Regards,

-- 
Peter Xu