Re: [Qemu-devel] [PATCH v4 12/12] migration: implement the shutdown for RDMA QIOChannel

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Lidong Chen (jemmy858585@gmail.com) wrote:
> Because RDMA QIOChannel not implement shutdown function,
> If the to_dst_file was set error, the return path thread
> will wait forever. and the migration thread will wait
> return path thread exit.
> 
> the backtrace of return path thread is:
> 
> (gdb) bt
>     #0  0x00007f372a76bb0f in ppoll () from /lib64/libc.so.6
>     #1  0x000000000071dc24 in qemu_poll_ns (fds=0x7ef7091d0580, nfds=2, timeout=100000000)
>         at qemu-timer.c:325
>     #2  0x00000000006b2fba in qemu_rdma_wait_comp_channel (rdma=0xd424000)
>         at migration/rdma.c:1501
>     #3  0x00000000006b3191 in qemu_rdma_block_for_wrid (rdma=0xd424000, wrid_requested=4000,
>         byte_len=0x7ef7091d0640) at migration/rdma.c:1580
>     #4  0x00000000006b3638 in qemu_rdma_exchange_get_response (rdma=0xd424000,
>         head=0x7ef7091d0720, expecting=3, idx=0) at migration/rdma.c:1726
>     #5  0x00000000006b3ad6 in qemu_rdma_exchange_recv (rdma=0xd424000, head=0x7ef7091d0720,
>         expecting=3) at migration/rdma.c:1903
>     #6  0x00000000006b5d03 in qemu_rdma_get_buffer (opaque=0x6a57dc0, buf=0x5c80030 "", pos=8,
>         size=32768) at migration/rdma.c:2714
>     #7  0x00000000006a9635 in qemu_fill_buffer (f=0x5c80000) at migration/qemu-file.c:232
>     #8  0x00000000006a9ecd in qemu_peek_byte (f=0x5c80000, offset=0)
>         at migration/qemu-file.c:502
>     #9  0x00000000006a9f1f in qemu_get_byte (f=0x5c80000) at migration/qemu-file.c:515
>     #10 0x00000000006aa162 in qemu_get_be16 (f=0x5c80000) at migration/qemu-file.c:591
>     #11 0x00000000006a46d3 in source_return_path_thread (
>         opaque=0xd826a0 <current_migration.37100>) at migration/migration.c:1331
>     #12 0x00007f372aa49e25 in start_thread () from /lib64/libpthread.so.0
>     #13 0x00007f372a77635d in clone () from /lib64/libc.so.6
> 
> the backtrace of migration thread is:
> 
> (gdb) bt
>     #0  0x00007f372aa4af57 in pthread_join () from /lib64/libpthread.so.0
>     #1  0x00000000007d5711 in qemu_thread_join (thread=0xd826f8 <current_migration.37100+88>)
>         at util/qemu-thread-posix.c:504
>     #2  0x00000000006a4bc5 in await_return_path_close_on_source (
>         ms=0xd826a0 <current_migration.37100>) at migration/migration.c:1460
>     #3  0x00000000006a53e4 in migration_completion (s=0xd826a0 <current_migration.37100>,
>         current_active_state=4, old_vm_running=0x7ef7089cf976, start_time=0x7ef7089cf980)
>         at migration/migration.c:1695
>     #4  0x00000000006a5c54 in migration_thread (opaque=0xd826a0 <current_migration.37100>)
>         at migration/migration.c:1837
>     #5  0x00007f372aa49e25 in start_thread () from /lib64/libpthread.so.0
>     #6  0x00007f372a77635d in clone () from /lib64/libc.so.6
> 
> Signed-off-by: Lidong Chen <lidongchen@tencent.com>

Yeh OK, this should help;  so:

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

I wonder if there are any places we can get stuck in rdma calls though where this isn't enough?

> ---
>  migration/rdma.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
> 
> diff --git a/migration/rdma.c b/migration/rdma.c
> index d611a06..0912b6a 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -3038,6 +3038,45 @@ static int qio_channel_rdma_close(QIOChannel *ioc,
>      return 0;
>  }
>  
> +static int
> +qio_channel_rdma_shutdown(QIOChannel *ioc,
> +                            QIOChannelShutdown how,
> +                            Error **errp)
> +{
> +    QIOChannelRDMA *rioc = QIO_CHANNEL_RDMA(ioc);
> +    RDMAContext *rdmain, *rdmaout;
> +
> +    rcu_read_lock();
> +
> +    rdmain = atomic_rcu_read(&rioc->rdmain);
> +    rdmaout = atomic_rcu_read(&rioc->rdmain);
> +
> +    switch (how) {
> +    case QIO_CHANNEL_SHUTDOWN_READ:
> +        if (rdmain) {
> +            rdmain->error_state = -1;
> +        }
> +        break;
> +    case QIO_CHANNEL_SHUTDOWN_WRITE:
> +        if (rdmaout) {
> +            rdmaout->error_state = -1;
> +        }
> +        break;
> +    case QIO_CHANNEL_SHUTDOWN_BOTH:
> +    default:
> +        if (rdmain) {
> +            rdmain->error_state = -1;
> +        }
> +        if (rdmaout) {
> +            rdmaout->error_state = -1;
> +        }
> +        break;
> +    }
> +
> +    rcu_read_unlock();
> +    return 0;
> +}
> +
>  /*
>   * Parameters:
>   *    @offset == 0 :
> @@ -3864,6 +3903,7 @@ static void qio_channel_rdma_class_init(ObjectClass *klass,
>      ioc_klass->io_close = qio_channel_rdma_close;
>      ioc_klass->io_create_watch = qio_channel_rdma_create_watch;
>      ioc_klass->io_set_aio_fd_handler = qio_channel_rdma_set_aio_fd_handler;
> +    ioc_klass->io_shutdown = qio_channel_rdma_shutdown;
>  }
>  
>  static const TypeInfo qio_channel_rdma_info = {
> -- 
> 1.8.3.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK