Re: [Qemu-devel] [PATCH] dump: Acquire BQL around vm_start() in dump thread

[Paolo Bonzini <pbonzini@redhat.com>]

On 03/05/2017 09:28, Fam Zheng wrote:
> This fixes an assertion failure in the following backtrace:
> 
>     __GI___assert_fail
>     memory_region_transaction_commit
>     memory_region_add_eventfd
>     virtio_pci_ioeventfd_assign
>     virtio_bus_set_host_notifier
>     virtio_blk_data_plane_start
>     virtio_bus_start_ioeventfd
>     virtio_vmstate_change
>     vm_state_notify
>     vm_prepare_start
>     vm_start
>     dump_cleanup
>     dump_process
>     dump_thread
>     start_thread
>     clone
> 
> vm_start need BQL, acquire it if doing cleaning up from main thread.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  dump.c                | 7 +++++++
>  include/sysemu/dump.h | 1 +
>  2 files changed, 8 insertions(+)
> 
> diff --git a/dump.c b/dump.c
> index f7b80d8..d9090a2 100644
> --- a/dump.c
> +++ b/dump.c
> @@ -77,7 +77,13 @@ static int dump_cleanup(DumpState *s)
>      memory_mapping_list_free(&s->list);
>      close(s->fd);
>      if (s->resume) {
> +        if (s->detached) {
> +            qemu_mutex_lock_iothread();
> +        }
>          vm_start();
> +        if (s->detached) {
> +            qemu_mutex_unlock_iothread();
> +        }
>      }
>  
>      return 0;
> @@ -1804,6 +1810,7 @@ void qmp_dump_guest_memory(bool paging, const char *file,
>  
>      if (detach_p) {
>          /* detached dump */
> +        s->detached = true;
>          qemu_thread_create(&s->dump_thread, "dump_thread", dump_thread,
>                             s, QEMU_THREAD_DETACHED);
>      } else {
> diff --git a/include/sysemu/dump.h b/include/sysemu/dump.h
> index ef931be..2672a15 100644
> --- a/include/sysemu/dump.h
> +++ b/include/sysemu/dump.h
> @@ -157,6 +157,7 @@ typedef struct DumpState {
>      uint32_t sh_info;
>      bool have_section;
>      bool resume;
> +    bool detached;
>      ssize_t note_size;
>      hwaddr memory_offset;
>      int fd;
> 

Queued, thanks.

Paolo