Re: [Qemu-devel] [virtio-dev] Re: [PATCH v9 3/8] migration: use bitmap_mutex in migration_bitmap_clear_dirty

[Wei Wang]

On 11/27/2018 03:41 PM, Peter Xu wrote:
> Ok then I'm fine with it.  Though you could update the comments too if
> you like:
>
>      /* protects modification of the bitmap and migration_dirty_pages */
>      QemuMutex bitmap_mutex;
>
> And it's tricky that sometimes we don't take the lock when reading
> this variable "migration_dirty_pages".  I don't see obvious issue so
> far, hope it's true (at least I skipped the colo ones...).

The caller reads the value just to estimate the remaining_size, and
it seems fine without a lock, because whether it reads a
value before the update or after the update seem not causing
an issue.

Best,
Wei