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Subject: Re: [PATCH v22 2/3] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ
On 01/18/2018 12:44 AM, Michael S. Tsirkin wrote:
On Wed, Jan 17, 2018 at 01:10:11PM +0800, Wei Wang wrote:+static void virtballoon_changed(struct virtio_device *vdev)+{ + struct virtio_balloon *vb = vdev->priv; + unsigned long flags; + __u32 cmd_id; + s64 diff = towards_target(vb); + + if (diff) { + spin_lock_irqsave(&vb->stop_update_lock, flags); + if (!vb->stop_update)Why do you ignore stop_update for freeze? This means new wq entries can be added during remove causing use after free issues.
I think stop_update isn't needed, because the lock has already been handled internally by the APIs. Similar examples like mem_cgroup_css_free() in "mm/memcontrol.c", there is no such locks used for cancel_work_sync(&memcg->high_work).
Best, Wei
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