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Re: [Qemu-devel] [PATCH 7/9] block-migration: remove not needed iothread
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 7/9] block-migration: remove not needed iothread lock |
Date: |
Thu, 08 Jan 2015 23:28:47 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 |
On 11/12/2014 15:17, Vladimir Sementsov-Ogievskiy wrote:
> - qemu_mutex_lock_iothread();
> + bdrv_reset_dirty_bitmap(bs, bmds->dirty_bitmap, cur_sector, nr_sectors);
> +
> blk->aiocb = bdrv_aio_readv(bs, cur_sector, &blk->qiov,
> nr_sectors, blk_mig_read_cb, blk);
>
> - bdrv_reset_dirty_bitmap(bs, bmds->dirty_bitmap, cur_sector, nr_sectors);
> - qemu_mutex_unlock_iothread();
> -
bdrv_aio_readv is not thread safe, so it needs the iothread lock.
bdrv_reset_dirty_bitmap is also not thread safe, because
bmds->dirty_bitmap is accessed concurrently by bdrv_reset_dirty
(discard) and bdrv_set_dirty (write). So it needs the iothread lock too.
Moving bdrv_reset_dirty_bitmap before the read is a good idea.
Paolo
- Re: [Qemu-devel] [PATCH 7/9] block-migration: remove not needed iothread lock,
Paolo Bonzini <=