Re: [Qemu-devel] [PATCH 05/27] block/parallels: add get_block_status

[Stefan Hajnoczi]

On Wed, Mar 11, 2015 at 01:27:59PM +0300, Denis V. Lunev wrote:
> +static int64_t coroutine_fn parallels_co_get_block_status(BlockDriverState 
> *bs,
> +        int64_t sector_num, int nb_sectors, int *pnum)
> +{
> +    BDRVParallelsState *s = bs->opaque;
> +    int64_t offset;
> +
> +    qemu_co_mutex_lock(&s->lock);
> +    offset = seek_to_sector(s, sector_num);
> +    qemu_co_mutex_unlock(&s->lock);

The lock isn't necessary here yet.  It may become necessary when write
support is added, but probably not even then since seek_to_sector()
cannot yield (it's not a coroutine function), so there are no possible
races with other coroutines.

The same also applies for parallels_co_read().  The lock there isn't
necessary since the block driver is read-only and has no mutable state -
there is no shared state that needs lock protection.

pgpkQMnxzQipW.pgp
Description: PGP signature