On Tue, Mar 12, 2013 at 09:26:18AM +0100, Paolo Bonzini wrote:
> Il 12/03/2013 03:42, Asias He ha scritto:
> > This helper is useful to check if vs->vs_endpoint is setup by
> > vhost_scsi_set_endpoint()
> >
> > Signed-off-by: Asias He <as...@redhat.com>
> > Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
> > ---
> > drivers/vhost/tcm_vhost.c | 12 ++++++++++++
> > 1 file changed, 12 insertions(+)
> >
> > diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
> > index b3e50d7..29612bc 100644
> > --- a/drivers/vhost/tcm_vhost.c
> > +++ b/drivers/vhost/tcm_vhost.c
> > @@ -91,6 +91,18 @@ static int iov_num_pages(struct iovec *iov)
> > ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT;
> > }
> >
> > +static bool tcm_vhost_check_endpoint(struct vhost_scsi *vs)
> > +{
> > + bool ret = false;
> > +
> > + mutex_lock(&vs->dev.mutex);
> > + if (vs->vs_endpoint)
> > + ret = true;
> > + mutex_unlock(&vs->dev.mutex);
>
> The return value is invalid as soon as mutex_unlock is called, i.e.
> before tcm_vhost_check_endpoint returns. Instead, check vs->vs_endpoint
> in the caller while the mutex is taken.
Do you mean 1) or 2)?
1)
vhost_scsi_handle_vq()
{
mutex_lock(&vs->dev.mutex);
check vs->vs_endpoint
mutex_unlock(&vs->dev.mutex);
handle vq
}
2)
vhost_scsi_handle_vq()
{
lock vs->dev.mutex
check vs->vs_endpoint
handle vq
unlock vs->dev.mutex
}
1) does not make any difference with the original
one right?
2) would be too heavy. This might not be a problem in current 1 thread
per vhost model. But if we want concurrent multiqueue, this will be
killing us.
Anyway, the current one is not good. Need to think.
> Paolo
>
> > + return ret;
> > +}
> > +
> > static int tcm_vhost_check_true(struct se_portal_group *se_tpg)
> > {
> > return 1;
> >
>
--
Asias
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