Il 09/11/2012 07:29, Nicholas A. Bellinger ha scritto: > From: Nicholas Bellinger <n...@linux-iscsi.org> > > This patch fixes a regression bug in virtscsi_kick_cmd() that relinquishes > the acquired spinlocks in the incorrect order using the wrong spin_unlock > macros, namely releasing vq->vq_lock before tgt->tgt_lock while invoking > the calls to virtio_ring.c:virtqueue_add_buf() and friends. > > This bug was originally introduced in v3.5-rc7 code with: > > commit 2bd37f0fde99cbf8b78fb55f1128e8c3a63cf1da > Author: Paolo Bonzini <pbonz...@redhat.com> > Date: Wed Jun 13 16:56:34 2012 +0200 > > [SCSI] virtio-scsi: split scatterlist per target > > Go ahead and make sure that vq->vq_lock is relinquished w/ spin_unlock > first, then release tgt->tgt_lock w/ spin_unlock_irqrestore.
That's done on purpose. After you do virtqueue_add_buf, you don't need the sg list anymore, nor the lock that protects it. The cover letter is at https://lkml.org/lkml/2012/6/13/295 and had this text: This series reorganizes the locking in virtio-scsi, introducing separate scatterlists for each target and "pipelining" the locks so that one command can be queued while the other is prepared. This improves performance when there are multiple in-flight operations. In fact, the patch _introduces_ wrong locking because virtqueue_kick_prepare needs the vq_lock. Perhaps what you want is separate local_irq_save/local_irq_restore? Paolo > Cc: Paolo Bonzini <pbonz...@redhat.com> > Cc: James Bottomley <jbottom...@parallels.com> > Cc: Christoph Hellwig <h...@lst.de> > Cc: sta...@vger.kernel.org > Signed-off-by: Nicholas Bellinger <n...@linux-iscsi.org> > --- > drivers/scsi/virtio_scsi.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c > index 595af1a..b2abb8a 100644 > --- a/drivers/scsi/virtio_scsi.c > +++ b/drivers/scsi/virtio_scsi.c > @@ -417,11 +417,11 @@ static int virtscsi_kick_cmd(struct > virtio_scsi_target_state *tgt, > > spin_lock(&vq->vq_lock); > ret = virtqueue_add_buf(vq->vq, tgt->sg, out_num, in_num, cmd, gfp); > - spin_unlock(&tgt->tgt_lock); > + spin_unlock(&vq->vq_lock); > if (ret >= 0) > ret = virtqueue_kick_prepare(vq->vq); > > - spin_unlock_irqrestore(&vq->vq_lock, flags); > + spin_unlock_irqrestore(&tgt->tgt_lock, flags); > > if (ret > 0) > virtqueue_notify(vq->vq); > -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
