On Thu, 2014-11-20 at 19:25 +0800, Zhen Lei wrote: > The next code fragment "list_for_each_entry" is not depend on "minor". With > this > patch, the free of "minor" in "list_for_each_entry" can be reduced, and there > is > no functional change.
A reasonable micro-optimization, but I'm curious if you're actually seeing some measurable overhead from this. It seems like we'd need to have multiple devices, all within the same IOMMU group, all probed by vfio-pci at the same time to exercise the race condition. Thanks, Alex > Signed-off-by: Zhen Lei <[email protected]> > --- > drivers/vfio/vfio.c | 13 ++++++------- > 1 file changed, 6 insertions(+), 7 deletions(-) > > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c > index f018d8d..737eb468 100644 > --- a/drivers/vfio/vfio.c > +++ b/drivers/vfio/vfio.c > @@ -225,22 +225,21 @@ static struct vfio_group *vfio_create_group(struct > iommu_group *iommu_group) > > mutex_lock(&vfio.group_lock); > > - minor = vfio_alloc_group_minor(group); > - if (minor < 0) { > - vfio_group_unlock_and_free(group); > - return ERR_PTR(minor); > - } > - > /* Did we race creating this group? */ > list_for_each_entry(tmp, &vfio.group_list, vfio_next) { > if (tmp->iommu_group == iommu_group) { > vfio_group_get(tmp); > - vfio_free_group_minor(minor); > vfio_group_unlock_and_free(group); > return tmp; > } > } > > + minor = vfio_alloc_group_minor(group); > + if (minor < 0) { > + vfio_group_unlock_and_free(group); > + return ERR_PTR(minor); > + } > + > dev = device_create(vfio.class, NULL, > MKDEV(MAJOR(vfio.group_devt), minor), > group, "%d", iommu_group_id(iommu_group)); > -- > 1.8.0 > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
