On Sun, Sep 06, 2015 at 06:53:00PM +1000, Dave Airlie wrote:
> There is a race where the reply could get processed by another
> work queue before we've updated the state.
>
> Update the state before sending the msg to close it.
>
> v2: reset value if return indicates we haven't send the msg.
>
> Pointed out by Adam J Richter on
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91481
> Signed-off-by: Dave Airlie <airlied at redhat.com>
Ok we see to have two callers of drm_dp_send_link_address:
- drm_dp_add_port, but the only caller of that in turn is again
drm_dp_send_link_address. This is just self-recursion.
- drm_dp_check_and_send_link_address, which in turn is called only by
itself and by drm_dp_mst_link_probe_work.
drm_dp_mst_link_probe_work is only called from the mgr->work function, and
a single work item is never run concurrently.
I don't see any race here at all. A good cleanup though would be what
Adam's original patch has done and move the link_address_sent = true into
drm_dp_send_link_address.
Cheers, Daniel
> ---
> drivers/gpu/drm/drm_dp_mst_topology.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 294d904..831096b9 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -1101,8 +1101,10 @@ static void drm_dp_add_port(struct drm_dp_mst_branch
> *mstb,
>
> ret = drm_dp_port_setup_pdt(port);
> if (ret == true) {
> - drm_dp_send_link_address(mstb->mgr, port->mstb);
> port->mstb->link_address_sent = true;
> + ret = drm_dp_send_link_address(mstb->mgr, port->mstb);
> + if (ret < 0)
> + port->mstb->link_address_sent = false;
> }
> }
>
> @@ -1198,8 +1200,11 @@ static void drm_dp_check_and_send_link_address(struct
> drm_dp_mst_topology_mgr *m
> struct drm_dp_mst_port *port;
> struct drm_dp_mst_branch *mstb_child;
> if (!mstb->link_address_sent) {
> - drm_dp_send_link_address(mgr, mstb);
> + int ret;
> mstb->link_address_sent = true;
> + ret = drm_dp_send_link_address(mgr, mstb);
> + if (ret < 0)
> + mstb->link_address_sent = false;
> }
> list_for_each_entry(port, &mstb->ports, next) {
> if (port->input)
> @@ -1493,11 +1498,12 @@ static int drm_dp_send_link_address(struct
> drm_dp_mst_topology_mgr *mgr,
> }
> (*mgr->cbs->hotplug)(mgr);
> }
> + ret = 0;
> } else
> DRM_DEBUG_KMS("link address failed %d\n", ret);
>
> kfree(txmsg);
> - return 0;
> + return ret;
> }
>
> static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr
> *mgr,
> --
> 2.4.3
>
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> dri-devel at lists.freedesktop.org
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
