search for: drm_dp_mst_topology_try_get_mstb

..._dp_mst_topology.c :export: +Topology Lifetime Internals +--------------------------- + +These functions aren't exported to drivers, but are documented here to help make +the MST topology helpers easier to understand + +.. kernel-doc:: drivers/gpu/drm/drm_dp_mst_topology.c + :functions: drm_dp_mst_topology_try_get_mstb drm_dp_mst_topology_get_mstb + drm_dp_mst_topology_put_mstb + drm_dp_mst_topology_try_get_port drm_dp_mst_topology_get_port + drm_dp_mst_topology_put_port + drm_dp_mst_get_mstb_malloc drm_dp_mst_put_mstb_malloc + MIPI DSI Helper Functions Ref...

..._dp_mst_topology.c :export: +Topology Lifetime Internals +--------------------------- + +These functions aren't exported to drivers, but are documented here to help make +the MST topology helpers easier to understand + +.. kernel-doc:: drivers/gpu/drm/drm_dp_mst_topology.c + :functions: drm_dp_mst_topology_try_get_mstb drm_dp_mst_topology_get_mstb + drm_dp_mst_topology_put_mstb + drm_dp_mst_topology_try_get_port drm_dp_mst_topology_get_port + drm_dp_mst_topology_put_port + drm_dp_mst_get_mstb_malloc drm_dp_mst_put_mstb_malloc + MIPI DSI Helper Functions Ref...

...st_branch *rmstb = NULL; struct drm_dp_mst_port *found_port; + mutex_lock(&mgr->lock); - if (mgr->mst_primary) { + if (!mgr->mst_primary) + goto out; + + do { found_port = drm_dp_get_last_connected_port_to_mstb(mstb); + if (!found_port) + break; - if (found_port) { + if (drm_dp_mst_topology_try_get_mstb(found_port->parent)) { rmstb = found_port->parent; - if (drm_dp_mst_topology_try_get_mstb(rmstb)) { - *port_num = found_port->port_num; - } else { - rmstb = NULL; - } + *port_num = found_port->port_num; + } else { + /* Search again, starting from this parent */ +...

...st_branch *rmstb = NULL; struct drm_dp_mst_port *found_port; + mutex_lock(&mgr->lock); - if (mgr->mst_primary) { + if (!mgr->mst_primary) + goto out; + + do { found_port = drm_dp_get_last_connected_port_to_mstb(mstb); + if (!found_port) + break; - if (found_port) { + if (drm_dp_mst_topology_try_get_mstb(found_port->parent)) { rmstb = found_port->parent; - if (drm_dp_mst_topology_try_get_mstb(rmstb)) - *port_num = found_port->port_num; - else - rmstb = NULL; + *port_num = found_port->port_num; + } else { + /* Search again, starting from this parent */ + mstb = found...

This is the series I've been working on for a while now to get all of the atomic DRM drivers in the tree to use the atomic MST helpers, and to make the atomic MST helpers actually idempotent. Turns out it's a lot more difficult to do that without also fixing how port and branch device refcounting works so that it actually makes sense, since the current upstream implementation requires a

This is the series I've been working on for a while now to get all of the atomic DRM drivers in the tree to use the atomic MST helpers, and to make the atomic MST helpers actually idempotent. Turns out it's a lot more difficult to do that without also fixing how port and branch device refcounting works so that it actually makes sense, since the current upstream implementation requires a

...ad(&port->malloc_kref) - 1); > + DRM_DEBUG("port %p/%px (%d)\n", > + port, port, kref_read(&port->malloc_kref) - 1); > kref_put(&port->malloc_kref, drm_dp_free_mst_port); > } > EXPORT_SYMBOL(drm_dp_mst_put_port_malloc); > @@ -1447,8 +1451,8 @@ drm_dp_mst_topology_try_get_mstb(struct drm_dp_mst_branch *mstb) > int ret = kref_get_unless_zero(&mstb->topology_kref); > > if (ret) > - DRM_DEBUG("mstb %p (%d)\n", mstb, > - kref_read(&mstb->topology_kref)); > + DRM_DEBUG("mstb %p/%px (%d)\n", > + mstb, mstb,...

This is the series I've been working on for a while now to get all of the atomic DRM drivers in the tree to use the atomic MST helpers, and to make the atomic MST helpers actually idempotent. Turns out it's a lot more difficult to do that without also fixing how port and branch device refcounting works so that it actually makes sense, since the current upstream implementation requires a

This is the series I've been working on for a while now to get all of the atomic DRM drivers in the tree to use the atomic MST helpers, and to make the atomic MST helpers actually idempotent. Turns out it's a lot more difficult to do that without also fixing how port and branch device refcounting works so that it actually makes sense, since the current upstream implementation requires a

...mst_branch, topology_kref); struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; + drm_dp_mst_dump_mstb_topology_history(mstb); + INIT_LIST_HEAD(&mstb->destroy_next); /* @@ -1448,11 +1632,18 @@ static void drm_dp_destroy_mst_branch_device(struct kref *kref) static int __must_check drm_dp_mst_topology_try_get_mstb(struct drm_dp_mst_branch *mstb) { - int ret = kref_get_unless_zero(&mstb->topology_kref); + int ret; - if (ret) + topology_ref_history_lock(mstb->mgr); + ret = kref_get_unless_zero(&mstb->topology_kref); + + if (ret) { DRM_DEBUG("mstb %p/%px (%d)\n", mstb, mst...

This is the series I've been working on for a while now to get all of the atomic DRM drivers in the tree to use the atomic MST helpers, and to make the atomic MST helpers actually idempotent. Turns out it's a lot more difficult to do that without also fixing how port and branch device refcounting works so that it actually makes sense, since the current upstream implementation requires a

This is the series I've been working on for a while now to get all of the atomic DRM drivers in the tree to use the atomic MST helpers, and to make the atomic MST helpers actually idempotent. Turns out it's a lot more difficult to do that without also fixing how port and branch device refcounting works so that it actually makes sense, since the current upstream implementation requires a

...mst_branch, topology_kref); struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; + drm_dp_mst_dump_mstb_topology_history(mstb); + INIT_LIST_HEAD(&mstb->destroy_next); /* @@ -1442,11 +1624,17 @@ static void drm_dp_destroy_mst_branch_device(struct kref *kref) static int __must_check drm_dp_mst_topology_try_get_mstb(struct drm_dp_mst_branch *mstb) { - int ret = kref_get_unless_zero(&mstb->topology_kref); + int ret; - if (ret) - DRM_DEBUG("mstb %p (%d)\n", mstb, - kref_read(&mstb->topology_kref)); + topology_ref_history_lock(mstb->mgr); + ret = kref_get_unless_zero(&mstb-&...

...%p (%d)\n", port, kref_read(&port->malloc_kref) - 1); + DRM_DEBUG("port %p/%px (%d)\n", + port, port, kref_read(&port->malloc_kref) - 1); kref_put(&port->malloc_kref, drm_dp_free_mst_port); } EXPORT_SYMBOL(drm_dp_mst_put_port_malloc); @@ -1447,8 +1451,8 @@ drm_dp_mst_topology_try_get_mstb(struct drm_dp_mst_branch *mstb) int ret = kref_get_unless_zero(&mstb->topology_kref); if (ret) - DRM_DEBUG("mstb %p (%d)\n", mstb, - kref_read(&mstb->topology_kref)); + DRM_DEBUG("mstb %p/%px (%d)\n", + mstb, mstb, kref_read(&mstb->topology_k...

...ng? > > > Good question! There's only one instance where we unconditionally grab an MSTB > ref, drm_dp_mst_topology_mgr_set_mst(), and in that location we're guaranteed > to be the only one with access to that mstb until we drop &mgr->lock. > Everywhere else we use drm_dp_mst_topology_try_get_mstb(), which uses > kref_get_unless_zero() to protect against that kind of situation (and forces > the caller to check with __must_check) Awesome, thanks for the breakdown! Reviewed-by: Sean Paul <sean at poorly.run> > > > Sean > > > > > --- > > > dr...

...ayed destroy worker running? > Good question! There's only one instance where we unconditionally grab an MSTB ref, drm_dp_mst_topology_mgr_set_mst(), and in that location we're guaranteed to be the only one with access to that mstb until we drop &mgr->lock. Everywhere else we use drm_dp_mst_topology_try_get_mstb(), which uses kref_get_unless_zero() to protect against that kind of situation (and forces the caller to check with __must_check) > Sean > > > --- > > drivers/gpu/drm/drm_dp_mst_topology.c | 162 +++++++++++++++++--------- > > include/drm/drm_dp_mst_helper.h | 26 +...

On Tue, Sep 03, 2019 at 04:45:41PM -0400, Lyude Paul wrote: > When reprobing an MST topology during resume, we have to account for the > fact that while we were suspended it's possible that mstbs may have been > removed from any ports in the topology. Since iterating downwards in the > topology requires that we hold &mgr->lock, destroying MSTBs from this > context would

This is the large series for adding MST suspend/resume reprobing that I've been working on for quite a while now. In addition, I: - Refactored and cleaned up any code I ended up digging through in the process of understanding how some parts of these helpers worked. - Added some debugging tools along the way that I ended up needing to figure out some issues in my own code Note that

This is the final portion of the large series for adding MST suspend/resume reprobing that I've been working on for quite a while now. In addition, I: * Refactored and cleaned up any code I ended up digging through in the process of understanding how some parts of these helpers worked. * Added some debugging tools along the way that I ended up needing to figure out some issues in my own