On Thu, 28 Sep 2023, Ramya SR <rsr@xxxxxxxxxxxxxxxx> wrote: > Reminder. Please review the reply comment. Maybe send a patch to review? It's also not helping that your previous mail looks like it's just quoting other messages [1]. BR, Jani. [1] https://lore.kernel.org/all/BN0PR02MB79517B267D593DC484BA34DF81C3A@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > > Thanks and Regards, > Ramya SR > > -----Original Message----- > From: Ramya SR > Sent: Tuesday, September 26, 2023 4:12 PM > To: Alex Deucher <alexdeucher@xxxxxxxxx>; imre.deak@xxxxxxxxx > Cc: Lyude Paul <lyude@xxxxxxxxxx>; Jani Nikula <jani.nikula@xxxxxxxxx>; Jeff Layton <jlayton@xxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; Wayne Lin <Wayne.Lin@xxxxxxx>; Alex Deucher <alexander.deucher@xxxxxxx>; Ramya SR (QUIC) <quic_rsr@xxxxxxxxxxx> > Subject: RE: [PATCH v1] drm/dp/mst: fix missing modeset unlock for MST port detect > > > > -----Original Message----- > From: Alex Deucher <alexdeucher@xxxxxxxxx> > Sent: Monday, September 25, 2023 8:27 PM > To: imre.deak@xxxxxxxxx > Cc: Lyude Paul <lyude@xxxxxxxxxx>; Jani Nikula <jani.nikula@xxxxxxxxx>; Jeff Layton <jlayton@xxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; Wayne Lin <Wayne.Lin@xxxxxxx>; Alex Deucher <alexander.deucher@xxxxxxx>; Ramya SR (QUIC) <quic_rsr@xxxxxxxxxxx> > Subject: Re: [PATCH v1] drm/dp/mst: fix missing modeset unlock for MST port detect > > WARNING: This email originated from outside of Qualcomm. Please be wary of any links or attachments, and do not enable macros. > > On Fri, Sep 22, 2023 at 3:22 PM Imre Deak <imre.deak@xxxxxxxxx> wrote: >> >> On Fri, Sep 22, 2023 at 03:02:23PM -0400, Lyude Paul wrote: >> > >> > Oh! wow thank you for catching this: >> > >> > Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx> >> > >> > I will go and push this to drm-misc-next in just a moment >> > >> > On Fri, 2023-09-15 at 10:24 +0530, Ramya SR wrote: >> > > Modeset mutex unlock is missing in drm_dp_mst_detect_port function. >> > > This will lead to deadlock if calling the function multiple times >> > > in an atomic operation, for example, getting imultiple MST ports >> > > status for a DP MST bonding scenario. >> > > >> > > Signed-off-by: Ramya SR <quic_rsr@xxxxxxxxxxx> >> > > --- >> > > drivers/gpu/drm/display/drm_dp_mst_topology.c | 4 +++- >> > > 1 file changed, 3 insertions(+), 1 deletion(-) >> > > >> > > diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c >> > > b/drivers/gpu/drm/display/drm_dp_mst_topology.c >> > > index ed96cfc..d6512c4 100644 >> > > --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c >> > > +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c >> > > @@ -4154,7 +4154,7 @@ drm_dp_mst_detect_port(struct drm_connector >> > > *connector, >> > > >> > > ret = drm_modeset_lock(&mgr->base.lock, ctx); >> > > if (ret) >> > > - goto out; >> > > + goto fail; >> > > >> > > ret = connector_status_disconnected; >> > > >> > > @@ -4181,6 +4181,8 @@ drm_dp_mst_detect_port(struct drm_connector *connector, >> > > break; >> > > } >> > > out: >> > > + drm_modeset_unlock(&mgr->base.lock); >> >> Isn't this supposed to be unlocked only by >> drm_helper_probe_detect_ctx() / drm_helper_probe_detect() ? > > Maybe adding a comment to that effect would be helpful for the future. > > Alex > >>this is different lock, above function mentioned is locking/unlocking the global connection_mutex, that is required always locked during the atomic >check/commit. Here we are talking about MST topology manager mutex "mgr->base.lock". > >>For normal non-bond MST, it's ok, the calling sequence for detecting >>MST connector status is dp_mst_connector_detect >>->mst->mst_fw_cbs->detect_port_ctx = dp_mst_detect_port >>->drm_dp_mst_detect_port (where mgr->base.lock is locked) > >> Then for the bond MST case, to figure out if the sibling connectors >> are also connected, so that the bonding is possible, we need detect >> two or more connectors >in single dp_mst_connector_detect call > >>dp_mst_connector_detect ->mst->mst_fw_cbs->detect_port_ctx = >>dp_mst_detect_port ->drm_dp_mst_detect_port (where mgr->base.lock is >>locked) dp_mst_find_sibling_connector >>->mst->mst_fw_cbs->detect_port_ctx = dp_mst_detect_port >>->drm_dp_mst_detect_port (blocked by mgr->base.lock) > >> >> > > +fail: >> > > drm_dp_mst_topology_put_port(port); >> > > return ret; >> > > } >> > >> > -- >> > Cheers, >> > Lyude Paul (she/her) >> > Software Engineer at Red Hat >> > -- Jani Nikula, Intel
