RE: [PATCH 5.0 072/246] drm/amd/display: Fix reference counting for struct dc_sink.

["Deucher, Alexander" <Alexander.Deucher@amd.com>]

> -----Original Message-----
> From: Mathias Fröhlich <Mathias.Froehlich@gmx.net>
> Sent: Friday, April 5, 2019 1:13 AM
> To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: linux-kernel@vger.kernel.org; stable@vger.kernel.org; Li, Sun peng (Leo)
> <Sunpeng.Li@amd.com>; Deucher, Alexander
> <Alexander.Deucher@amd.com>; Sasha Levin <sashal@kernel.org>
> Subject: Re: [PATCH 5.0 072/246] drm/amd/display: Fix reference counting
> for struct dc_sink.
> 
> Greg,
> 
> as I mentioned in the commit message, I saw more fixes to that area in Alex
> Deuchers queue when I fed that to Alex. There is one fix that I can think of
> that interacts with my fixes. Means, we may get unwanted side effects of my
> patch without the fix mentioned below. With that below patch also selected,
> I think we should be ok for stable.
> Alex, AMD people, your opinion?

I'm not sure.  I haven't gone through to figure out what combinations of all of these patches are required for each stable kernel.  The combinatorics are too much which is why I only cc stable on certain patches.  Harry or Leo may have be able to comment however.

Alex

> 
> The one that I can spot not already in linux-5.0.y is:
> 
> commit 3f01f098a4e2ef30ef628497c43a3d568e720376
> Author: Jerry (Fangzhi) Zuo <Jerry.Zuo@amd.com>
> Date:   Thu Jan 24 11:46:49 2019 -0500
> 
>     drm/amd/display: Clear dc_sink after it gets released
> 
>     [Why]
>     The dc_sink was released but the pointer on the aconnector was
>     not cleared.
> 
>     [How]
>     Clear it.
> 
> best
> 
> Mathias
> 
> 
> On Thursday, 4 April 2019 10:46:12 CEST Greg Kroah-Hartman wrote:
> > 5.0-stable review patch.  If anyone has any objections, please let me know.
> >
> > ------------------
> >
> > [ Upstream commit dcd5fb82ffb484124203aa339733663ac0b059f3 ]
> >
> > Reference counting in amdgpu_dm_connector for
> > amdgpu_dm_connector::dc_sink and
> amdgpu_dm_connector::dc_em_sink as
> > well as in dc_link::local_sink seems to be out of shape. Thus make
> > reference counting consistent for these members and just plain
> > increment the reference count when the variable gets assigned and
> decrement when the pointer is set to zero or replaced.
> > Also simplify reference counting in selected function sopes to be sure
> > the reference is released in any case. In some cases add NULL pointer
> > check before dereferencing.
> > At a hand full of places a comment is placed to stat that the
> > reference increment happened already somewhere else.
> >
> > This actually fixes the following kernel bug on my system when
> > enabling display core in amdgpu. There are some more similar bug
> > reports around, so it probably helps at more places.
> >
> >    kernel BUG at mm/slub.c:294!
> >    invalid opcode: 0000 [#1] SMP PTI
> >    CPU: 9 PID: 1180 Comm: Xorg Not tainted 5.0.0-rc1+ #2
> >    Hardware name: Supermicro X10DAi/X10DAI, BIOS 3.0a 02/05/2018
> >    RIP: 0010:__slab_free+0x1e2/0x3d0
> >    Code: 8b 54 24 30 48 89 4c 24 28 e8 da fb ff ff 4c 8b 54 24 28 85 c0 0f 85 67 fe
> ff ff 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 <0f> 0b 49 3b 5c 24 28 75 ab 48
> 8b 44 24 30 49 89 4c 24 28 49 89 44
> >    RSP: 0018:ffffb0978589fa90 EFLAGS: 00010246
> >    RAX: ffff92f12806c400 RBX: 0000000080200019 RCX: ffff92f12806c400
> >    RDX: ffff92f12806c400 RSI: ffffdd6421a01a00 RDI: ffff92ed2f406e80
> >    RBP: ffffb0978589fb40 R08: 0000000000000001 R09: ffffffffc0ee4748
> >    R10: ffff92f12806c400 R11: 0000000000000001 R12: ffffdd6421a01a00
> >    R13: ffff92f12806c400 R14: ffff92ed2f406e80 R15: ffffdd6421a01a20
> >    FS:  00007f4170be0ac0(0000) GS:ffff92ed2fb40000(0000)
> knlGS:0000000000000000
> >    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >    CR2: 0000562818aaa000 CR3: 000000045745a002 CR4: 00000000003606e0
> >    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >    Call Trace:
> >     ? drm_dbg+0x87/0x90 [drm]
> >     dc_stream_release+0x28/0x50 [amdgpu]
> >     amdgpu_dm_connector_mode_valid+0xb4/0x1f0 [amdgpu]
> >     drm_helper_probe_single_connector_modes+0x492/0x6b0
> [drm_kms_helper]
> >     drm_mode_getconnector+0x457/0x490 [drm]
> >     ? drm_connector_property_set_ioctl+0x60/0x60 [drm]
> >     drm_ioctl_kernel+0xa9/0xf0 [drm]
> >     drm_ioctl+0x201/0x3a0 [drm]
> >     ? drm_connector_property_set_ioctl+0x60/0x60 [drm]
> >     amdgpu_drm_ioctl+0x49/0x80 [amdgpu]
> >     do_vfs_ioctl+0xa4/0x630
> >     ? __sys_recvmsg+0x83/0xa0
> >     ksys_ioctl+0x60/0x90
> >     __x64_sys_ioctl+0x16/0x20
> >     do_syscall_64+0x5b/0x160
> >     entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >    RIP: 0033:0x7f417110809b
> >    Code: 0f 1e fa 48 8b 05 ed bd 0c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3
> 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b
> 0d bd bd 0c 00 f7 d8 64 89 01 48
> >    RSP: 002b:00007ffdd8d1c268 EFLAGS: 00000246 ORIG_RAX:
> 0000000000000010
> >    RAX: ffffffffffffffda RBX: 0000562818a8ebc0 RCX: 00007f417110809b
> >    RDX: 00007ffdd8d1c2a0 RSI: 00000000c05064a7 RDI: 0000000000000012
> >    RBP: 00007ffdd8d1c2a0 R08: 0000562819012280 R09: 0000000000000007
> >    R10: 0000000000000000 R11: 0000000000000246 R12: 00000000c05064a7
> >    R13: 0000000000000012 R14: 0000000000000012 R15: 00007ffdd8d1c2a0
> >    Modules linked in: nfsv4 dns_resolver nfs lockd grace fscache fuse
> > vfat fat amdgpu intel_rapl sb_edac x86_pkg_temp_thermal
> > intel_powerclamp coretemp kvm_intel kvm irqbypass crct10dif_pclmul
> > chash gpu_sched crc32_pclmul snd_hda_codec_realtek
> ghash_clmulni_intel
> > amd_iommu_v2 iTCO_wdt iTCO_vendor_support ttm
> snd_hda_codec_generic
> > snd_hda_codec_hdmi ledtrig_audio snd_hda_intel drm_kms_helper
> > snd_hda_codec intel_cstate snd_hda_core drm snd_hwdep snd_seq
> > snd_seq_device intel_uncore snd_pcm intel_rapl_perf snd_timer snd
> > soundcore ioatdma pcspkr intel_wmi_thunderbolt mxm_wmi i2c_i801
> > lpc_ich pcc_cpufreq auth_rpcgss sunrpc igb crc32c_intel i2c_algo_bit
> > dca wmi hid_cherry analog gameport joydev
> >
> > This patch is based on agd5f/drm-next-5.1-wip. This patch does not
> > require all of that, but agd5f/drm-next-5.1-wip contains at least one
> > more dc_sink counting fix that I could spot.
> >
> > Signed-off-by: Mathias Fröhlich <Mathias.Froehlich@web.de>
> > Reviewed-by: Leo Li <sunpeng.li@amd.com>
> > Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
> > Signed-off-by: Sasha Levin <sashal@kernel.org>
> > ---
> >  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 43
> +++++++++++++++----
> >  .../display/amdgpu_dm/amdgpu_dm_mst_types.c   |  1 +
> >  drivers/gpu/drm/amd/display/dc/core/dc_link.c |  1 +
> >  3 files changed, 37 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > index 636d14a60952..6d77fd966dbd 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > @@ -886,6 +886,7 @@ static void emulated_link_detect(struct dc_link
> *link)
> >  		return;
> >  	}
> >
> > +	/* dc_sink_create returns a new reference */
> >  	link->local_sink = sink;
> >
> >  	edid_status = dm_helpers_read_local_edid( @@ -952,6 +953,8 @@
> static
> > int dm_resume(void *handle)
> >  		if (aconnector->fake_enable && aconnector->dc_link-
> >local_sink)
> >  			aconnector->fake_enable = false;
> >
> > +		if (aconnector->dc_sink)
> > +			dc_sink_release(aconnector->dc_sink);
> >  		aconnector->dc_sink = NULL;
> >  		amdgpu_dm_update_connector_after_detect(aconnector);
> >  		mutex_unlock(&aconnector->hpd_lock);
> > @@ -1061,6 +1064,8 @@
> amdgpu_dm_update_connector_after_detect(struct
> > amdgpu_dm_connector *aconnector)
> >
> >
> >  	sink = aconnector->dc_link->local_sink;
> > +	if (sink)
> > +		dc_sink_retain(sink);
> >
> >  	/*
> >  	 * Edid mgmt connector gets first update only in mode_valid hook
> and
> > then @@ -1085,21 +1090,24 @@
> amdgpu_dm_update_connector_after_detect(struct
> amdgpu_dm_connector *aconnector)
> >  				 * to it anymore after disconnect, so on next
> crtc to connector
> >  				 * reshuffle by UMD we will get into
> unwanted dc_sink release
> >  				 */
> > -				if (aconnector->dc_sink != aconnector-
> >dc_em_sink)
> > -					dc_sink_release(aconnector-
> >dc_sink);
> > +				dc_sink_release(aconnector->dc_sink);
> >  			}
> >  			aconnector->dc_sink = sink;
> > +			dc_sink_retain(aconnector->dc_sink);
> >  			amdgpu_dm_update_freesync_caps(connector,
> >  					aconnector->edid);
> >  		} else {
> >  			amdgpu_dm_update_freesync_caps(connector,
> NULL);
> > -			if (!aconnector->dc_sink)
> > +			if (!aconnector->dc_sink) {
> >  				aconnector->dc_sink = aconnector-
> >dc_em_sink;
> > -			else if (aconnector->dc_sink != aconnector-
> >dc_em_sink)
> >  				dc_sink_retain(aconnector->dc_sink);
> > +			}
> >  		}
> >
> >  		mutex_unlock(&dev->mode_config.mutex);
> > +
> > +		if (sink)
> > +			dc_sink_release(sink);
> >  		return;
> >  	}
> >
> > @@ -1107,8 +1115,10 @@
> amdgpu_dm_update_connector_after_detect(struct
> amdgpu_dm_connector *aconnector)
> >  	 * TODO: temporary guard to look for proper fix
> >  	 * if this sink is MST sink, we should not do anything
> >  	 */
> > -	if (sink && sink->sink_signal == SIGNAL_TYPE_DISPLAY_PORT_MST)
> > +	if (sink && sink->sink_signal == SIGNAL_TYPE_DISPLAY_PORT_MST) {
> > +		dc_sink_release(sink);
> >  		return;
> > +	}
> >
> >  	if (aconnector->dc_sink == sink) {
> >  		/*
> > @@ -1117,6 +1127,8 @@
> amdgpu_dm_update_connector_after_detect(struct
> amdgpu_dm_connector *aconnector)
> >  		 */
> >  		DRM_DEBUG_DRIVER("DCHPD: connector_id=%d: dc_sink
> didn't change.\n",
> >  				aconnector->connector_id);
> > +		if (sink)
> > +			dc_sink_release(sink);
> >  		return;
> >  	}
> >
> > @@ -1138,6 +1150,7 @@
> amdgpu_dm_update_connector_after_detect(struct
> amdgpu_dm_connector *aconnector)
> >  			amdgpu_dm_update_freesync_caps(connector,
> NULL);
> >
> >  		aconnector->dc_sink = sink;
> > +		dc_sink_retain(aconnector->dc_sink);
> >  		if (sink->dc_edid.length == 0) {
> >  			aconnector->edid = NULL;
> >  			drm_dp_cec_unset_edid(&aconnector-
> >dm_dp_aux.aux);
> > @@ -1158,11 +1171,15 @@
> amdgpu_dm_update_connector_after_detect(struct
> amdgpu_dm_connector *aconnector)
> >  		amdgpu_dm_update_freesync_caps(connector, NULL);
> >  		drm_connector_update_edid_property(connector, NULL);
> >  		aconnector->num_modes = 0;
> > +		dc_sink_release(aconnector->dc_sink);
> >  		aconnector->dc_sink = NULL;
> >  		aconnector->edid = NULL;
> >  	}
> >
> >  	mutex_unlock(&dev->mode_config.mutex);
> > +
> > +	if (sink)
> > +		dc_sink_release(sink);
> >  }
> >
> >  static void handle_hpd_irq(void *param) @@ -2908,6 +2925,7 @@
> > create_stream_for_sink(struct amdgpu_dm_connector *aconnector,
> >  		}
> >  	} else {
> >  		sink = aconnector->dc_sink;
> > +		dc_sink_retain(sink);
> >  	}
> >
> >  	stream = dc_create_stream_for_sink(sink); @@ -2974,8 +2992,7 @@
> > create_stream_for_sink(struct amdgpu_dm_connector *aconnector,
> >  		stream->ignore_msa_timing_param = true;
> >
> >  finish:
> > -	if (sink && sink->sink_signal == SIGNAL_TYPE_VIRTUAL &&
> aconnector->base.force != DRM_FORCE_ON)
> > -		dc_sink_release(sink);
> > +	dc_sink_release(sink);
> >
> >  	return stream;
> >  }
> > @@ -3233,6 +3250,14 @@ static void
> amdgpu_dm_connector_destroy(struct drm_connector *connector)
> >  		dm->backlight_dev = NULL;
> >  	}
> >  #endif
> > +
> > +	if (aconnector->dc_em_sink)
> > +		dc_sink_release(aconnector->dc_em_sink);
> > +	aconnector->dc_em_sink = NULL;
> > +	if (aconnector->dc_sink)
> > +		dc_sink_release(aconnector->dc_sink);
> > +	aconnector->dc_sink = NULL;
> > +
> >  	drm_dp_cec_unregister_connector(&aconnector-
> >dm_dp_aux.aux);
> >  	drm_connector_unregister(connector);
> >  	drm_connector_cleanup(connector);
> > @@ -3330,10 +3355,12 @@ static void create_eml_sink(struct
> amdgpu_dm_connector *aconnector)
> >  		(edid->extensions + 1) * EDID_LENGTH,
> >  		&init_params);
> >
> > -	if (aconnector->base.force == DRM_FORCE_ON)
> > +	if (aconnector->base.force == DRM_FORCE_ON) {
> >  		aconnector->dc_sink = aconnector->dc_link->local_sink ?
> >  		aconnector->dc_link->local_sink :
> >  		aconnector->dc_em_sink;
> > +		dc_sink_retain(aconnector->dc_sink);
> > +	}
> >  }
> >
> >  static void handle_edid_mgmt(struct amdgpu_dm_connector
> *aconnector)
> > diff --git
> > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > index 1b0d209d8367..3b95a637b508 100644
> > ---
> a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > +++
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > @@ -239,6 +239,7 @@ static int dm_dp_mst_get_modes(struct
> drm_connector *connector)
> >  			&init_params);
> >
> >  		dc_sink->priv = aconnector;
> > +		/* dc_link_add_remote_sink returns a new reference */
> >  		aconnector->dc_sink = dc_sink;
> >
> >  		if (aconnector->dc_sink)
> > diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> > b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> > index b0265dbebd4c..583eb367850f 100644
> > --- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> > +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> > @@ -792,6 +792,7 @@ bool dc_link_detect(struct dc_link *link, enum
> dc_detect_reason reason)
> >  		sink->dongle_max_pix_clk =
> sink_caps.max_hdmi_pixel_clock;
> >  		sink->converter_disable_audio = converter_disable_audio;
> >
> > +		/* dc_sink_create returns a new reference */
> >  		link->local_sink = sink;
> >
> >  		edid_status = dm_helpers_read_local_edid(
> >
> 
> 
>