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

From: Mathias Fröhlich
Date: Fri Apr 05 2019 - 01:13:30 EST

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?

The one that I can spot not already in linux-5.0.y is:

commit 3f01f098a4e2ef30ef628497c43a3d568e720376
Author: Jerry (Fangzhi) Zuo <Jerry.Zuo@xxxxxxx>
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@xxxxxx>
> Reviewed-by: Leo Li <sunpeng.li@xxxxxxx>
> Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> ---
> .../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(
>