From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesse Barnes Subject: Re: [PATCH] drm: Hold the mode mutex whilst probing for sysfs status Date: Tue, 15 Mar 2011 08:35:39 -0700 Message-ID: <20110315083539.69edc4de@jbarnes-desktop> References: <1300181753.3759.72.camel@mattotaupa> <1300189200-9069-1-git-send-email-chris@chris-wilson.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1300189200-9069-1-git-send-email-chris@chris-wilson.co.uk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: stable-bounces@linux.kernel.org Errors-To: stable-bounces@linux.kernel.org To: Chris Wilson Cc: Dave Airlie , intel-gfx@lists.freedesktop.org, stable@kernel.org, dri-devel@lists.freedesktop.org, Paul Menzel List-Id: dri-devel@lists.freedesktop.org On Tue, 15 Mar 2011 11:40:00 +0000 Chris Wilson wrote: > As detect will use hw registers and may modify structures, it needs to be > serialised by use of the dev->mode_config.mutex. Make it so. > > Otherwise, we may cause random crashes as the sysfs file is queried > whilst a concurrent hotplug poll is being run. For example: > > [ 1189.189626] BUG: unable to handle kernel NULL pointer dereference at 00000100 > [ 1189.189821] IP: [] intel_tv_detect_type+0xa2/0x203 [i915] > [ 1189.190020] *pde = 00000000 > [ 1189.190104] Oops: 0000 [#1] SMP > [ 1189.190209] last sysfs file: /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-SVIDEO-1/status > [ 1189.190412] Modules linked in: mperf cpufreq_conservative cpufreq_userspace cpufreq_powersave cpufreq_stats decnet uinput fuse loop joydev snd_hd a_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep snd_pcm_oss snd_mixer_oss snd_pcm i915 snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq drm_kms_helper snd_timer uvcvideo d rm snd_seq_device eeepc_laptop tpm_tis usbhid videodev i2c_algo_bit v4l1_compat snd sparse_keymap i2c_core hid serio_raw tpm psmouse evdev tpm_bios rfkill shpchp ac processor rng_c ore battery video power_supply soundcore pci_hotplug button output snd_page_alloc usb_storage uas ext3 jbd mbcache sd_mod crc_t10dif ata_generic ahci libahci ata_piix libata uhci_h cd ehci_hcd scsi_mod usbcore thermal atl2 thermal_sys nls_base [last unloaded: scsi_wait_scan] > [ 1189.192007] > [ 1189.192007] Pid: 1464, comm: upowerd Not tainted 2.6.37-2-686 #1 ASUSTeK Computer INC. 701/701 > [ 1189.192007] EIP: 0060:[] EFLAGS: 00010246 CPU: 0 > [ 1189.192007] EIP is at intel_tv_detect_type+0xa2/0x203 [i915] > [ 1189.192007] EAX: 00000000 EBX: dca74000 ECX: e0f68004 EDX: 00068004 > [ 1189.192007] ESI: dd110c00 EDI: 400c0c37 EBP: dca7429c ESP: de365e2c > [ 1189.192007] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 > [ 1189.192007] Process upowerd (pid: 1464, ti=de364000 task=dcc8acb0 task.ti=de364000) > [ 1189.192007] Stack: Mar 15 03:43:23 hostname kernel: [ 1189.192007] e0c2cda4 70000000 400c0c30 00000000 dd111000 de365e54 de365f24 dd110c00 > [ 1189.192007] e0c22203 01000000 00000003 00000000 00000000 00000000 00000000 4353544e > [ 1189.192007] 30383420 00000069 00000000 00000000 00000000 00000000 00000000 00000000 > [ 1189.192007] Call Trace: Mar 15 03:43:23 hostname kernel: [ 1189.192007] [] ? intel_tv_detect+0x89/0x12d [i915] > [ 1189.192007] [] ? status_show+0x0/0x2f [drm] > [ 1189.192007] [] ? status_show+0x14/0x2f [drm] > > [Digression: what is upowerd doing reading those power hungry files?] > > Reported-by: Paul Menzel > Signed-off-by: Chris Wilson > Cc: stable@kernel.org > --- > drivers/gpu/drm/drm_sysfs.c | 7 +++++++ > 1 files changed, 7 insertions(+), 0 deletions(-) > > diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c > index 85da4c4..2eee8e0 100644 > --- a/drivers/gpu/drm/drm_sysfs.c > +++ b/drivers/gpu/drm/drm_sysfs.c > @@ -158,8 +158,15 @@ static ssize_t status_show(struct device *device, > { > struct drm_connector *connector = to_drm_connector(device); > enum drm_connector_status status; > + int ret; > + > + ret = mutex_lock_interruptible(&connector->dev->mode_config.mutex); > + if (ret) > + return ret; > > status = connector->funcs->detect(connector, true); > + mutex_unlock(&connector->dev->mode_config.mutex); > + How about adding a mutex assertion check in the detect hook as well? I think we need a more generous sprinkling of those around the CRTC helper code in general... -- Jesse Barnes, Intel Open Source Technology Center