[Intel-gfx] [PATCH v4 1/1] drm/fb-helper: Avoid race with DRM userspace
Noralf Trønnes
noralf at tronnes.org
Sun May 5 09:16:54 UTC 2019
Den 04.05.2019 14.34, skrev Noralf Trønnes:
>
>
> Den 25.04.2019 10.31, skrev Noralf Trønnes:
>> drm_fb_helper_is_bound() is used to check if DRM userspace is in control.
>> This is done by looking at the fb on the primary plane. By the time
>> fb-helper gets around to committing, it's possible that the facts have
>> changed.
>>
>> Avoid this race by holding the drm_device->master_mutex lock while
>> committing. When DRM userspace does its first open, it will now wait
>> until fb-helper is done. The helper will stay away if there's a master.
>>
>> Locking rule: Always take the fb-helper lock first.
>>
>> v2:
>> - Remove drm_fb_helper_is_bound() (Daniel Vetter)
>> - No need to check fb_helper->dev->master in
>> drm_fb_helper_single_fb_probe(), restore_fbdev_mode() has the check.
>>
>> Suggested-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>> Signed-off-by: Noralf Trønnes <noralf at tronnes.org>
>> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>> ---
>> drivers/gpu/drm/drm_auth.c | 20 ++++++++
>> drivers/gpu/drm/drm_fb_helper.c | 90 ++++++++++++++++-----------------
>> drivers/gpu/drm/drm_internal.h | 2 +
>> 3 files changed, 67 insertions(+), 45 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c
>> index 1669c42c40ed..db199807b7dc 100644
>> --- a/drivers/gpu/drm/drm_auth.c
>> +++ b/drivers/gpu/drm/drm_auth.c
>> @@ -368,3 +368,23 @@ void drm_master_put(struct drm_master **master)
>> *master = NULL;
>> }
>> EXPORT_SYMBOL(drm_master_put);
>> +
>> +/* Used by drm_client and drm_fb_helper */
>> +bool drm_master_internal_acquire(struct drm_device *dev)
>> +{
>> + mutex_lock(&dev->master_mutex);
>> + if (dev->master) {
>> + mutex_unlock(&dev->master_mutex);
>> + return false;
>> + }
>> +
>> + return true;
>> +}
>> +EXPORT_SYMBOL(drm_master_internal_acquire);
>> +
>> +/* Used by drm_client and drm_fb_helper */
>> +void drm_master_internal_release(struct drm_device *dev)
>> +{
>> + mutex_unlock(&dev->master_mutex);
>> +}
>> +EXPORT_SYMBOL(drm_master_internal_release);
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
>> index 2339f0f8f5a8..578428461391 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -44,6 +44,7 @@
>>
>> #include "drm_crtc_internal.h"
>> #include "drm_crtc_helper_internal.h"
>> +#include "drm_internal.h"
>>
>> static bool drm_fbdev_emulation = true;
>> module_param_named(fbdev_emulation, drm_fbdev_emulation, bool, 0600);
>> @@ -509,7 +510,7 @@ static int restore_fbdev_mode_legacy(struct drm_fb_helper *fb_helper)
>> return ret;
>> }
>>
>> -static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
>> +static int restore_fbdev_mode_force(struct drm_fb_helper *fb_helper)
>> {
>> struct drm_device *dev = fb_helper->dev;
>>
>> @@ -519,6 +520,21 @@ static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
>> return restore_fbdev_mode_legacy(fb_helper);
>> }
>>
>> +static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
>> +{
>> + struct drm_device *dev = fb_helper->dev;
>> + int ret;
>> +
>> + if (!drm_master_internal_acquire(dev))
>> + return -EBUSY;
>> +
>> + ret = restore_fbdev_mode_force(fb_helper);
>> +
>> + drm_master_internal_release(dev);
>> +
>> + return ret;
>> +}
>> +
>> /**
>> * drm_fb_helper_restore_fbdev_mode_unlocked - restore fbdev configuration
>> * @fb_helper: driver-allocated fbdev helper, can be NULL
>
> The Intel CI doesn't like this patch. AFAICT the reason is that the
> igt at kms_fbcon_fbt@psr-suspend test expects fbcon to work while it has an
> open fd that is master. This doesn't match the new rule of bailing out
> if there's a master.
>
> Adding this debug output:
>
> @@ -558,6 +558,17 @@ int
> drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
> return 0;
>
> mutex_lock(&fb_helper->lock);
> +if (READ_ONCE(fb_helper->dev->master)) {
> + int level = default_message_loglevel;
> +
> + default_message_loglevel = LOGLEVEL_DEBUG;
> + printk("\n");
> + printk("\n");
> + printk("%s\n", __func__);
> + printk(" THERE IS A MASTER\n");
> + dump_stack();
> + default_message_loglevel = level;
> +}
> ret = restore_fbdev_mode_force(fb_helper);
>
> do_delayed = fb_helper->delayed_hotplug;
>
> Gives these log entries:
>
> <7> [1857.940072] drm_fb_helper_restore_fbdev_mode_unlocked
> <7> [1857.940074] THERE IS A MASTER
> <7> [1857.940079] CPU: 4 PID: 8209 Comm: kms_fbcon_fbt Tainted: G U
> 5.1.0-rc7-CI-Trybot_4252+ #1
> <7> [1857.940081] Hardware name: Intel Corporation Ice Lake Client
> Platform/IceLake U DDR4 SODIMM PD RVP, BIOS
> ICLSFWR1.R00.3121.A00.1903190527 03/19/2019
> <7> [1857.940083] Call Trace:
> <7> [1857.940091] dump_stack+0x67/0x9b
> <7> [1857.940099] drm_fb_helper_restore_fbdev_mode_unlocked+0xda/0xf0
> <7> [1857.940104] drm_fb_helper_set_par+0x24/0x50
> <7> [1857.940188] intel_fbdev_set_par+0x11/0x40 [i915]
> <7> [1857.940197] fb_set_var+0x17a/0x3f0
> <7> [1857.940212] ? __lock_acquire+0x49f/0x1590
> <7> [1857.940230] fbcon_blank+0x192/0x2e0
> <7> [1857.940235] ? __lock_acquire+0x49f/0x1590
> <7> [1857.940254] do_unblank_screen+0xa1/0x170
> <7> [1857.940260] vt_ioctl+0x505/0x11d0
> <7> [1857.940270] tty_ioctl+0xee/0x940
> <7> [1857.940274] ? lockdep_hardirqs_off+0x94/0xd0
> <7> [1857.940278] ? __slab_free+0x24e/0x4f0
> <7> [1857.940287] ? _raw_spin_unlock_irqrestore+0x39/0x60
> <7> [1857.940291] ? kmem_cache_free+0x279/0x2e0
> <7> [1857.940299] do_vfs_ioctl+0xa0/0x6e0
> <7> [1857.940305] ? do_sys_open+0x13b/0x250
> <7> [1857.940311] ? rcu_read_lock_sched_held+0x6f/0x80
> <7> [1857.940313] ? kmem_cache_free+0x283/0x2e0
> <7> [1857.940321] ksys_ioctl+0x35/0x60
> <7> [1857.940328] __x64_sys_ioctl+0x11/0x20
> <7> [1857.940332] do_syscall_64+0x55/0x190
> <7> [1857.940337] entry_SYSCALL_64_after_hwframe+0x49/0xbe
> <7> [1857.940341] RIP: 0033:0x7faf8f0825d7
> <7> [1857.940345] Code: b3 66 90 48 8b 05 b1 48 2d 00 64 c7 00 26 00 00
> 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00
> 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 81 48 2d 00 f7 d8 64 89 01 48
> <7> [1857.940347] RSP: 002b:00007ffddf6a94b8 EFLAGS: 00000246 ORIG_RAX:
> 0000000000000010
> <7> [1857.940351] RAX: ffffffffffffffda RBX: 0000000000000000 RCX:
> 00007faf8f0825d7
> <7> [1857.940353] RDX: 0000000000000000 RSI: 0000000000004b3a RDI:
> 000000000000000a
> <7> [1857.940355] RBP: 0000000000000000 R08: 0000000000000000 R09:
> 00000000000000ab
> <7> [1857.940357] R10: 0000000000000000 R11: 0000000000000246 R12:
> 0000000000004b3a
> <7> [1857.940359] R13: 000000000000000a R14: 0000000000000000 R15:
> 0000000000000000
> <6> [1861.481078] [IGT] kms_fbcon_fbt: exiting, ret=99
>
> Patches:
> https://patchwork.freedesktop.org/series/59951/#rev8
> Failing test:
> https://intel-gfx-ci.01.org/tree/drm-tip/Trybot_4252/shard-iclb7/igt@kms_fbcon_fbt@psr-suspend.html
>
Actually there's two failing tests, this one as well:
* igt at kms_fbcon_fbt at psr:
- shard-skl: NOTRUN -> [FAIL][1]
[1]:
https://intel-gfx-ci.01.org/tree/drm-tip/Trybot_4252/shard-skl7/igt@kms_fbcon_fbt@psr.html
>
> If I make this change and don't check for master, then it's fine:
>
> @@ -542,7 +558,7 @@ int
> drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
> return 0;
>
> mutex_lock(&fb_helper->lock);
> - ret = restore_fbdev_mode(fb_helper);
> + ret = restore_fbdev_mode_force(fb_helper);
>
> do_delayed = fb_helper->delayed_hotplug;
> if (do_delayed)
>
> https://patchwork.freedesktop.org/series/59951/#rev9
>
> Should I make this change, or should the test change?
>
> Noralf.
>
>> @@ -556,34 +572,6 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
>> }
>> EXPORT_SYMBOL(drm_fb_helper_restore_fbdev_mode_unlocked);
>>
>> -static bool drm_fb_helper_is_bound(struct drm_fb_helper *fb_helper)
>> -{
>> - struct drm_device *dev = fb_helper->dev;
>> - struct drm_crtc *crtc;
>> - int bound = 0, crtcs_bound = 0;
>> -
>> - /*
>> - * Sometimes user space wants everything disabled, so don't steal the
>> - * display if there's a master.
>> - */
>> - if (READ_ONCE(dev->master))
>> - return false;
>> -
>> - drm_for_each_crtc(crtc, dev) {
>> - drm_modeset_lock(&crtc->mutex, NULL);
>> - if (crtc->primary->fb)
>> - crtcs_bound++;
>> - if (crtc->primary->fb == fb_helper->fb)
>> - bound++;
>> - drm_modeset_unlock(&crtc->mutex);
>> - }
>> -
>> - if (bound < crtcs_bound)
>> - return false;
>> -
>> - return true;
>> -}
>> -
>> #ifdef CONFIG_MAGIC_SYSRQ
>> /*
>> * restore fbcon display for all kms driver's using this helper, used for sysrq
>> @@ -604,7 +592,7 @@ static bool drm_fb_helper_force_kernel_mode(void)
>> continue;
>>
>> mutex_lock(&helper->lock);
>> - ret = restore_fbdev_mode(helper);
>> + ret = restore_fbdev_mode_force(helper);
>> if (ret)
>> error = true;
>> mutex_unlock(&helper->lock);
>> @@ -663,20 +651,22 @@ static void dpms_legacy(struct drm_fb_helper *fb_helper, int dpms_mode)
>> static void drm_fb_helper_dpms(struct fb_info *info, int dpms_mode)
>> {
>> struct drm_fb_helper *fb_helper = info->par;
>> + struct drm_device *dev = fb_helper->dev;
>>
>> /*
>> * For each CRTC in this fb, turn the connectors on/off.
>> */
>> mutex_lock(&fb_helper->lock);
>> - if (!drm_fb_helper_is_bound(fb_helper)) {
>> - mutex_unlock(&fb_helper->lock);
>> - return;
>> - }
>> + if (!drm_master_internal_acquire(dev))
>> + goto unlock;
>>
>> - if (drm_drv_uses_atomic_modeset(fb_helper->dev))
>> + if (drm_drv_uses_atomic_modeset(dev))
>> restore_fbdev_mode_atomic(fb_helper, dpms_mode == DRM_MODE_DPMS_ON);
>> else
>> dpms_legacy(fb_helper, dpms_mode);
>> +
>> + drm_master_internal_release(dev);
>> +unlock:
>> mutex_unlock(&fb_helper->lock);
>> }
>>
>> @@ -1509,6 +1499,7 @@ static int setcmap_atomic(struct fb_cmap *cmap, struct fb_info *info)
>> int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info)
>> {
>> struct drm_fb_helper *fb_helper = info->par;
>> + struct drm_device *dev = fb_helper->dev;
>> int ret;
>>
>> if (oops_in_progress)
>> @@ -1516,9 +1507,9 @@ int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info)
>>
>> mutex_lock(&fb_helper->lock);
>>
>> - if (!drm_fb_helper_is_bound(fb_helper)) {
>> + if (!drm_master_internal_acquire(dev)) {
>> ret = -EBUSY;
>> - goto out;
>> + goto unlock;
>> }
>>
>> if (info->fix.visual == FB_VISUAL_TRUECOLOR)
>> @@ -1528,7 +1519,8 @@ int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info)
>> else
>> ret = setcmap_legacy(cmap, info);
>>
>> -out:
>> + drm_master_internal_release(dev);
>> +unlock:
>> mutex_unlock(&fb_helper->lock);
>>
>> return ret;
>> @@ -1548,12 +1540,13 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
>> unsigned long arg)
>> {
>> struct drm_fb_helper *fb_helper = info->par;
>> + struct drm_device *dev = fb_helper->dev;
>> struct drm_mode_set *mode_set;
>> struct drm_crtc *crtc;
>> int ret = 0;
>>
>> mutex_lock(&fb_helper->lock);
>> - if (!drm_fb_helper_is_bound(fb_helper)) {
>> + if (!drm_master_internal_acquire(dev)) {
>> ret = -EBUSY;
>> goto unlock;
>> }
>> @@ -1591,11 +1584,12 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
>> }
>>
>> ret = 0;
>> - goto unlock;
>> + break;
>> default:
>> ret = -ENOTTY;
>> }
>>
>> + drm_master_internal_release(dev);
>> unlock:
>> mutex_unlock(&fb_helper->lock);
>> return ret;
>> @@ -1847,15 +1841,18 @@ int drm_fb_helper_pan_display(struct fb_var_screeninfo *var,
>> return -EBUSY;
>>
>> mutex_lock(&fb_helper->lock);
>> - if (!drm_fb_helper_is_bound(fb_helper)) {
>> - mutex_unlock(&fb_helper->lock);
>> - return -EBUSY;
>> + if (!drm_master_internal_acquire(dev)) {
>> + ret = -EBUSY;
>> + goto unlock;
>> }
>>
>> if (drm_drv_uses_atomic_modeset(dev))
>> ret = pan_display_atomic(var, info);
>> else
>> ret = pan_display_legacy(var, info);
>> +
>> + drm_master_internal_release(dev);
>> +unlock:
>> mutex_unlock(&fb_helper->lock);
>>
>> return ret;
>> @@ -2014,7 +2011,7 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
>> DRM_INFO("Cannot find any crtc or sizes\n");
>>
>> /* First time: disable all crtc's.. */
>> - if (!fb_helper->deferred_setup && !READ_ONCE(fb_helper->dev->master))
>> + if (!fb_helper->deferred_setup)
>> restore_fbdev_mode(fb_helper);
>> return -EAGAIN;
>> }
>> @@ -3028,6 +3025,7 @@ EXPORT_SYMBOL(drm_fb_helper_initial_config);
>> */
>> int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
>> {
>> + struct drm_device *dev = fb_helper->dev;
>> int err = 0;
>>
>> if (!drm_fbdev_emulation || !fb_helper)
>> @@ -3040,12 +3038,14 @@ int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
>> return err;
>> }
>>
>> - if (!fb_helper->fb || !drm_fb_helper_is_bound(fb_helper)) {
>> + if (!fb_helper->fb || !drm_master_internal_acquire(dev)) {
>> fb_helper->delayed_hotplug = true;
>> mutex_unlock(&fb_helper->lock);
>> return err;
>> }
>>
>> + drm_master_internal_release(dev);
>> +
>> DRM_DEBUG_KMS("\n");
>>
>> drm_setup_crtcs(fb_helper, fb_helper->fb->width, fb_helper->fb->height);
>> diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
>> index d9a483a5fce0..3ee97c9998a2 100644
>> --- a/drivers/gpu/drm/drm_internal.h
>> +++ b/drivers/gpu/drm/drm_internal.h
>> @@ -91,6 +91,8 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data,
>> struct drm_file *file_priv);
>> int drm_master_open(struct drm_file *file_priv);
>> void drm_master_release(struct drm_file *file_priv);
>> +bool drm_master_internal_acquire(struct drm_device *dev);
>> +void drm_master_internal_release(struct drm_device *dev);
>>
>> /* drm_sysfs.c */
>> extern struct class *drm_class;
>>
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
More information about the Intel-gfx
mailing list