| Message ID | 20190407165243.54043-3-noralf@tronnes.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/fb-helper: Move modesetting code to drm_client | expand |
On Sun, Apr 07, 2019 at 06:52:33PM +0200, Noralf Trønnes wrote: > 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@ffwll.ch> > Signed-off-by: Noralf Trønnes <noralf@tronnes.org> > --- > 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 84791dd4a90d..a6be09ae899b 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) Bikeshed: usually the function variant that's run with locks already taken is called _locked or has a __ prefix. _force feels a bit misplaced. > { > 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 > @@ -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); I'd leave this as-is, because: a) I'm too lazy to review the locking of our open/close calls to convince myself that lastclose can't race with the next open b) it won't hurt c) leaves the door open to easily make our open/close more concurrent in the future > 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); I think we need to return the errno here, since without that the higher levels won't reprobe correctly. Plus we need to remap -EBUSY to -EAGAIN (or change the check in __drm_fb_helper_initial_config_and_unlock to also retry on -EBUSY). > return -EAGAIN; > } > @@ -2842,6 +2839,7 @@ 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) > @@ -2854,12 +2852,14 @@ 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; With the nits addressed: Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> > -- > 2.20.1 >
On Sun, Apr 07, 2019 at 06:52:33PM +0200, Noralf Trønnes wrote: > 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@ffwll.ch> > Signed-off-by: Noralf Trønnes <noralf@tronnes.org> With the changes asked by Daniel, Reviewed-by: Maxime Ripard <maxime.ripard@bootlin.com> Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
Den 16.04.2019 09.59, skrev Daniel Vetter: > On Sun, Apr 07, 2019 at 06:52:33PM +0200, Noralf Trønnes wrote: >> 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@ffwll.ch> >> Signed-off-by: Noralf Trønnes <noralf@tronnes.org> >> --- >> 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 84791dd4a90d..a6be09ae899b 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) > > Bikeshed: usually the function variant that's run with locks already taken > is called _locked or has a __ prefix. _force feels a bit misplaced. This isn't a _locked function in the usual sense, it is: apply modeset even if there is a DRM master. So we are _forcing a modeset on a possibly unexpecting DRM userspace. To me a _locked function would imply that the caller _must_ take a lock in order to use it. But no big deal, I can rename it _locked if that reads better. After a few years of reading kernel code I've come to appreciate the consistency in how things are done and named. Every time things are different it slows down my internal logic/pattern parser. >> { >> 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 >> @@ -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); > > I'd leave this as-is, because: > a) I'm too lazy to review the locking of our open/close calls to convince > myself that lastclose can't race with the next open > b) it won't hurt > c) leaves the door open to easily make our open/close more concurrent in > the future > I'm not actually changing anything here, it's restore_fbdev_mode() that has changed, it now bails out if there's a DRM master. If we don't change this to _force/_locked, then sysrq won't work if there's a DRM master. Which kind of defeats the whole idea of this 'give me fbcon right now' functionality doesn't it? >> 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); > > I think we need to return the errno here, since without that the higher > levels won't reprobe correctly. Plus we need to remap -EBUSY to -EAGAIN > (or change the check in __drm_fb_helper_initial_config_and_unlock to also > retry on -EBUSY). > I don't think so, because -EAGAIN is returned unconditionally on the line below. The restore_fbdev_mode() call is just to disable the outputs _if_ there's no DRM master, which that function now checks for. Noralf. >> return -EAGAIN; >> } >> @@ -2842,6 +2839,7 @@ 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) >> @@ -2854,12 +2852,14 @@ 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; > > With the nits addressed: > > Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> > >> -- >> 2.20.1 >> >
On Tue, Apr 16, 2019 at 08:46:24PM +0200, Noralf Trønnes wrote: > > > Den 16.04.2019 09.59, skrev Daniel Vetter: > > On Sun, Apr 07, 2019 at 06:52:33PM +0200, Noralf Trønnes wrote: > >> 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@ffwll.ch> > >> Signed-off-by: Noralf Trønnes <noralf@tronnes.org> > >> --- > >> 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 84791dd4a90d..a6be09ae899b 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) > > > > Bikeshed: usually the function variant that's run with locks already taken > > is called _locked or has a __ prefix. _force feels a bit misplaced. > > This isn't a _locked function in the usual sense, it is: apply modeset > even if there is a DRM master. So we are _forcing a modeset on a > possibly unexpecting DRM userspace. To me a _locked function would imply > that the caller _must_ take a lock in order to use it. Hm, good point. See my comments later on, I'm not sure the "forcing" is really what we want. I think lastclose would be much better served if it also checks for master status. > But no big deal, I can rename it _locked if that reads better. After a > few years of reading kernel code I've come to appreciate the consistency > in how things are done and named. Every time things are different it > slows down my internal logic/pattern parser. If you agree with the entire "we should _force" then I think the __ prefix would fit. It's the general "beware, this is special/internal" annotation. My _locked suggestion was under the assumption that there's never a real case where we want to do the unprotected modeset for an internal drm_client. > >> { > >> 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 > >> @@ -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); > > > > I'd leave this as-is, because: > > a) I'm too lazy to review the locking of our open/close calls to convince > > myself that lastclose can't race with the next open > > b) it won't hurt > > c) leaves the door open to easily make our open/close more concurrent in > > the future > > > > I'm not actually changing anything here, it's restore_fbdev_mode() that > has changed, it now bails out if there's a DRM master. If we don't > change this to _force/_locked, then sysrq won't work if there's a DRM > master. Which kind of defeats the whole idea of this 'give me fbcon > right now' functionality doesn't it? Uh, I was blind, I thought this was for lastclose. With this one here I think _force makes sense. I still think that the main drm_client_modeset interface should be the normal one which checks for master for you. > >> 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); > > > > I think we need to return the errno here, since without that the higher > > levels won't reprobe correctly. Plus we need to remap -EBUSY to -EAGAIN > > (or change the check in __drm_fb_helper_initial_config_and_unlock to also > > retry on -EBUSY). > > > > I don't think so, because -EAGAIN is returned unconditionally on the > line below. The restore_fbdev_mode() call is just to disable the outputs > _if_ there's no DRM master, which that function now checks for. Hm right, my logic parser went *boink* I think. Looks good on 2nd reading. -Daniel > > Noralf. > > >> return -EAGAIN; > >> } > >> @@ -2842,6 +2839,7 @@ 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) > >> @@ -2854,12 +2852,14 @@ 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; > > > > With the nits addressed: > > > > Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> > > > >> -- > >> 2.20.1 > >> > >
On Wed, Apr 17, 2019 at 03:24:00PM +0200, Daniel Vetter wrote: > On Tue, Apr 16, 2019 at 08:46:24PM +0200, Noralf Trønnes wrote: > > > > > > Den 16.04.2019 09.59, skrev Daniel Vetter: > > > On Sun, Apr 07, 2019 at 06:52:33PM +0200, Noralf Trønnes wrote: > > >> 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@ffwll.ch> > > >> Signed-off-by: Noralf Trønnes <noralf@tronnes.org> > > >> --- > > >> 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 84791dd4a90d..a6be09ae899b 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) > > > > > > Bikeshed: usually the function variant that's run with locks already taken > > > is called _locked or has a __ prefix. _force feels a bit misplaced. > > > > This isn't a _locked function in the usual sense, it is: apply modeset > > even if there is a DRM master. So we are _forcing a modeset on a > > possibly unexpecting DRM userspace. To me a _locked function would imply > > that the caller _must_ take a lock in order to use it. > > Hm, good point. See my comments later on, I'm not sure the "forcing" is > really what we want. I think lastclose would be much better served if it > also checks for master status. > > > But no big deal, I can rename it _locked if that reads better. After a > > few years of reading kernel code I've come to appreciate the consistency > > in how things are done and named. Every time things are different it > > slows down my internal logic/pattern parser. > > If you agree with the entire "we should _force" then I think the __ prefix > would fit. It's the general "beware, this is special/internal" annotation. > My _locked suggestion was under the assumption that there's never a real > case where we want to do the unprotected modeset for an internal > drm_client. > > > >> { > > >> 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 > > >> @@ -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); > > > > > > I'd leave this as-is, because: > > > a) I'm too lazy to review the locking of our open/close calls to convince > > > myself that lastclose can't race with the next open > > > b) it won't hurt > > > c) leaves the door open to easily make our open/close more concurrent in > > > the future > > > > > > > I'm not actually changing anything here, it's restore_fbdev_mode() that > > has changed, it now bails out if there's a DRM master. If we don't > > change this to _force/_locked, then sysrq won't work if there's a DRM > > master. Which kind of defeats the whole idea of this 'give me fbcon > > right now' functionality doesn't it? > > Uh, I was blind, I thought this was for lastclose. With this one here I > think _force makes sense. I still think that the main drm_client_modeset > interface should be the normal one which checks for master for you. Ok, I read the later patches and you already have a commit() and a commit_force(). Count me convinced on all points. Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> as-is on this patch. Cheers, Daniel > > > >> 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); > > > > > > I think we need to return the errno here, since without that the higher > > > levels won't reprobe correctly. Plus we need to remap -EBUSY to -EAGAIN > > > (or change the check in __drm_fb_helper_initial_config_and_unlock to also > > > retry on -EBUSY). > > > > > > > I don't think so, because -EAGAIN is returned unconditionally on the > > line below. The restore_fbdev_mode() call is just to disable the outputs > > _if_ there's no DRM master, which that function now checks for. > > Hm right, my logic parser went *boink* I think. Looks good on 2nd reading. > -Daniel > > > > Noralf. > > > > >> return -EAGAIN; > > >> } > > >> @@ -2842,6 +2839,7 @@ 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) > > >> @@ -2854,12 +2852,14 @@ 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; > > > > > > With the nits addressed: > > > > > > Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> > > > > > >> -- > > >> 2.20.1 > > >> > > > > > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch
Den 17.04.2019 15.26, skrev Daniel Vetter: > On Wed, Apr 17, 2019 at 03:24:00PM +0200, Daniel Vetter wrote: >> On Tue, Apr 16, 2019 at 08:46:24PM +0200, Noralf Trønnes wrote: >>> >>> >>> Den 16.04.2019 09.59, skrev Daniel Vetter: >>>> On Sun, Apr 07, 2019 at 06:52:33PM +0200, Noralf Trønnes wrote: >>>>> 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@ffwll.ch> >>>>> Signed-off-by: Noralf Trønnes <noralf@tronnes.org> >>>>> --- <snip> > Ok, I read the later patches and you already have a commit() and a > commit_force(). Count me convinced on all points. > > Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> > > as-is on this patch. > Thanks. I want to apply this after the for-5.2 cutoff so we can get some testing on this before it hits the world. I know from the timeline chart that the cutoff is some time after -rc5, but I don't know _excatly_ when that is. I looked at dim, but all I could glean from it was that it had something to do with the state of a -fixes branch. Noralf.
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 84791dd4a90d..a6be09ae899b 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 @@ -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; } @@ -2842,6 +2839,7 @@ 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) @@ -2854,12 +2852,14 @@ 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;
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@ffwll.ch> Signed-off-by: Noralf Trønnes <noralf@tronnes.org> --- 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(-)