Re: [PATCH 22/51] drm: manage drm_minor cleanup with drmm_

From: Daniel Vetter <daniel.vetter@ffwll.ch>
To: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>,
	Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	DRI Development <dri-devel@lists.freedesktop.org>,
	Daniel Vetter <daniel.vetter@intel.com>
Subject: Re: [PATCH 22/51] drm: manage drm_minor cleanup with drmm_
Date: Wed, 25 Mar 2020 10:07:08 +0100	[thread overview]
Message-ID: <CAKMK7uEu2=EV_Pg+vhANnFrAJMLfY8mEm35YCco6zbEHMP8dxw@mail.gmail.com> (raw)
In-Reply-To: <20200324213639.GB24902@ravnborg.org>

On Tue, Mar 24, 2020 at 10:36 PM Sam Ravnborg <sam@ravnborg.org> wrote:
>
> On Mon, Mar 23, 2020 at 03:49:21PM +0100, Daniel Vetter wrote:
> > The cleanup here is somewhat tricky, since we can't tell apart the
> > allocated minor index from 0. So register a cleanup action first, and
> > if the index allocation fails, unregister that cleanup action again to
> > avoid bad mistakes.
> >
> > The kdev for the minor already handles NULL, so no problem there.
> >
> > Hence add drmm_remove_action() to the drm_managed library.
> >
> > v2: Make pointer math around void ** consistent with what Laurent
> > suggested.
> >
> > v3: Use drmm_add_action_or_reset and remove drmm_remove_action. Noticed
> > because of some questions from Thomas. This also means we need to move
> > the drmm_add_action_or_reset helper earlier in the series.
> >
> > Cc: Thomas Zimmermann <tzimmermann@suse.de>
> > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > ---
> >  drivers/gpu/drm/drm_drv.c     | 70 ++++++++++++-----------------------
> >  drivers/gpu/drm/drm_managed.c | 14 +++++++
> >  include/drm/drm_managed.h     |  9 ++++-
> >  3 files changed, 46 insertions(+), 47 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> > index a710c53d13a8..25fc2107057c 100644
> > --- a/drivers/gpu/drm/drm_drv.c
> > +++ b/drivers/gpu/drm/drm_drv.c
> > @@ -93,13 +93,25 @@ static struct drm_minor **drm_minor_get_slot(struct drm_device *dev,
> >       }
> >  }
> >
> > +static void drm_minor_alloc_release(struct drm_device *dev, void *data)
> > +{
> > +     struct drm_minor *minor = data;
> > +     unsigned long flags;
> > +
> > +     put_device(minor->kdev);
> > +
> > +     spin_lock_irqsave(&drm_minor_lock, flags);
> > +     idr_remove(&drm_minors_idr, minor->index);
> > +     spin_unlock_irqrestore(&drm_minor_lock, flags);
> > +}
> > +
> >  static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
> >  {
> >       struct drm_minor *minor;
> >       unsigned long flags;
> >       int r;
> >
> > -     minor = kzalloc(sizeof(*minor), GFP_KERNEL);
> > +     minor = drmm_kzalloc(dev, sizeof(*minor), GFP_KERNEL);
> >       if (!minor)
> >               return -ENOMEM;
> >
> > @@ -117,46 +129,19 @@ static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
> >       idr_preload_end();
> >
> >       if (r < 0)
> > -             goto err_free;
> > +             return r;
> >
> > -     minor->index = r;
> > +     r = drmm_add_action_or_reset(dev, drm_minor_alloc_release, minor);
> > +     if (r)
> > +             return r;
> >
> > +     minor->index = r;
>
> This looks wrong.
>
> We do:
>         r = idr_alloc(&drm_minors_idr,
>
>         And then we loose the value when we reuse r
>         in the call to drmm_add_action_or_reset().
>         So the index we assign is the return value of
>         drmm_add_action_or_reset() and not the ID returned
>         by idr_alloc()
>
> With this fixed:
>
> Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
>
> >       minor->kdev = drm_sysfs_minor_alloc(minor);
> > -     if (IS_ERR(minor->kdev)) {
> > -             r = PTR_ERR(minor->kdev);
> > -             goto err_index;
> > -     }
> > +     if (IS_ERR(minor->kdev))
> > +             return PTR_ERR(minor->kdev);
> >
> >       *drm_minor_get_slot(dev, type) = minor;
> >       return 0;
> > -
> > -err_index:
> > -     spin_lock_irqsave(&drm_minor_lock, flags);
> > -     idr_remove(&drm_minors_idr, minor->index);
> > -     spin_unlock_irqrestore(&drm_minor_lock, flags);
> > -err_free:
> > -     kfree(minor);
> > -     return r;
> > -}
> > -
> > -static void drm_minor_free(struct drm_device *dev, unsigned int type)
> > -{
> > -     struct drm_minor **slot, *minor;
> > -     unsigned long flags;
> > -
> > -     slot = drm_minor_get_slot(dev, type);
> > -     minor = *slot;
> > -     if (!minor)
> > -             return;
> > -
> > -     put_device(minor->kdev);
> > -
> > -     spin_lock_irqsave(&drm_minor_lock, flags);
> > -     idr_remove(&drm_minors_idr, minor->index);
> > -     spin_unlock_irqrestore(&drm_minor_lock, flags);
> > -
> > -     kfree(minor);
> > -     *slot = NULL;
> >  }
> >
> >  static int drm_minor_register(struct drm_device *dev, unsigned int type)
> > @@ -678,16 +663,16 @@ int drm_dev_init(struct drm_device *dev,
> >       if (drm_core_check_feature(dev, DRIVER_RENDER)) {
> >               ret = drm_minor_alloc(dev, DRM_MINOR_RENDER);
> >               if (ret)
> > -                     goto err_minors;
> > +                     goto err;
> >       }
> >
> >       ret = drm_minor_alloc(dev, DRM_MINOR_PRIMARY);
> >       if (ret)
> > -             goto err_minors;
> > +             goto err;
> >
> >       ret = drm_legacy_create_map_hash(dev);
> >       if (ret)
> > -             goto err_minors;
> > +             goto err;
> >
> >       drm_legacy_ctxbitmap_init(dev);
> >
> > @@ -695,7 +680,7 @@ int drm_dev_init(struct drm_device *dev,
> >               ret = drm_gem_init(dev);
> >               if (ret) {
> >                       DRM_ERROR("Cannot initialize graphics execution manager (GEM)\n");
> > -                     goto err_ctxbitmap;
> > +                     goto err;
> >               }
> >       }
> >
> > @@ -708,10 +693,6 @@ int drm_dev_init(struct drm_device *dev,
> >  err_setunique:
> >       if (drm_core_check_feature(dev, DRIVER_GEM))
> >               drm_gem_destroy(dev);
> > -err_ctxbitmap:
> > -err_minors:
> > -     drm_minor_free(dev, DRM_MINOR_PRIMARY);
> > -     drm_minor_free(dev, DRM_MINOR_RENDER);
> >  err:
> >       drm_managed_release(dev);
> >
> > @@ -776,9 +757,6 @@ void drm_dev_fini(struct drm_device *dev)
> >
> >       if (drm_core_check_feature(dev, DRIVER_GEM))
> >               drm_gem_destroy(dev);
> > -
> > -     drm_minor_free(dev, DRM_MINOR_PRIMARY);
> > -     drm_minor_free(dev, DRM_MINOR_RENDER);
> >  }
> >  EXPORT_SYMBOL(drm_dev_fini);
> >
> > diff --git a/drivers/gpu/drm/drm_managed.c b/drivers/gpu/drm/drm_managed.c
> > index c633c2ef5269..8abf3a53aeb5 100644
> > --- a/drivers/gpu/drm/drm_managed.c
> > +++ b/drivers/gpu/drm/drm_managed.c
> > @@ -149,6 +149,20 @@ int __drmm_add_action(struct drm_device *dev,
> >  }
> >  EXPORT_SYMBOL(__drmm_add_action);
> >
> > +int __drmm_add_action_or_reset(struct drm_device *dev,
> > +                            drmres_release_t action,
> > +                            void *data, const char *name)
> > +{
> > +     int ret;
> > +
> > +     ret = __drmm_add_action(dev, action, data, name);
> > +     if (ret)
> > +             action(dev, data);
> > +
> > +     return ret;
> > +}
> > +EXPORT_SYMBOL(__drmm_add_action_or_reset);
> > +
> >  void *drmm_kmalloc(struct drm_device *dev, size_t size, gfp_t gfp)
> >  {
> >       struct drmres *dr;
> > diff --git a/include/drm/drm_managed.h b/include/drm/drm_managed.h
> > index 89e6fce9f689..2d1e29a2200c 100644
> > --- a/include/drm/drm_managed.h
> > +++ b/include/drm/drm_managed.h
> > @@ -17,7 +17,14 @@ int __must_check __drmm_add_action(struct drm_device *dev,
> >                                  drmres_release_t action,
> >                                  void *data, const char *name);
> >
> > -void drmm_add_final_kfree(struct drm_device *dev, void *parent);
> > +#define drmm_add_action_or_reset(dev, action, data) \
> > +     __drmm_add_action_or_reset(dev, action, data, #action)
> > +
> > +int __must_check __drmm_add_action_or_reset(struct drm_device *dev,
> > +                                         drmres_release_t action,
> > +                                         void *data, const char *name);
> > +
> > +void drmm_add_final_kfree(struct drm_device *dev, void *container);
> There is a s/parent/container/ sneaked in here???

Uh rebase fail, I'll try to move this to the right patch.
s/parent/container/ was requested by Thomas to clarify the meaning,
but looks like the fixup ended up in the wrong place :-/
-Daniel

>
> >
> >  void *drmm_kmalloc(struct drm_device *dev, size_t size, gfp_t gfp) __malloc;
> >  static inline void *drmm_kzalloc(struct drm_device *dev, size_t size, gfp_t gfp)
> > --
> > 2.25.1
> >
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel


-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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