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Thu, 22 Jul 2021 03:38:11 -0700 (PDT) Date: Thu, 22 Jul 2021 12:38:10 +0200 From: Daniel Vetter To: Desmond Cheong Zhi Xi , Boqun Feng , LKML , Peter Zijlstra Message-ID: Mail-Followup-To: Desmond Cheong Zhi Xi , Boqun Feng , LKML , Peter Zijlstra , linux-graphics-maintainer@vmware.com, zackr@vmware.com, airlied@linux.ie, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, skhan@linuxfoundation.org, gregkh@linuxfoundation.org, linux-kernel-mentees@lists.linuxfoundation.org References: <20210722092929.244629-1-desmondcheongzx@gmail.com> <20210722092929.244629-2-desmondcheongzx@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210722092929.244629-2-desmondcheongzx@gmail.com> X-Operating-System: Linux phenom 5.10.0-7-amd64 Subject: Re: [Intel-gfx] [PATCH 1/3] drm: use the lookup lock in drm_is_current_master X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: tzimmermann@suse.de, airlied@linux.ie, gregkh@linuxfoundation.org, intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, mripard@kernel.org, Daniel Vetter , linux-graphics-maintainer@vmware.com, dri-devel@lists.freedesktop.org, skhan@linuxfoundation.org, linux-kernel-mentees@lists.linuxfoundation.org, zackr@vmware.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Thu, Jul 22, 2021 at 05:29:27PM +0800, Desmond Cheong Zhi Xi wrote: > Inside drm_is_current_master, using the outer drm_device.master_mutex > to protect reads of drm_file.master makes the function prone to creating > lock hierarchy inversions. Instead, we can use the > drm_file.master_lookup_lock that sits at the bottom of the lock > hierarchy. > > Reported-by: Daniel Vetter > Signed-off-by: Desmond Cheong Zhi Xi > --- > drivers/gpu/drm/drm_auth.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c > index f00354bec3fb..9c24b8cc8e36 100644 > --- a/drivers/gpu/drm/drm_auth.c > +++ b/drivers/gpu/drm/drm_auth.c > @@ -63,8 +63,9 @@ > > static bool drm_is_current_master_locked(struct drm_file *fpriv) > { > - lockdep_assert_held_once(&fpriv->minor->dev->master_mutex); > - > + /* Either drm_device.master_mutex or drm_file.master_lookup_lock > + * should be held here. > + */ Disappointing that lockdep can't check or conditions for us, a lockdep_assert_held_either would be really neat in some cases. Adding lockdep folks, maybe they have ideas. On the patch: Reviewed-by: Daniel Vetter > return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; > } > > @@ -82,9 +83,9 @@ bool drm_is_current_master(struct drm_file *fpriv) > { > bool ret; > > - mutex_lock(&fpriv->minor->dev->master_mutex); > + spin_lock(&fpriv->master_lookup_lock); > ret = drm_is_current_master_locked(fpriv); > - mutex_unlock(&fpriv->minor->dev->master_mutex); > + spin_unlock(&fpriv->master_lookup_lock); > > return ret; > } > -- > 2.25.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx