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Mon, 14 Sep 2026 11:27:43 -0700 (PDT) From: "=?UTF-8?q?Christian=20K=C3=B6nig?=" X-Google-Original-From: =?UTF-8?q?Christian=20K=C3=B6nig?= To: phasta@kernel.org, malhyuk97@gmail.com, tursulin@ursulin.net, matthew.brost@intel.com, dakr@kernel.org Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, mdaenzer@redhat.com, alessio.belle@imgtec.com, luigi.santivetti@imgtec.com Subject: [PATCH 2/2] drm/sched: document the RCU dependency Date: Mon, 14 Sep 2026 20:27:40 +0200 Message-ID: <20260914182740.1587-2-christian.koenig@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260914182740.1587-1-christian.koenig@amd.com> References: <20260914182740.1587-1-christian.koenig@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Reply-To: christian.koenig@amd.com Content-Transfer-Encoding: 8bit Tvrkos patches added RCU protection to the returned strings from get_timeline_name()/get_driver_name() callbacks of the dma_fence backends. This fixed use after free problems for a couple of drivers, but we never documented the consequences for the drm_sched_fence. Add a few words on the function documentation to note that we need an RCU grace period between signaling the last scheduler fence and scheduler teardown. Signed-off-by: Christian König --- drivers/gpu/drm/scheduler/sched_main.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c index 6cb6f95464938..f73c5141b4e5c 100644 --- a/drivers/gpu/drm/scheduler/sched_main.c +++ b/drivers/gpu/drm/scheduler/sched_main.c @@ -1203,6 +1203,11 @@ static void drm_sched_cancel_remaining_jobs(struct drm_gpu_scheduler *sched) * is implemented, all jobs will be canceled through it and afterwards cleaned * up through &struct drm_sched_backend_ops.free_job. If cancel_job is not * implemented, memory could leak. + * + * The user must wait one RCU grace period between signaling the last hardware- + * fence and calling this function because the timeline name returned by + * scheduler fences must stay valid until all readers have exited their RCU read + * side critical section. */ void drm_sched_fini(struct drm_gpu_scheduler *sched) { -- 2.43.0