From nobody Thu Dec 18 02:24:25 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 56AF126137B for ; Mon, 24 Mar 2025 18:59:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742842776; cv=none; b=JCjld54T6QsMIjcQmtqDP8QxXjZcaRt6piWIS0OD5hM0f0GIMhrDYHQFuCbym24oSf1z7d+u36jOAzTTa0YejRPE11CwhKD3P4P5BBN24Nw3mNlYP1e76K9XPbwG8mXBjb+eOm1XTJGUVONqI3PgT6Gzdhz+Xc3MvSHS3jXJhX8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742842776; c=relaxed/simple; bh=LNb2F2c8zejJK69+mIOoiRybsoWajBLMqCUkOY1Wo0Q=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JoOJxKjYn/WCYHUmO8P9XN8R5frd2FqWtOsw76nXNOY3NcrkutOeO3lL9GT9mUf3H7JI/l9Kru1zw3rt0WQD5HoVfP5pmytb1GDfVPrzQ6uc+//3082gEpAQ882DlhNzy1/00raQzjojYAtYKwMdQ5RrouIUN/xSCwrxnZn7yRE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=e182ef8e; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="e182ef8e" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2B32CC4CEDD; Mon, 24 Mar 2025 18:59:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742842774; bh=LNb2F2c8zejJK69+mIOoiRybsoWajBLMqCUkOY1Wo0Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=e182ef8ede+irYinDn6XTciN4Ex31PqrioQgd73OedFXW6CnCknDLmOJtTNynMg/e lTR0qjVFMhS0c4RyEJ/pw1KDZmmO7KVLwfUI6pPXyeGixfxYPvj6xpdMRJbV5lofJ0 seWPT6drG7wpXKqUQkiipOO6Qh4iTdvEe3HlkboCD9hRv922rGjMcFjg4xfW0L0VMu vKsuVcT7hzGJy1/Z6a5DIwBuGhRcPaQzXF62dCUwjPBueYBhSS7aJMh9oxhuVa6dmT bS8B+J/+aevKaDQpBcMhHYNO93SCgllyqcZsO2Hxn42rWx3fI5Ut+ZZ1Zmm1myFqbS 3hcrG/+F4jeyg== From: Philipp Stanner To: Lyude Paul , Danilo Krummrich , David Airlie , Simona Vetter , Matthew Brost , Philipp Stanner , =?UTF-8?q?Christian=20K=C3=B6nig?= , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Tvrtko Ursulin Cc: dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, linux-kernel@vger.kernel.org, Danilo Krummrich Subject: [RFC PATCH 2/5] drm/sched: Prevent teardown waitque from blocking too long Date: Mon, 24 Mar 2025 19:57:26 +0100 Message-ID: <20250324185728.45857-4-phasta@kernel.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250324185728.45857-2-phasta@kernel.org> References: <20250324185728.45857-2-phasta@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The waitqueue that ensures that drm_sched_fini() blocks until the pending_list has become empty could theoretically cause that function to block for a very long time. That, ultimately, could block userspace procesess and prevent them from being killable through SIGKILL. When a driver calls drm_sched_fini(), it is safe to assume that all still pending jobs are not needed anymore anyways. Thus, they can be cancelled and thereby it can be ensured that drm_sched_fini() will return relatively quickly. Implement a new helper to stop all work items / submission except for the drm_sched_backend_ops.run_job(). Implement a driver callback, kill_fence_context(), that instructs the driver to kill the fence context associated with this scheduler, thereby causing all pending hardware fences to be signalled. Call those new routines in drm_sched_fini() and ensure backwards compatibility if the new callback is not implemented. Suggested-by: Danilo Krummrich Signed-off-by: Philipp Stanner --- drivers/gpu/drm/scheduler/sched_main.c | 47 +++++++++++++++++--------- include/drm/gpu_scheduler.h | 11 ++++++ 2 files changed, 42 insertions(+), 16 deletions(-) diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/sched= uler/sched_main.c index c1ab48ef61cf..87acbcb1a821 100644 --- a/drivers/gpu/drm/scheduler/sched_main.c +++ b/drivers/gpu/drm/scheduler/sched_main.c @@ -1388,31 +1388,46 @@ drm_sched_no_jobs_pending(struct drm_gpu_scheduler = *sched) return empty; } =20 +/** + * drm_sched_cancel_jobs_and_wait - trigger freeing of all pending jobs + * @sched: scheduler instance + * + * Must only be called if &struct drm_sched_backend_ops.kill_fence_context= is + * implemented. + * + * Instructs the driver to kill the fence context associated with this sch= eduler, + * thereby signalling all pending fences. This, in turn, will trigger + * &struct drm_sched_backend_ops.free_job to be called for all pending job= s. + * The function then blocks until all pending jobs have been freed. + */ +static inline void +drm_sched_cancel_jobs_and_wait(struct drm_gpu_scheduler *sched) +{ + sched->ops->kill_fence_context(sched); + wait_event(sched->pending_list_waitque, drm_sched_no_jobs_pending(sched)); +} + /** * drm_sched_fini - Destroy a gpu scheduler * * @sched: scheduler instance * - * Tears down and cleans up the scheduler. - * - * Note that this function blocks until all the fences returned by - * &struct drm_sched_backend_ops.run_job have been signalled. + * Tears down and cleans up the scheduler. Might leak memory if + * &struct drm_sched_backend_ops.kill_fence_context is not implemented. */ void drm_sched_fini(struct drm_gpu_scheduler *sched) { struct drm_sched_entity *s_entity; int i; =20 - /* - * Jobs that have neither been scheduled or which have timed out are - * gone by now, but jobs that have been submitted through - * backend_ops.run_job() and have not yet terminated are still pending. - * - * Wait for the pending_list to become empty to avoid leaking those jobs. - */ - drm_sched_submission_and_timeout_stop(sched); - wait_event(sched->pending_list_waitque, drm_sched_no_jobs_pending(sched)); - drm_sched_free_stop(sched); + if (sched->ops->kill_fence_context) { + drm_sched_submission_and_timeout_stop(sched); + drm_sched_cancel_jobs_and_wait(sched); + drm_sched_free_stop(sched); + } else { + /* We're in "legacy free-mode" and ignore potential mem leaks */ + drm_sched_wqueue_stop(sched); + } =20 for (i =3D DRM_SCHED_PRIORITY_KERNEL; i < sched->num_rqs; i++) { struct drm_sched_rq *rq =3D sched->sched_rq[i]; @@ -1500,7 +1515,7 @@ bool drm_sched_wqueue_ready(struct drm_gpu_scheduler = *sched) EXPORT_SYMBOL(drm_sched_wqueue_ready); =20 /** - * drm_sched_wqueue_stop - stop scheduler submission + * drm_sched_wqueue_stop - stop scheduler submission and freeing * @sched: scheduler instance * * Stops the scheduler from pulling new jobs from entities. It also stops @@ -1516,7 +1531,7 @@ void drm_sched_wqueue_stop(struct drm_gpu_scheduler *= sched) EXPORT_SYMBOL(drm_sched_wqueue_stop); =20 /** - * drm_sched_wqueue_start - start scheduler submission + * drm_sched_wqueue_start - start scheduler submission and freeing * @sched: scheduler instance * * Restarts the scheduler after drm_sched_wqueue_stop() has stopped it. diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h index badcf9ea4501..e13eb7e4c93a 100644 --- a/include/drm/gpu_scheduler.h +++ b/include/drm/gpu_scheduler.h @@ -509,6 +509,17 @@ struct drm_sched_backend_ops { * and it's time to clean it up. */ void (*free_job)(struct drm_sched_job *sched_job); + + /** + * @kill_fence_context: kill the fence context belonging to this scheduler + * + * Needed to cleanly tear the scheduler down in drm_sched_fini(). This + * callback will cause all hardware fences to be signalled by the driver, + * which, ultimately, ensures that all jobs get freed before teardown. + * + * This callback is optional, but it is highly recommended to implement i= t. + */ + void (*kill_fence_context)(struct drm_gpu_scheduler *sched); }; =20 /** --=20 2.48.1