From 276dc5f9e39ba07fe5dd71d903cc67b5f39b59d8 Mon Sep 17 00:00:00 2001 From: Erico Nunes Date: Fri, 5 Apr 2024 17:29:51 +0200 Subject: [PATCH] drm/lima: mask irqs in timeout path before hard reset [ Upstream commit a421cc7a6a001b70415aa4f66024fa6178885a14 ] There is a race condition in which a rendering job might take just long enough to trigger the drm sched job timeout handler but also still complete before the hard reset is done by the timeout handler. This runs into race conditions not expected by the timeout handler. In some very specific cases it currently may result in a refcount imbalance on lima_pm_idle, with a stack dump such as: [10136.669170] WARNING: CPU: 0 PID: 0 at drivers/gpu/drm/lima/lima_devfreq.c:205 lima_devfreq_record_idle+0xa0/0xb0 ... [10136.669459] pc : lima_devfreq_record_idle+0xa0/0xb0 ... [10136.669628] Call trace: [10136.669634] lima_devfreq_record_idle+0xa0/0xb0 [10136.669646] lima_sched_pipe_task_done+0x5c/0xb0 [10136.669656] lima_gp_irq_handler+0xa8/0x120 [10136.669666] __handle_irq_event_percpu+0x48/0x160 [10136.669679] handle_irq_event+0x4c/0xc0 We can prevent that race condition entirely by masking the irqs at the beginning of the timeout handler, at which point we give up on waiting for that job entirely. The irqs will be enabled again at the next hard reset which is already done as a recovery by the timeout handler. Signed-off-by: Erico Nunes Reviewed-by: Qiang Yu Signed-off-by: Qiang Yu Link: https://patchwork.freedesktop.org/patch/msgid/20240405152951.1531555-4-nunes.erico@gmail.com Signed-off-by: Sasha Levin --- drivers/gpu/drm/lima/lima_sched.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/gpu/drm/lima/lima_sched.c b/drivers/gpu/drm/lima/lima_sched.c index f6e7a88a5..290f875c2 100755 --- a/drivers/gpu/drm/lima/lima_sched.c +++ b/drivers/gpu/drm/lima/lima_sched.c @@ -419,6 +419,13 @@ static void lima_sched_timedout_job(struct drm_sched_job *job) struct lima_sched_task *task = to_lima_task(job); struct lima_device *ldev = pipe->ldev; + /* + * The task might still finish while this timeout handler runs. + * To prevent a race condition on its completion, mask all irqs + * on the running core until the next hard reset completes. + */ + pipe->task_mask_irq(pipe); + if (!pipe->error) DRM_ERROR("lima job timeout\n");