Patch "drm/lima: mask irqs in timeout path before hard reset" has been added to the 6.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    drm/lima: mask irqs in timeout path before hard reset

to the 6.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-lima-mask-irqs-in-timeout-path-before-hard-reset.patch
and it can be found in the queue-6.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit b4ad08ed3d1a679f5cf8b27e0743e3fa7ef3a1cc
Author: Erico Nunes <nunes.erico@xxxxxxxxx>
Date:   Fri Apr 5 17:29:51 2024 +0200

    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 <nunes.erico@xxxxxxxxx>
    Reviewed-by: Qiang Yu <yuq825@xxxxxxxxx>
    Signed-off-by: Qiang Yu <yuq825@xxxxxxxxx>
    Link: https://patchwork.freedesktop.org/patch/msgid/20240405152951.1531555-4-nunes.erico@xxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/gpu/drm/lima/lima_sched.c b/drivers/gpu/drm/lima/lima_sched.c
index 66841503a6183..bbf3f8feab944 100644
--- a/drivers/gpu/drm/lima/lima_sched.c
+++ b/drivers/gpu/drm/lima/lima_sched.c
@@ -430,6 +430,13 @@ static enum drm_gpu_sched_stat lima_sched_timedout_job(struct drm_sched_job *job
 		return DRM_GPU_SCHED_STAT_NOMINAL;
 	}
 
+	/*
+	 * 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("%s job timeout\n", lima_ip_name(ip));