From: Brendan King Brendan.King@imgtec.com

Do scheduler queue fence release processing on a workqueue, rather than in the release function itself.

Fixes deadlock issues such as the following:

[ 607.400437] ============================================ [ 607.405755] WARNING: possible recursive locking detected [ 607.415500] -------------------------------------------- [ 607.420817] weston:zfq0/24149 is trying to acquire lock: [ 607.426131] ffff000017d041a0 (reservation_ww_class_mutex){+.+.}-{3:3}, at: pvr_gem_object_vunmap+0x40/0xc0 [powervr] [ 607.436728] but task is already holding lock: [ 607.442554] ffff000017d105a0 (reservation_ww_class_mutex){+.+.}-{3:3}, at: dma_buf_ioctl+0x250/0x554 [ 607.451727] other info that might help us debug this: [ 607.458245] Possible unsafe locking scenario:

[ 607.464155] CPU0 [ 607.466601] ---- [ 607.469044] lock(reservation_ww_class_mutex); [ 607.473584] lock(reservation_ww_class_mutex); [ 607.478114] *** DEADLOCK ***

Cc: stable@vger.kernel.org Fixes: eaf01ee5ba28 ("drm/imagination: Implement job submission and scheduling") Signed-off-by: Brendan King brendan.king@imgtec.com --- Changes in v2: - Added 'Cc:' and 'Fixes:' tags - Link to v1: https://lore.kernel.org/r/20250203-fence-release-deadlock-v1-1-6e1de1260b38@... --- drivers/gpu/drm/imagination/pvr_queue.c | 13 +++++++++++-- drivers/gpu/drm/imagination/pvr_queue.h | 4 ++++ 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/imagination/pvr_queue.c b/drivers/gpu/drm/imagination/pvr_queue.c index c4f08432882b12f5cdfeb7fc991fd941f0946676..f3f1c5212df7432161919ddc510cececacbbe143 100644 --- a/drivers/gpu/drm/imagination/pvr_queue.c +++ b/drivers/gpu/drm/imagination/pvr_queue.c @@ -109,12 +109,20 @@ pvr_queue_fence_get_driver_name(struct dma_fence *f) return PVR_DRIVER_NAME; }

+static void pvr_queue_fence_release_work(struct work_struct *w) +{ + struct pvr_queue_fence *fence = container_of(w, struct pvr_queue_fence, release_work); + + pvr_context_put(fence->queue->ctx); + dma_fence_free(&fence->base); +} + static void pvr_queue_fence_release(struct dma_fence *f) { struct pvr_queue_fence *fence = container_of(f, struct pvr_queue_fence, base); + struct pvr_device *pvr_dev = fence->queue->ctx->pvr_dev;

- pvr_context_put(fence->queue->ctx); - dma_fence_free(f); + queue_work(pvr_dev->sched_wq, &fence->release_work); }

static const char * @@ -268,6 +276,7 @@ pvr_queue_fence_init(struct dma_fence *f,

pvr_context_get(queue->ctx); fence->queue = queue; + INIT_WORK(&fence->release_work, pvr_queue_fence_release_work); dma_fence_init(&fence->base, fence_ops, &fence_ctx->lock, fence_ctx->id, atomic_inc_return(&fence_ctx->seqno)); diff --git a/drivers/gpu/drm/imagination/pvr_queue.h b/drivers/gpu/drm/imagination/pvr_queue.h index e06ced69302fca47fc26451dfb09ebbb24b57f52..93fe9ac9f58ccc020615485e86be438548dcee43 100644 --- a/drivers/gpu/drm/imagination/pvr_queue.h +++ b/drivers/gpu/drm/imagination/pvr_queue.h @@ -5,6 +5,7 @@ #define PVR_QUEUE_H

#include <drm/gpu_scheduler.h> +#include <linux/workqueue.h>

#include "pvr_cccb.h" #include "pvr_device.h" @@ -63,6 +64,9 @@ struct pvr_queue_fence {

/** @queue: Queue that created this fence. */ struct pvr_queue *queue; + + /** @release_work: Fence release work structure. */ + struct work_struct release_work; };

/**

--- base-commit: 3ab334814dc7dff39075e055e12847d51878916e change-id: 20250203-fence-release-deadlock-a0753c07bfdd

Best regards,