[PATCH v2 11/23] drm/msm: Use idr_preload()

Rob Clark
2023-03-20T14:45:23Z

Avoid allocation under idr_lock, to prevent deadlock against the
job_free() path (which runs on same thread as job_run(), which makes
it also part of the fence-signaling path.

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
drivers/gpu/drm/msm/msm_gem_submit.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
index b9d81e5acb42..0ab62cb4ed69 100644
--- a/drivers/gpu/drm/msm/msm_gem_submit.c
+++ b/drivers/gpu/drm/msm/msm_gem_submit.c
@@ -882,6 +882,8 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,

submit->nr_cmds = i;

+ idr_preload(GFP_KERNEL);
+
spin_lock(&queue->idr_lock);

/*
@@ -893,6 +895,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
if ((args->flags & MSM_SUBMIT_FENCE_SN_IN) &&
idr_find(&queue->fence_idr, args->fence)) {
spin_unlock(&queue->idr_lock);
+ idr_preload_end();
ret = -EINVAL;
goto out;
}
@@ -910,7 +913,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
submit->fence_id = args->fence;
ret = idr_alloc_u32(&queue->fence_idr, submit->user_fence,
&submit->fence_id, submit->fence_id,
- GFP_KERNEL);
+ GFP_NOWAIT);
/*
* We've already validated that the fence_id slot is valid,
* so if idr_alloc_u32 failed, it is a kernel bug
@@ -923,10 +926,11 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
*/
submit->fence_id = idr_alloc_cyclic(&queue->fence_idr,
submit->user_fence, 1,
- INT_MAX, GFP_KERNEL);
+ INT_MAX, GFP_NOWAIT);
}

spin_unlock(&queue->idr_lock);
+ idr_preload_end();

if (submit->fence_id < 0) {
ret = submit->fence_id;
--
2.39.2