On 29-Mar-26 3:09 AM, Mikhail Gavrilov wrote:
Commit 14b81abe7bdc ("drm/amdgpu: prevent immediate PASID reuse case")
switched from ida to idr_alloc_cyclic() protected by a spinlock, but
passes GFP_KERNEL to the allocator. idr_alloc_cyclic() may need to
allocate radix-tree nodes, which with GFP_KERNEL can sleep — illegal
under a spinlock that disables preemption. With CONFIG_PREEMPT or
lockdep enabled this triggers:
BUG: sleeping function called from invalid context at
./include/linux/sched/mm.h:323
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 570
...
#1: ffffffffc2cd24f8 (amdgpu_pasid_idr_lock){+.+.}-{3:3},
at: amdgpu_pasid_alloc+0x24/0x210 [amdgpu]
...
kmem_cache_alloc_noprof+0x41d/0x780
radix_tree_node_alloc.constprop.0+0x56/0x3a0
idr_get_free+0x330/0x830
idr_alloc_u32+0x14a/0x2e0
idr_alloc_cyclic+0xd3/0x1d0
amdgpu_pasid_alloc+0x51/0x210 [amdgpu]
A mutex is not an option because amdgpu_pasid_free() is reachable from
dma-fence callbacks (amdgpu_pasid_free_cb) which may run in IRQ context.
Use idr_preload(GFP_KERNEL) before taking the spinlock to pre-allocate
radix-tree nodes, then pass GFP_NOWAIT inside the critical section so
the allocator draws from the preloaded pool and never sleeps. This is
the standard kernel pattern for IDR allocation under a spinlock.
Fixes: 14b81abe7bdc ("drm/amdgpu: prevent immediate PASID reuse case")
Cc: [email protected]
Signed-off-by: Mikhail Gavrilov <[email protected]>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
index d88523568b62..515775eab2ef 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
@@ -67,10 +67,12 @@ int amdgpu_pasid_alloc(unsigned int bits)
if (bits == 0)
return -EINVAL;
+ idr_preload(GFP_KERNEL);
It's better/simpler to replace amdgpu_pasid_idr with xarray.
Thanks,
Lijo
spin_lock(&amdgpu_pasid_idr_lock);
pasid = idr_alloc_cyclic(&amdgpu_pasid_idr, NULL, 1,
- 1U << bits, GFP_KERNEL);
+ 1U << bits, GFP_NOWAIT);
spin_unlock(&amdgpu_pasid_idr_lock);
+ idr_preload_end();
if (pasid >= 0)
trace_amdgpu_pasid_allocated(pasid);
