Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
Pre-existing issues: - [High] The patch misses applying force=true to the error unwind path of kfd_process_alloc_gpuvm(), which can permanently leak internal BOs on unmap failure. - [High] Interruptible lock waiting in reserve_bo_and_cond_vms causes early return on pending signals, bypassing the forced free and silently leaking the BO. -- --- Patch [1]: [PATCH] drm/amdkfd: don't leak BOs when process teardown can't unmap them --- commit 01e590b61624d149d5da9ac22540c56bed4f9a55 Author: Bocaj Gnuoy <[email protected]> Subject: drm/amdkfd: don't leak BOs when process teardown can't unmap them This commit addresses a memory leak and subsequent TTM eviction deadlock that occurs when a process runs out of memory during teardown. It adds a force flag to amdgpu_amdkfd_gpuvm_free_memory_of_gpu() to ensure BOs are freed even if unmapping fails. The early -EBUSY return is retained for ioctl paths where userspace can retry. Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/5672 > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c > b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c > index 1e71829e0fc6b..dc1fa664fecac 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c > [ ... ] > @@ -1922,9 +1922,26 @@ int amdgpu_amdkfd_gpuvm_free_memory_of_gpu( > */ > > if (mapped_to_gpu_memory > 0) { > - pr_debug("BO VA 0x%llx size 0x%lx is still mapped.\n", > - mem->va, bo_size); > - return -EBUSY; > + /* > + * Refusing to free a mapped BO is only meaningful while the > + * process can still unmap it. On process teardown (@force) > + * there is no such chance: the caller drops the last handle > + * to @mem regardless, so bailing out here leaks the BO onto > + * process_info->kfd_bo_list / userptr_inval_list. Those lists > + * are then destroyed non-empty in > + * amdgpu_amdkfd_gpuvm_destroy_cb(), leaving a BO in TTM's > + * eviction LRU whose bo_vas point into the freed amdgpu_vm. > + * The next client to trigger eviction deadlocks in > + * amdgpu_vm_bo_move(). Tear the mappings down instead - the > + * VM is going away right after us anyway. > + */ > + if (!force) { > + pr_debug("BO VA 0x%llx size 0x%lx is still mapped.\n", > + mem->va, bo_size); > + return -EBUSY; > + } > + pr_warn("Force-freeing BO VA 0x%llx size 0x%lx still mapped %u > time(s)\n", > + mem->va, bo_size, mapped_to_gpu_memory); > } > > /* At this point the BO is guaranteed to be freed, so unpin the [Severity: High] This is a pre-existing issue, but can amdgpu_amdkfd_gpuvm_free_memory_of_gpu() still silently leak the BO if a signal interrupts the lock wait? Later in this function, the BO is removed from the tracking list before an interruptible lock wait is performed: amdgpu_amdkfd_gpuvm_free_memory_of_gpu() mutex_lock(&process_info->lock); if (!list_empty(&mem->validate_list)) list_del_init(&mem->validate_list); mutex_unlock(&process_info->lock); ret = reserve_bo_and_cond_vms(mem, NULL, BO_VM_ALL, &ctx); if (unlikely(ret)) return ret; If reserve_bo_and_cond_vms() returns early (e.g., -ERESTARTSYS) due to a pending signal, the function bails out. Because the BO was already removed from validate_list, it is left orphaned. Additionally, looking at the related caller kfd_process_free_gpuvm_map(), the map pointer is cleared before the free is attempted: kfd_process_free_gpuvm_map() if (map && !iosys_map_is_null(map)) { amdgpu_amdkfd_gpuvm_unmap_bo_from_kernel(mem); iosys_map_clear(map); } If the free is aborted by a signal, subsequent teardown passes will skip this map and ignore this BO. Does this sequence also create a risk of a silent memory leak and TTM eviction deadlock when userspace triggers an error and receives a concurrent signal? > [ ... ] > diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c > b/drivers/gpu/drm/amd/amdkfd/kfd_process.c > index 0a7c1900da959..6d5126aa6fe74 100644 > --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c > +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c > [ ... ] > @@ -814,7 +814,7 @@ static int kfd_process_alloc_gpuvm(struct > kfd_process_device *pdd, > > err_map_mem: > amdgpu_amdkfd_gpuvm_free_memory_of_gpu(kdev->adev, *mem, pdd->drm_priv, > - NULL); > + NULL, false); > err_alloc_mem: > *mem = NULL; > *kptr = NULL; [Severity: High] This is a pre-existing issue, but should the error unwind path in kfd_process_alloc_gpuvm() use force = true? When kfd_process_alloc_gpuvm() hits an error and jumps to err_map_mem, it calls amdgpu_amdkfd_gpuvm_free_memory_of_gpu() with force = false. It then immediately zeroes out the *mem pointer. If the free fails (for instance, an unmap failure under memory exhaustion where force = false causes an -EBUSY return), this BO appears to be permanently leaked since *mem is cleared and no later retry is possible. Could this lead to the same unrecoverable TTM eviction deadlock that this patch is fixing? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
