On 11/14/24 9:08 PM, Alexei Starovoitov wrote:
On Thu, Nov 14, 2024 at 7:53 PM Yonghong Song <yonghong.song@xxxxxxxxx> wrote:When running bpf selftest (./test_progs -j), the following warnings showed up: $ ./test_progs -t arena_atomics ... BUG: using smp_processor_id() in preemptible [00000000] code: kworker/u19:0/12501 caller is bpf_mem_free+0x128/0x330 ... Call Trace: <TASK> dump_stack_lvl check_preemption_disabled bpf_mem_free range_tree_destroy arena_map_free bpf_map_free_deferred process_scheduled_works ... For selftests arena_htab and arena_list, similar smp_process_id() BUGs are dumped, and the following are two stack trace: <TASK> dump_stack_lvl check_preemption_disabled bpf_mem_alloc range_tree_set arena_map_alloc map_create ... <TASK> dump_stack_lvl check_preemption_disabled bpf_mem_alloc range_tree_clear arena_vm_fault do_pte_missing handle_mm_fault do_user_addr_fault ... Adding migrate_{disable,enable}() around related arena_*() calls can fix the issue. Fixes: b795379757eb ("bpf: Introduce range_tree data structure and use it in bpf arena") Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx> --- kernel/bpf/arena.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c index 3e1dfe349ced..9a55d18032a4 100644 --- a/kernel/bpf/arena.c +++ b/kernel/bpf/arena.c @@ -134,7 +134,9 @@ static struct bpf_map *arena_map_alloc(union bpf_attr *attr) INIT_LIST_HEAD(&arena->vma_list); bpf_map_init_from_attr(&arena->map, attr); range_tree_init(&arena->rt); + migrate_disable(); range_tree_set(&arena->rt, 0, attr->max_entries); + migrate_enable(); mutex_init(&arena->lock); return &arena->map; @@ -185,7 +187,9 @@ static void arena_map_free(struct bpf_map *map) apply_to_existing_page_range(&init_mm, bpf_arena_get_kern_vm_start(arena), KERN_VM_SZ - GUARD_SZ, existing_page_cb, NULL); free_vm_area(arena->kern_vm); + migrate_disable(); range_tree_destroy(&arena->rt); + migrate_enable(); bpf_map_area_free(arena); } @@ -276,7 +280,9 @@ static vm_fault_t arena_vm_fault(struct vm_fault *vmf) /* User space requested to segfault when page is not allocated by bpf prog */ return VM_FAULT_SIGSEGV; + migrate_disable(); ret = range_tree_clear(&arena->rt, vmf->pgoff, 1); + migrate_enable();Thanks for the fix. I thought I had all debug configs enabled :( Could you please add migrate_disable/enable into range_tree.c around bpf_mem_alloc/free calls instead ? range_tree user shouldn't need to worry about this internal details.
Sure. Will send v2 shortly.
pw-bot: cr
