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e4772031d1
Update the expected result of the selftest as recursion of task local
storage syscall and helpers have been relaxed. Now that the percpu
counter is removed, task local storage helpers, bpf_task_storage_get()
and bpf_task_storage_delete() can now run on the same CPU at the same
time unless they cause deadlock.
Note that since there is no percpu counter preventing recursion in
task local storage helpers, bpf_trampoline now catches the recursion
of on_update as reported by recursion_misses.
on_enter: tp_btf/sys_enter
on_update: fentry/bpf_local_storage_update
Old behavior New behavior
____________ ____________
on_enter on_enter
bpf_task_storage_get(&map_a) bpf_task_storage_get(&map_a)
bpf_task_storage_trylock succeed bpf_local_storage_update(&map_a)
bpf_local_storage_update(&map_a)
on_update on_update
bpf_task_storage_get(&map_a) bpf_task_storage_get(&map_a)
bpf_task_storage_trylock fail on_update::misses++ (1)
return NULL create and return map_a::ptr
map_a::ptr += 1 (1)
bpf_task_storage_delete(&map_a)
return 0
bpf_task_storage_get(&map_b) bpf_task_storage_get(&map_b)
bpf_task_storage_trylock fail on_update::misses++ (2)
return NULL create and return map_b::ptr
map_b::ptr += 1 (1)
create and return map_a::ptr create and return map_a::ptr
map_a::ptr = 200 map_a::ptr = 200
bpf_task_storage_get(&map_b) bpf_task_storage_get(&map_b)
bpf_task_storage_trylock succeed lockless lookup succeed
bpf_local_storage_update(&map_b) return map_b::ptr
on_update
bpf_task_storage_get(&map_a)
bpf_task_storage_trylock fail
lockless lookup succeed
return map_a::ptr
map_a::ptr += 1 (201)
bpf_task_storage_delete(&map_a)
bpf_task_storage_trylock fail
return -EBUSY
nr_del_errs++ (1)
bpf_task_storage_get(&map_b)
bpf_task_storage_trylock fail
return NULL
create and return ptr
map_b::ptr = 100
Expected result:
map_a::ptr = 201 map_a::ptr = 200
map_b::ptr = 100 map_b::ptr = 1
nr_del_err = 1 nr_del_err = 0
on_update::recursion_misses = 0 on_update::recursion_misses = 2
On_enter::recursion_misses = 0 on_enter::recursion_misses = 0
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20260205222916.1788211-14-ameryhung@gmail.com
81 lines
1.6 KiB
C
81 lines
1.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2021 Facebook */
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#include "vmlinux.h"
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_tracing.h>
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#ifndef EBUSY
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#define EBUSY 16
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#endif
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char _license[] SEC("license") = "GPL";
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int nr_del_errs = 0;
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int test_pid = 0;
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struct {
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__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
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__uint(map_flags, BPF_F_NO_PREALLOC);
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__type(key, int);
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__type(value, long);
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} map_a SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
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__uint(map_flags, BPF_F_NO_PREALLOC);
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__type(key, int);
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__type(value, long);
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} map_b SEC(".maps");
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SEC("fentry/bpf_local_storage_update")
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int BPF_PROG(on_update)
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{
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struct task_struct *task = bpf_get_current_task_btf();
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long *ptr;
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if (!test_pid || task->pid != test_pid)
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return 0;
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/* This will succeed as there is no real deadlock */
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ptr = bpf_task_storage_get(&map_a, task, 0,
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BPF_LOCAL_STORAGE_GET_F_CREATE);
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if (ptr) {
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int err;
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*ptr += 1;
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err = bpf_task_storage_delete(&map_a, task);
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if (err == -EBUSY)
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nr_del_errs++;
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}
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/* This will succeed as there is no real deadlock */
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ptr = bpf_task_storage_get(&map_b, task, 0,
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BPF_LOCAL_STORAGE_GET_F_CREATE);
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if (ptr)
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*ptr += 1;
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return 0;
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}
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SEC("tp_btf/sys_enter")
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int BPF_PROG(on_enter, struct pt_regs *regs, long id)
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{
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struct task_struct *task;
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long *ptr;
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task = bpf_get_current_task_btf();
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if (!test_pid || task->pid != test_pid)
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return 0;
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ptr = bpf_task_storage_get(&map_a, task, 0,
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BPF_LOCAL_STORAGE_GET_F_CREATE);
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if (ptr && !*ptr)
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*ptr = 200;
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ptr = bpf_task_storage_get(&map_b, task, 0,
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BPF_LOCAL_STORAGE_GET_F_CREATE);
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if (ptr && !*ptr)
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*ptr = 100;
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return 0;
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}
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