Re: [PATCH bpf-next v8 4/4] selftests/bpf: Add tests for bpf_rcu_read_lock()

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On 11/22/22 11:53 AM, Yonghong Song wrote:
+SEC("?fentry.s/" SYS_PREFIX "sys_nanosleep")
+int task_acquire(void *ctx)
+{
+	struct task_struct *task, *real_parent;
+
+	task = bpf_get_current_task_btf();
+	bpf_rcu_read_lock();
+	real_parent = task->real_parent;
+	/* acquire a reference which can be used outside rcu read lock region */
+	real_parent = bpf_task_acquire(real_parent);
Does the bpf_task_acquire() kfunc need a change to do refcount_inc_not_zero() and KF_RET_NULL?

Also, some more 'skip' checks in prog_tests/rcu_read_lock.c is needed for gcc. This is failing in gcc CI:

https://github.com/kernel-patches/bpf/actions/runs/3527747280/jobs/5917628248#step:6:5624

  ; bpf_rcu_read_lock();
  2: (85) call bpf_rcu_read_lock#26650
  ; real_parent = task->real_parent;
3: (79) r1 = *(u64 *)(r6 +1416) ; R1_w=ptr_task_struct(off=0,imm=0) R6_w=trusted_ptr_task_struct(off=0,imm=0)
  ; real_parent = bpf_task_acquire(real_parent);
  4: (85) call bpf_task_acquire#26666
  R1 must be referenced or trusted	
processed 5 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
  -- END PROG LOAD LOG --
  libbpf: prog 'task_acquire': failed to load: -22

+	bpf_rcu_read_unlock();
+	(void)bpf_task_storage_get(&map_a, real_parent, 0, 0);
+	bpf_task_release(real_parent);
+	return 0;
+}
+
+SEC("?fentry.s/" SYS_PREFIX "sys_nanosleep")
+int no_lock(void *ctx)
+{
+	struct task_struct *task, *real_parent;
+
+	/* no bpf_rcu_read_lock(), old code still works */
+	task = bpf_get_current_task_btf();
+	real_parent = task->real_parent;
+	bpf_printk("pid %u\n", real_parent->pid);

nit. Can bpf_printk be avoided here?

Others lgtm.




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