Re: [PATCH bpf-next 1/2] bpf: Mark tracing_multi trampolines as ftrace managed

[Leon Hwang]

On 2026/7/11 06:15, Jiri Olsa wrote:
> On Fri, Jul 10, 2026 at 10:47:33PM +0800, Leon Hwang wrote:
>> Since tracing_multi link does not set ftrace_managed, it would fail to
>> release the tracing_multi link when attaching tracing_multi link and
>> then attaching fentry link.
>>
>> [    3.714215] WARNING: kernel/bpf/trampoline.c:1727 at bpf_trampoline_multi_detach+0x20b/0x240, CPU#1: test_progs/97
>> ...
>> [    3.733170]  bpf_tracing_multi_link_release+0x14/0x30
>> [    3.733890]  bpf_link_free+0x58/0x130
>> [    3.734414]  bpf_link_release+0x23/0x30
>>
>> Fix it by setting 'ftrace_managed = true' in register_fentry_multi().
>>
>> Fixes: aef4dfa790b2 ("bpf: Add bpf_trampoline_multi_attach/detach functions")
>> Signed-off-by: Leon Hwang <leon.hwang@xxxxxxxxx>
>> ---
>>  kernel/bpf/trampoline.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
>> index 1a721fc4bef5..6eadf64f7ec9 100644
>> --- a/kernel/bpf/trampoline.c
>> +++ b/kernel/bpf/trampoline.c
>> @@ -1536,6 +1536,7 @@ static int register_fentry_multi(struct bpf_trampoline *tr, struct bpf_tramp_ima
>>  	if (bpf_trampoline_use_jmp(tr->flags))
>>  		addr = ftrace_jmp_set(addr);
>>  
>> +	tr->func.ftrace_managed = true;
> 
> I wonder we could set tr->func.ftrace_managed early in bpf_trampoline_get,
> but we could do that as follow up


Makes sense. Let me try it when adding tracing_multi link support for
bpf progs.

> 
> Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>


Thanks for your review.

Leon

> 
> thanks,
> jirka
> 
> 
>>  	ftrace_hash_add(data->reg, data->entry, ip, addr);
>>  	tr->cur_image = im;
>>  	return 0;
>> -- 
>> 2.55.0
>>