Re: [PATCH 5/8] module: Add module_for_each_mod() function

[Petr Pavlu]

On 2/6/25 16:27, Steven Rostedt wrote:
> On Thu, 6 Feb 2025 14:28:17 +0900
> Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> wrote:
> 
>>> --- a/kernel/module/main.c
>>> +++ b/kernel/module/main.c
>>> @@ -3809,6 +3809,20 @@ bool is_module_text_address(unsigned long addr)
>>>  	return ret;
>>>  }
>>>    
>>
>> It is better to add a kerneldoc for this API.
> 
> Agreed, but I was planning on this changing. Waiting to hear from the
> module maintainers.
> 
>>
>> /** 
>>  * module_for_each_mod() - iterate all modules
>>  * @func: Callback function
>>  * @data: User data
>>  *
>>  * Call the @func with each module in the system. If @func returns !0, this
>>  * stops itrating. Note that @func must not sleep since it is called under
>>  * the preemption disabled.
>>  */
>>
>> BTW, do we really need to disable preempt or is it enough to call
>> rcu_read_lock()?
> 
> Bah, as I expected this function to be changed, I didn't spend too much
> time on looking at its implementation. I just cut and pasted how the other
> loops worked. But yes, it should not be disabling preemption. In fact, I
> think the module code itself should not be disabling preemption!
> 
> I'll have to go and look into that.

The series "module: Use RCU instead of RCU-sched" from Sebastian Andrzej
Siewior cleans this up [1]. It is currently queued on modules-next (for
6.15-rc1).

The new function module_for_each_mod() should then use "guard(rcu)();".

[1] https://lore.kernel.org/linux-modules/20250108090457.512198-1-bigeasy@xxxxxxxxxxxxx/

-- 
Thanks,
Petr

>>> +void module_for_each_mod(int(*func)(struct module *mod, void *data), void *data)
>>> +{
>>> +	struct module *mod;
>>> +
>>> +	preempt_disable();
>>> +	list_for_each_entry_rcu(mod, &modules, list) {
>>> +		if (mod->state == MODULE_STATE_UNFORMED)
>>> +			continue;
>>> +		if (func(mod, data))
>>> +			break;
>>> +	}
>>> +	preempt_enable();
>>> +}
>>> +
>>>  /**
>>>   * __module_text_address() - get the module whose code contains an address.
>>>   * @addr: the address.
>>> -- 
>