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Message-ID: <bfe05b54-9714-46bc-9b59-ad091897c62d@suse.com>
Date: Mon, 10 Feb 2025 14:04:35 +0100
From: Petr Pavlu <petr.pavlu@...e.com>
To: Steven Rostedt <rostedt@...dmis.org>,
"Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
Mark Rutland <mark.rutland@....com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Luis Chamberlain <mcgrof@...nel.org>, Sami Tolvanen
<samitolvanen@...gle.com>, Daniel Gomez <da.gomez@...sung.com>,
linux-modules@...r.kernel.org,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH 5/8] module: Add module_for_each_mod() function
On 2/6/25 16:27, Steven Rostedt wrote:
> On Thu, 6 Feb 2025 14:28:17 +0900
> Masami Hiramatsu (Google) <mhiramat@...nel.org> 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@linutronix.de/
--
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.
>>> --
>
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