Re: [PATCH v1 2/2] cleanup.h: Introduce DEFINE_INACTIVE_GUARD and activate_guard

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

On 2024-09-02 11:43, Peter Zijlstra wrote:
> On Wed, Aug 28, 2024 at 10:37:19AM -0400, Mathieu Desnoyers wrote:
>> To cover scenarios where the scope of the guard differs from the scope
>> of its activation, introduce DEFINE_INACTIVE_GUARD() and activate_guard().
>>
>> Here is an example use for a conditionally activated guard variable:
>>
>> void func(bool a)
>> {
>> 	DEFINE_INACTIVE_GUARD(preempt_notrace, myguard);
>>
>> 	[...]
>> 	if (a) {
>> 		might_sleep();
>> 		activate_guard(preempt_notrace, myguard)();
>> 	}
>> 	[ protected code ]
>> }
> 
> So... I more or less proposed this much earlier:
> 
>    https://lore.kernel.org/all/20230919131038.GC39346@noisy.programming.kicks-ass.net/T/#mb7b84212619ac743dfe4d2cc81decce451586b27
> 
> and Linus took objection to similar patterns. But perhaps my naming
> wasn't right.

Then you suggested something like a "guard_if()":

https://lore.kernel.org/lkml/20231120221524.GD8262@noisy.programming.kicks-ass.net/

which I find really odd because it requires to evaluate the same
condition twice within the function if it is used as guard_if
expression and needed as expression within the rest of the function
flow. I find the original patch with labels and gotos less ugly
than the guard_if().

Hence my proposal to optionally separate the definition from the activation,
which nicely integrates with the existing code flow.

If Linus' objections were mainly about naming, perhaps what I am
suggestion here may be more to his liking ?

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com