linux-kernel - Re: [PATCH v2 4/5] locking/lockdep: Make class->ops a percpu counter

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Message-ID: <62801eb9-16f2-606f-d3a2-61fef5b0a704@redhat.com>
Date:   Wed, 3 Oct 2018 09:57:24 -0400
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/5] locking/lockdep: Make class->ops a percpu counter

On 10/03/2018 03:48 AM, Peter Zijlstra wrote:
> On Tue, Oct 02, 2018 at 04:19:19PM -0400, Waiman Long wrote:
>> +DEFINE_PER_CPU(unsigned long [MAX_LOCKDEP_KEYS], lock_class_ops);
>> @@ -179,9 +181,30 @@ DECLARE_PER_CPU(struct lockdep_stats, lockdep_stats);
>>  	}								\
>>  	__total;							\
>>  })
>> +
>> +static inline void debug_class_ops_inc(struct lock_class *class)
>> +{
>> +	int idx;
>> +
>> +	idx = class - lock_classes;
>> +	__this_cpu_inc(lock_class_ops[idx]);
>> +}
>> +
>> +static inline unsigned long debug_class_ops_read(struct lock_class *class)
>> +{
>> +	int idx, cpu;
>> +	unsigned long ops = 0;
>> +
>> +	idx = class - lock_classes;
>> +	for_each_possible_cpu(cpu)
>> +		ops += per_cpu(lock_class_ops[idx], cpu);
>> +	return ops;
>> +}
> Would it make sense to stick that in struct lockdep_stats ?
>
> A little something like:
>
> struct lockdep_stats {
> 	/* ... */
> 	int	lock_class_ops[MAX_LOCKDEP_KEYS];
> };
>
> and then use:
>
> 	debug_atomic_inc(lock_class_ops[idx]);
>
Yes, I can certainly do that. Thanks for pointing this out. Will post an
updated patch just for this one.

Cheers,
Longman