linux-kernel - Re: [PATCH 1/4] [RFC] net: Explicitly initialize u64_stats

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Message-ID: <52448C46.2050107@linaro.org>
Date:	Thu, 26 Sep 2013 12:34:30 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Mirko Lindner <mlindner@...vell.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Roger Luethi <rl@...lgate.ch>,
	Patrick McHardy <kaber@...sh.net>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Wensong Zhang <wensong@...ux-vs.org>,
	Simon Horman <horms@...ge.net.au>,
	Julian Anastasov <ja@....bg>, Jesse Gross <jesse@...ira.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org
Subject: Re: [PATCH 1/4] [RFC] net: Explicitly initialize u64_stats_sync structures
 for lockdep

On 09/26/2013 12:26 PM, Eric Dumazet wrote:
> On Thu, 2013-09-26 at 11:34 -0700, John Stultz wrote:
>> In order to enable lockdep on seqcount/seqlock structures, we
>> must explicitly initialize any locks.
>>
>> diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h
>> index 8da8c4e..c450e11 100644
>> --- a/include/linux/u64_stats_sync.h
>> +++ b/include/linux/u64_stats_sync.h
>> @@ -67,6 +67,13 @@ struct u64_stats_sync {
>>  #endif
>>  };
>>  
>> +
>> +#if BITS_PER_LONG == 32 && defined(CONFIG_SMP)
>> +#define u64_stats_init(syncp)	seqcount_init(syncp.seq)
>> +#else
>> +#define u64_stats_init(syncp)
>> +#endif
>> +
> I would prefer a function.
>
> static inline void u64_stats_init(struct u64_stats_sync *syncp)
> {
> #if BITS_PER_LONG == 32 && defined(CONFIG_SMP)
> 	seqcount_init(&syncp->seq);
> #endif
> }

No objection, though I worry that will obscure the lockdep key name,
causing all the u64_stat_sync locks to appear the same.

I'll give it a quick shot to see if the compiler inlines it well enough
to preserve the name.

thanks
-john

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