netdev - Re: [PATCH] INET : removes per bucket rwlock in tcp/dccp ehash table

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Date:	Mon, 05 Nov 2007 00:08:30 +0100
From:	Jarek Poplawski <jarkao2@...pl>
To:	Eric Dumazet <dada1@...mosbay.com>
CC:	David Miller <davem@...emloft.net>, ak@...e.de,
	netdev@...r.kernel.org, acme@...hat.com
Subject: Re: [PATCH] INET : removes per bucket rwlock in tcp/dccp ehash table

Eric Dumazet wrote, On 11/04/2007 10:23 PM:

> Jarek Poplawski a écrit :
>> Jarek Poplawski wrote, On 11/04/2007 06:58 PM:
>>
>>> Eric Dumazet wrote, On 11/04/2007 12:31 PM:
>> ...
>>
>>>> +static inline int inet_ehash_locks_alloc(struct inet_hashinfo *hashinfo)
>>>> +{
>> ...
>>
>>>> +	if (sizeof(rwlock_t) != 0) {
>> ...
>>
>>>> +		for (i = 0; i < size; i++)
>>>> +			rwlock_init(&hashinfo->ehash_locks[i]);
>>> This looks better now, but still is doubtful to me: even if it's safe with
>>> current rwlock implementation, can't we imagine some new debugging or
>>> statistical code added, which would be called from rwlock_init() without
>>> using rwlock_t structure? IMHO, if read_lock() etc. are called in such a
>>> case, rwlock_init() should be done as well.
>>
>> Of course I mean: if sizeof(rwlock_t) == 0.
> 
> Given those two choices :
> 
> #if defined(CONFIG_SMP) || defined(CONFIG_PROVE__LOCKING)
>      kmalloc(sizeof(rwlock_t) * size);
> #endif
> 
> and
> 
>     if (sizeof(rwlock_t) != 0) {
>         kmalloc(sizeof(rwlock_t) * size);
>     }
> 
> I prefer the 2nd one. Less error prone, and no need to remember how are 
> spelled the gazillions CONFIG_something we have.


I've written it's better, too. But this could be improved yet (someday),
I hope.

Thanks,
Jarek P.
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