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

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Message-ID: <472E383E.7080004@cosmosbay.com>
Date:	Sun, 04 Nov 2007 22:23:10 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Jarek Poplawski <jarkao2@...pl>
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

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.


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