linux-kernel - Re: [PATCH 1/4] ipc/sem.c: convert undo structures to struct list

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Date:	Mon, 09 Jun 2008 08:56:06 +0200
From:	Nadia Derbey <Nadia.Derbey@...l.net>
To:	Manfred Spraul <manfred@...orfullife.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] ipc/sem.c: convert undo structures to struct list_head

Manfred Spraul wrote:
> Nadia Derbey wrote:
> 
>> Manfred Spraul wrote:
>>
>>> The undo structures contain two linked lists, the
>>> attached patch replaces them with generic struct list_head lists.
>>
>>
>> If I'm not wrong the undo list is a singly-linked list.
>> So here we are moving from a set of 4 pointers to a set of 8 pointers.
>> It's true that this makes the code much much more readable and clear, 
>> but I was wondering if it's worth?
>>
> IMHO yes: Everything is allocated on demand and memory is not that 
> expensive.
> 
> With regard to the asserts: I'm a big fan of asserts, I usually use them 
> to document the locking.

And you're completely right: when I see your new semaphore code, we can 
easily see what is the lock needed to protect a given field.

> Perhaps assert_spin_locked() should evalute to a nop() for 
> non-CONFIG_DEBUG builds?

Well, it's unconditionally defined as a BUG_ON(!spin_is_locked())

Regards,
Nadia




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