Date: Thu, 14 Feb 2008 13:33:10 -0600
From: Corey Minyard <minyard@acm.org>
Subject: Re: [PATCH 3/4] IPMI: convert locked counters to atomics
In-reply-to: <20080214111143.7e0937ea.akpm@linux-foundation.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>,
       OpenIPMI Developers <openipmi-developer@lists.sourceforge.net>,
       Konstantin Baydarov <kbaidarov@ru.mvista.com>
Message-id: <47B49776.7000802@acm.org>
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References: <20080214183051.GC20148@minyard.local>
 <20080214111143.7e0937ea.akpm@linux-foundation.org>
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Andrew Morton wrote:
>> +	for (i = 0; i < IPMI_NUM_STATS; i++)
>> +		atomic_set(&intf->stats[i], 0);
>>     
>
> And this is why it would be very hard for any architecture to ever
> implement atomic_t as
>
> struct atomic_t {
> 	int counter;
> 	spinlock_t lock;
> };
>
> The interface assumes that atomic_set() fully initialises the atomic_t, and
> that atomic_set() can be used agaisnt both an uninitialised atomic_t and
> against an already-initialised atomic_t.  IOW, we don't have atomic_init().
>
> So would our hypothetical future architcture's atomic_set() do spin_lock(),
> or would it do spin_lock_init()?  Either one is wrong in many atomic_set
> callsites.
>
> Oh well.
>   
Yeah, I thought the same thing when I did this.  Do we start working
on an atomic_init()?  It would be easy enough to set it to atomic_set()
for current architectures.

-corey
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