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Re: [PATCH] Use CC atomic builtins if available [was: Re: TAS patch for building on armel/armhf thumb]

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: pgsql-bugs(at)postgresql(dot)org
Subject: Re: [PATCH] Use CC atomic builtins if available [was: Re: TAS patch for building on armel/armhf thumb]
Date: 2011-12-19 16:09:13
Message-ID: 4EEF61A9.1060608@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-bugs
On 19.12.2011 17:39, Martin Pitt wrote:
> Heikki Linnakangas [2011-12-19 17:09 +0200]:
>> One thing that caught my eye: if you use __sync_lock_and_test() to
>> implement S_LOCK(), you really should be using __sync_lock_release()
>> for S_UNLOCK().
>
> Right, the patch I send does that:
>
>   #define S_UNLOCK(lock) __sync_lock_release(lock)

Oh, I'm blind...

Can you comment on or test whether the existing TAS implementation is 
broken on ARM, because the existing S_UNLOCK() on ARM doesn't act as a 
memory barrier? If we're going to keep the existing snippet of inline 
assembly for those variants of ARM where it works, we need to either fix 
S_UNLOCK or convince ourselves that it's not broken.

I'll take a closer look at the same on Itanium.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com

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