cvs commit: src/sys/kern uipc_mbuf.c

[John Baldwin]

On Mar 3, 2005, at 1:24 AM, Alan Cox wrote:

> On Thu, Mar 03, 2005 at 02:41:37AM +0000, Doug White wrote:
>> dwhite      2005-03-03 02:41:37 UTC
>>
>>   FreeBSD src repository
>>
>>   Modified files:
>>     sys/kern             uipc_mbuf.c
>>   Log:
>>   Insert volatile cast to discourage gcc from optimizing the read 
>> outside
>>   of the while loop.
>>
>>   Suggested by:   alc
>>   MFC after:      1 day
>>
>>   Revision  Changes    Path
>>   1.144     +4 -1      src/sys/kern/uipc_mbuf.c
>
> I tend to believe that the sparc64's casa() implementation is the real
> culprit here.  Specifically, I don't believe the right asm operand
> constraints are being used.  If I'm correct, the addition of volatile
> here is unnecessary.  Can we hold the MFC until this hypothesis is
> proven or disproven?

Yes, it looks like it isn't clobbering "memory" which atomic operations
on other architectures do.

-- 

John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org