[fedora-arm] ARMv5 and atomic operations

[Andrew Haley]

On 04/23/2012 09:31 PM, Nicolas Pitre wrote:
> On Mon, 23 Apr 2012, Andrew Haley wrote:
> 
>> On 04/23/2012 06:36 PM, Thomas Meyer wrote:
>>> I'm running the Ubuntun 2.6.38 Tegra2 kernel (because of their fbdev
>>> support) on top of Fedora 17 armv5el on an Toshiba AC100 Laptop. The
>>> rsyslog package crashed everytime because of the missing kernel support
>>> of cmpxchg64. So when relying on the kernel helpers make sure that the
>>> resp. kernel support exists.
>>
>> Indeed.  I had to write a workaround in IcedTea (i.e. java) on ARM for
>> just this reason.  If you can't depend on a kernel helper being there I
>> can't see it's of any use.
> 
> Kernel helpers don't disappear with time.  You therefore can probe for 
> their availability (see the documentation) in case the kernel support 
> could be backported, or just refuse to run if the kernel version isn't 
> recent enough.  This is not much different from relying on a new 
> syscall.

Indeed it is.  What would I gain from adding such a test?  All I can
see is extra complication, untested code paths, and larger programs.
The untested code path is particularly nasty.

Andrew.