[fpc-devel] Re: freepascal support for debian armhf

[Paul Brook]

> > b) The SWP instruction is gone. It may fault, it may get fixed up by
> > the kernel (slowly), but it shouldn't be used anymore (it's not
> > compatible with mutli-core designs, Load/store exclusive should be
> > used instead).
> 
> swp is currently replaced with ldrex/strex in the run time library in
> you target ARMv6 or above.

For linux systems where you can't use ldrex unconditionally you should be 
using the __kuser_cmpxchg helper.  See linux 
Documentation/arm/kernel_user_helpers.txt

This should still give a fairly efficient implementation on later cores.

Paul