On Fri, 6 May 2011, Ramana Radhakrishnan wrote: > On 6 May 2011 16:06, Ken Werner <ken.wer...@linaro.org> wrote: > > > > Currently the GCC ARM backend doesn't provide a pattern to inline 64bit > > __sync_* functions but the compiler emits __sync_*_8 function calls [1]. The > > libgcc does not provide these symbols via the usual thin wrapper around the > > kernel helper [2] because the ARM Linux __kernel_cmpxchg supports 32bit > > only. > > My understanding is that for ARMv7 the GCC backend could be enhanced to > > inline > > the __sync_* functions by using the LDREXD and STREXD instructions. But for > > ARMv5 we would still rely on a new kernel helper. > > It's a bit tricky with when you want to use the kernel helper for v5t, > so we've got to find a way of turning this on only with special knobs > and not by default and that's a bit tricky.
What is the problem with v5t? > Think new user space and old kernel and a jump into never-never land. The kernel helpers are "versioned". At 0xffff0ffc you can read the number of helpers currently available. If a program uses a new helper then when it is started this value can be verified to equal or exceed the expected value and bail out otherwise. Nicolas _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
