On Friday 05 February 2016 09:40 PM, acme at redhat.com wrote: > Em Fri, Feb 05, 2016 at 11:18:52AM +0000, Noam Camus escreveu: >> Well here for EZchip I also see the: >> undefined reference to `__sync_add_and_fetch_4' >> undefined reference to `__sync_sub_and_fetch_4' > > Yeah, because there is no: tools/arch/arc/include/asm/atomic.h, can't > you guys adapt arch/arc/include/asm/atomic.h to use in userspace? Sure - however we need to support 3 variants: LLSC, !LLSC, EZCHIP If needed, latter 2 could be done using a new atomic assist syscall I presume kernel Kconfig items are no go in this header so this diversity management needs to use toolchain defined macros e.g. __ezchip__ > > - Arnaldo > >> This is since at file tools/include/asm/atomic.h we use the generic implementation >> If for ARC I could use just like x86 my own header file then functions like: >> atomic_inc() >> atomic_dec_and_test() >> Are easy to implement and you may see an example for such atomic methods in my patch set for the new platform. >> >> You however wants to use some GCC flag -matomic which I assume somehow will implement the above __sync*. >> I can't find the implementation but if it uses LLSC then it won't work for me since I am not supporting LLSC. > >> So seem that either I have my own header at kernel or that I need to >> change the GCC implementation for __sync* to use my atomic >> instructions. I am personally tend to the x86 solution and not the >> generic one since changing GCC will require to have new compiler >> dependency.
