> -----Original Message----- > From: Arnd Bergmann [mailto:arnd@xxxxxxxx] > Sent: Wednesday, March 30, 2011 8:40 PM > To: Thomas Gleixner > Cc: Guan Xuetao; Paul Mundt; linux-kernel@xxxxxxxxxxxxxxx; linux-arch@xxxxxxxxxxxxxxx > Subject: Re: [PATCH] unicore32 fix: remove arch-specific futex support > > On Wednesday 30 March 2011, Thomas Gleixner wrote: > > The problem is that you need cmpxchg in user space as well. > > > > ARM does this with some syscall magic for machines which do not have > > cmpxchg. > > Ah, right. I wonder how sh does it. > > I also remember that the original unicore32 ABI had support for a cmpxchg > system call, but that was removed with the move to the generic syscall > table. > > It is of course possible to add it back using the __NR_arch_specific_syscall > entry point. > > Arnd For cmpxchg, we have both system call and kuser_cmpxchg supports in old abi which are similar to arm. The performance of system call version is too poor, so it could be only used for test. Thanks & Regards Guan Xuetao -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
