Re: [PATCH-v2] ARC: syscall for userspace cmpxchg assist

2016-11-04 Thread Vineet Gupta
On 10/24/2016 09:17 AM, Vineet Gupta wrote: > Older ARC700 cores (ARC750 specifically) lack instructions to implement > atomic r-w-w. This is problematic for userspace libraries such as NPTL > which need atomic primitives. So enable them by providing kernel assist. > This is costly but really the o

[PATCH-v2] ARC: syscall for userspace cmpxchg assist

2016-10-24 Thread Vineet Gupta
Older ARC700 cores (ARC750 specifically) lack instructions to implement atomic r-w-w. This is problematic for userspace libraries such as NPTL which need atomic primitives. So enable them by providing kernel assist. This is costly but really the only sane soluton (othern than tight spinning using t