Messages in this thread | | | From | Vineet Gupta <> | Subject | Re: [RFC] perf: fix building for ARCv1 | Date | Mon, 19 Oct 2015 10:04:29 +0000 |
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On Monday 19 October 2015 03:22 PM, Peter Zijlstra wrote: > On Mon, Oct 19, 2015 at 09:46:35AM +0000, Vineet Gupta wrote: >> > On ARC we could use the atomic EXchange to implement a user space only binary >> > semaphore - these atomic ops will be small duration so it is OK to spin wait for a >> > little bit. That's how the old pthread library worked for ARC w/o any atomic support. > That has the obvious problem of lock-holder-preemption and the horrible > performance issues that result from that. > > I think the syscall at least has deterministic behaviour, whereas that > userspace spin loop has this abysmal worst case thing.
I agree - we can add that syscall trivially and use it based on build time feature detection for atomics !
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