Messages in this thread | | | Date | Mon, 19 Oct 2015 11:51:57 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC] perf: fix building for ARCv1 |
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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.
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