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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
