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Message-ID: <C2D7FE5348E1B147BCA15975FBA23075665B0A9F@IN01WEMBXB.internal.synopsys.com> Date: Mon, 3 Aug 2015 14:40:13 +0000 From: Vineet Gupta <Vineet.Gupta1@...opsys.com> To: Peter Zijlstra <peterz@...radead.org> CC: lkml <linux-kernel@...r.kernel.org>, "arc-linux-dev@...opsys.com" <arc-linux-dev@...opsys.com> Subject: Re: [PATCH 6/6] ARCv2: spinlock/rwlock: Reset retry delay when starting a new spin-wait cycle On Monday 03 August 2015 05:14 PM, Peter Zijlstra wrote: > On Mon, Aug 03, 2015 at 03:33:08PM +0530, Vineet Gupta wrote: >> > A spin lock could be available momentarily, but the SCOND to actually >> > acquire it might still fail due to concurrent update from other core(s). >> > To elide hardware lock, the sequence is retried after a "delay" which is >> > increased expoenntially to get a nice backoff behaviour. >> > >> > However, this could cause the delay counter to get to a high value. Thus >> > when the next spin cycle restarts, reset the counter back to starting >> > value of 1. > Cute.. fwiw, did you look at what Sparc64 does? > Can't really comprehend what's special there - are you referring to the special branching or to the out of line slow path code for 32 bit version. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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