From: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Date: Mon, 2 Mar 2015 19:19:14 +0000 (+0000)
Subject: arm64: Implement cpu_relax as yield
X-Git-Tag: omap-for-v4.2/o2_dc~115^2~37
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1baa82f48030f38d1895301f1ec93acbcb3d15db;p=pandora-kernel.git

arm64: Implement cpu_relax as yield

ARM64 has the yield nop hint which has the intended semantics of
cpu_relax. Implement.

The immediate application is ARM CPU emulators. An emulator can take
advantage of the yield hint to de-prioritise an emulated CPU in favor
of other emulation tasks. QEMU A64 SMP emulation has yield awareness,
and sees a significant boot time performance increase with this change.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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