From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mailout1.w2.samsung.com ([211.189.100.11]:59085 "EHLO usmailout1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756527AbcAJAXx (ORCPT ); Sat, 9 Jan 2016 19:23:53 -0500 Received: from uscpsbgex1.samsung.com (u122.gpu85.samsung.co.kr [203.254.195.122]) by mailout1.w2.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0O0P00ENDNB2YO60@mailout1.w2.samsung.com> for linux-watchdog@vger.kernel.org; Sat, 09 Jan 2016 19:13:50 -0500 (EST) Subject: arm/arm64 HARDLOCKUP Detector and PERF NMI support References: <569199C0.9030500@samsung.com> To: "linux-arm-kernel@lists.infradead.org" , mark.rutland@arm.com, Will Deacon , Marc Zyngier , Catalin Marinas , Russell King - ARM Linux From: Mario Smarduch Cc: wim@iguana.be, Christoffer Dall , linux-watchdog@vger.kernel.org Message-id: <5691A23C.8060807@samsung.com> Date: Sat, 09 Jan 2016 16:13:48 -0800 MIME-version: 1.0 In-reply-to: <569199C0.9030500@samsung.com> Content-type: text/plain; charset=utf-8 Content-transfer-encoding: 7bit Sender: linux-watchdog-owner@vger.kernel.org List-Id: linux-watchdog@vger.kernel.org I'm trying to get HARDLOCKUP detector to work on arm (on foundation model and Juno, but armv7 should have the same issue). Turns out there is no PERF NMI support (HAVE_PERF_EVENTS_NMI), which I guess would be PMU NMI - I tested overflow on cycle counter and PMU interrupts can be masked. HARDLOCKUP assumes perf interrupts are non-maskable and uses the PMU to program an NMI to detect hard lockup and that in turn drives softlockup detection. Is there something, someplace in ARM manuals that addresses this, searched the manuals but couldn't find anything? Or other approaches that I'm not aware off or have floated on the mailing list. It's a pretty important feature for some environments. - Mario