From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3zPxrB60TczF0X1 for ; Mon, 22 Jan 2018 14:34:34 +1100 (AEDT) In-Reply-To: <20180117124722.31063-1-npiggin@gmail.com> To: Nicholas Piggin , linuxppc-dev@lists.ozlabs.org From: Michael Ellerman Cc: Nicholas Piggin Subject: Re: powerpc/watchdog: remove arch_trigger_cpumask_backtrace Message-Id: <3zPxr81Gk4z9t39@ozlabs.org> Date: Mon, 22 Jan 2018 14:34:30 +1100 (AEDT) List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2018-01-17 at 12:47:22 UTC, Nicholas Piggin wrote: > The powerpc NMI IPIs may not be recoverable if they are taken in > some sections of code, and also there have been and still are issues > with taking NMIs (in KVM guest code, in firmware, etc) which makes them > a bit dangerous to use. > > Generic code like softlockup detector and rcu stall detectors really > hammer on trigger_*_backtrace, which has lead to further problems > because we've implemented it with the NMI. > > So stop providing NMI backtraces for now. Importantly, the powerpc code > uses NMI IPIs in crash/debug, and the SMP hardlockup watchdog. So if the > softlockup and rcu hang detection traces are not being printed because > the CPU is stuck with interrupts off, then the hard lockup watchdog > should get it with the NMI IPI. > > Fixes: 2104180a5369 ("powerpc/64s: implement arch-specific hardlockup watchdog") > Signed-of-by: Nicholas Piggin Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/47712a921bb781caf69fca9eae43be cheers