From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Fri, 18 Dec 2015 12:29:15 +0100 (CET) Received: from bombadil.infradead.org ([198.137.202.9]:37136 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S27007139AbbLRL3OXEkoe (ORCPT ); Fri, 18 Dec 2015 12:29:14 +0100 Received: from j217066.upc-j.chello.nl ([24.132.217.66] helo=twins) by bombadil.infradead.org with esmtpsa (Exim 4.80.1 #2 (Red Hat Linux)) id 1a9tDd-0003KD-2n; Fri, 18 Dec 2015 11:29:05 +0000 Received: by twins (Postfix, from userid 1000) id 341E11257A0D8; Fri, 18 Dec 2015 12:29:02 +0100 (CET) Date: Fri, 18 Dec 2015 12:29:02 +0100 From: Peter Zijlstra To: Daniel Thompson Cc: Jiri Kosina , Russell King - ARM Linux , Andrew Morton , Petr Mladek , Geert Uytterhoeven , Steven Rostedt , Ingo Molnar , Thomas Gleixner , "linux-kernel@vger.kernel.org" , the arch/x86 maintainers , "linux-arm-kernel@lists.infradead.org" , "adi-buildroot-devel@lists.sourceforge.net" , Cris , Linux MIPS Mailing List , "linuxppc-dev@lists.ozlabs.org" , linux-s390 , Linux-sh list , sparclinux Subject: Re: [PATCH v3 4/4] printk/nmi: Increase the size of NMI buffer and make it configurable Message-ID: <20151218112902.GO6344@twins.programming.kicks-ass.net> References: <1449667265-17525-1-git-send-email-pmladek@suse.com> <1449667265-17525-5-git-send-email-pmladek@suse.com> <20151211124159.GB3729@pathway.suse.cz> <20151211145725.b0e81bb4bb18fcd72ef5f557@linux-foundation.org> <20151211232113.GZ8644@n2100.arm.linux.org.uk> <5673DD60.7080302@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5673DD60.7080302@linaro.org> User-Agent: Mutt/1.5.21 (2012-12-30) Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 50683 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: peterz@infradead.org Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips On Fri, Dec 18, 2015 at 10:18:08AM +0000, Daniel Thompson wrote: > I'm not entirely sure that this is an improvement. What I do these days is delete everything in vprintk_emit() and simply call early_printk(). Kill the useless kmsg buffer crap and locking, just pound bytes to the UART registers without anything in between. The other semi usable solution is redirecting to trace_printk() and recovering the trace buffers from your kdump. But I've found that typically kdump doesn't work anymore if you properly wedge the machine. So this is very much a second rate solution. But this globally locked buffer, calling out to console drivers that do locking and even scheduling, is an unreliable unfixable trainwreck that I've given up on. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Date: Fri, 18 Dec 2015 11:29:02 +0000 Subject: Re: [PATCH v3 4/4] printk/nmi: Increase the size of NMI buffer and make it configurable Message-Id: <20151218112902.GO6344@twins.programming.kicks-ass.net> List-Id: References: <1449667265-17525-1-git-send-email-pmladek@suse.com> <1449667265-17525-5-git-send-email-pmladek@suse.com> <20151211124159.GB3729@pathway.suse.cz> <20151211145725.b0e81bb4bb18fcd72ef5f557@linux-foundation.org> <20151211232113.GZ8644@n2100.arm.linux.org.uk> <5673DD60.7080302@linaro.org> In-Reply-To: <5673DD60.7080302@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org On Fri, Dec 18, 2015 at 10:18:08AM +0000, Daniel Thompson wrote: > I'm not entirely sure that this is an improvement. What I do these days is delete everything in vprintk_emit() and simply call early_printk(). Kill the useless kmsg buffer crap and locking, just pound bytes to the UART registers without anything in between. The other semi usable solution is redirecting to trace_printk() and recovering the trace buffers from your kdump. But I've found that typically kdump doesn't work anymore if you properly wedge the machine. So this is very much a second rate solution. But this globally locked buffer, calling out to console drivers that do locking and even scheduling, is an unreliable unfixable trainwreck that I've given up on. From mboxrd@z Thu Jan 1 00:00:00 1970 From: peterz@infradead.org (Peter Zijlstra) Date: Fri, 18 Dec 2015 12:29:02 +0100 Subject: [PATCH v3 4/4] printk/nmi: Increase the size of NMI buffer and make it configurable In-Reply-To: <5673DD60.7080302@linaro.org> References: <1449667265-17525-1-git-send-email-pmladek@suse.com> <1449667265-17525-5-git-send-email-pmladek@suse.com> <20151211124159.GB3729@pathway.suse.cz> <20151211145725.b0e81bb4bb18fcd72ef5f557@linux-foundation.org> <20151211232113.GZ8644@n2100.arm.linux.org.uk> <5673DD60.7080302@linaro.org> Message-ID: <20151218112902.GO6344@twins.programming.kicks-ass.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Dec 18, 2015 at 10:18:08AM +0000, Daniel Thompson wrote: > I'm not entirely sure that this is an improvement. What I do these days is delete everything in vprintk_emit() and simply call early_printk(). Kill the useless kmsg buffer crap and locking, just pound bytes to the UART registers without anything in between. The other semi usable solution is redirecting to trace_printk() and recovering the trace buffers from your kdump. But I've found that typically kdump doesn't work anymore if you properly wedge the machine. So this is very much a second rate solution. But this globally locked buffer, calling out to console drivers that do locking and even scheduling, is an unreliable unfixable trainwreck that I've given up on.