From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758779AbcIWCpT (ORCPT ); Thu, 22 Sep 2016 22:45:19 -0400 Received: from smtprelay0109.hostedemail.com ([216.40.44.109]:58273 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757383AbcIWCpS (ORCPT ); Thu, 22 Sep 2016 22:45:18 -0400 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Spam-Summary: 50,0,0,,d41d8cd98f00b204,rostedt@goodmis.org,:::::::::,RULES_HIT:41:355:379:541:599:800:960:967:973:988:989:1260:1263:1277:1311:1313:1314:1345:1359:1437:1515:1516:1518:1534:1541:1593:1594:1711:1730:1747:1777:1792:2393:2525:2553:2560:2563:2682:2685:2859:2895:2897:2933:2937:2939:2942:2945:2947:2951:2954:3022:3138:3139:3140:3141:3142:3352:3622:3865:3867:3868:3870:3872:3874:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:5007:6117:6261:7875:8599:8660:9025:9388:10004:10400:10848:10967:11026:11232:11320:11658:11914:12043:12438:12555:12740:12760:12776:13069:13148:13230:13311:13357:13439:14096:14097:14106:14180:14181:14659:14721:14764:14849:21060:21063:21080:30054:30090:30091,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:none,Custom_rules:0:0:0,LFtime:4,LUA_SUMMARY:none X-HE-Tag: wood07_682b5e21a2b63 X-Filterd-Recvd-Size: 1986 Date: Thu, 22 Sep 2016 22:45:14 -0400 From: Steven Rostedt To: Jisheng Zhang Cc: Thomas Gleixner , , LKML , LAK Subject: Re: [PATCH] clocksource/drivers/ti-32k: Prevent ftrace recursion Message-ID: <20160922224514.696ae61b@gandalf.local.home> In-Reply-To: <20160923100431.6cf2c88f@xhacker> References: <20160922075621.3725-1-jszhang@marvell.com> <20160923100431.6cf2c88f@xhacker> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 23 Sep 2016 10:04:31 +0800 Jisheng Zhang wrote: > Hi Thomas, > > On Thu, 22 Sep 2016 15:58:03 +0200 Thomas Gleixner wrote: > > > On Thu, 22 Sep 2016, Jisheng Zhang wrote: > > > > > Currently ti-32k can be used as a scheduler clock. We properly marked > > > omap_32k_read_sched_clock() as notrace but we then call another > > > function ti_32k_read_cycles() that _wasn't_ notrace. > > > > > > Having a traceable function in the sched_clock() path leads to a > > > recursion within ftrace and a kernel crash. > > > > Kernel crash? Doesn't ftrace core prevent recursion? > > a recent similar issue: > > http://www.spinics.net/lists/arm-kernel/msg533480.html Right. But Thomas brought up recursion detection. And I said that would be the fix, but now thinking about it, I've updated the recursion protection so that timer issues should not cause a crash. I'd like to know more, as this appears to be mostly arm related. -- Steve