From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id 038066B0038 for ; Wed, 30 Nov 2016 07:05:06 -0500 (EST) Received: by mail-pg0-f70.google.com with SMTP id e9so19005884pgc.5 for ; Wed, 30 Nov 2016 04:05:05 -0800 (PST) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id c9si64038465pgf.116.2016.11.30.04.05.05 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 30 Nov 2016 04:05:05 -0800 (PST) Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uAUC4vQQ060710 for ; Wed, 30 Nov 2016 07:05:04 -0500 Received: from e33.co.us.ibm.com (e33.co.us.ibm.com [32.97.110.151]) by mx0a-001b2d01.pphosted.com with ESMTP id 271u9eafqr-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 30 Nov 2016 07:04:59 -0500 Received: from localhost by e33.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 30 Nov 2016 05:03:36 -0700 Date: Wed, 30 Nov 2016 04:03:33 -0800 From: "Paul E. McKenney" Subject: Re: next: Commit 'mm: Prevent __alloc_pages_nodemask() RCU CPU stall ...' causing hang on sparc32 qemu Reply-To: paulmck@linux.vnet.ibm.com References: <20161129212308.GA12447@roeck-us.net> <20161130012817.GH3924@linux.vnet.ibm.com> <20161130070212.GM3924@linux.vnet.ibm.com> <929f6b29-461a-6e94-fcfd-710c3da789e9@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <929f6b29-461a-6e94-fcfd-710c3da789e9@roeck-us.net> Message-Id: <20161130120333.GQ3924@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Guenter Roeck Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , sparclinux@vger.kernel.org, davem@davemloft.net On Wed, Nov 30, 2016 at 02:52:11AM -0800, Guenter Roeck wrote: > On 11/29/2016 11:02 PM, Paul E. McKenney wrote: > >On Tue, Nov 29, 2016 at 08:32:51PM -0800, Guenter Roeck wrote: > >>On 11/29/2016 05:28 PM, Paul E. McKenney wrote: > >>>On Tue, Nov 29, 2016 at 01:23:08PM -0800, Guenter Roeck wrote: > >>>>Hi Paul, > >>>> > >>>>most of my qemu tests for sparc32 targets started to fail in next-20161129. > >>>>The problem is only seen in SMP builds; non-SMP builds are fine. > >>>>Bisect points to commit 2d66cccd73436 ("mm: Prevent __alloc_pages_nodemask() > >>>>RCU CPU stall warnings"); reverting that commit fixes the problem. And I have dropped this patch. Michal Hocko showed me the error of my ways with this patch. Thanx, Paul > >>>>Test scripts are available at: > >>>> https://github.com/groeck/linux-build-test/tree/master/rootfs/sparc > >>>>Test results are at: > >>>> https://github.com/groeck/linux-build-test/tree/master/rootfs/sparc > >>>> > >>>>Bisect log is attached. > >>>> > >>>>Please let me know if there is anything I can do to help tracking down the > >>>>problem. > >>> > >>>Apologies!!! Does the patch below help? > >>> > >>No, sorry, it doesn't make a difference. > > > >Interesting... Could you please send me the build failure messages? > > > > There is no failure message; it just hangs until I abort the qemu session. > > http://kerneltests.org/builders/qemu-sparc-next/builds/532/steps/qemubuildcommand/logs/stdio > > Guenter > > > Thanx, Paul > > > >>Guenter > >> > >>> Thanx, Paul > >>> > >>>------------------------------------------------------------------------ > >>> > >>>commit 97708e737e2a55fed4bdbc005bf05ea909df6b73 > >>>Author: Paul E. McKenney > >>>Date: Tue Nov 29 11:06:05 2016 -0800 > >>> > >>> rcu: Allow boot-time use of cond_resched_rcu_qs() > >>> > >>> The cond_resched_rcu_qs() macro is used to force RCU quiescent states into > >>> long-running in-kernel loops. However, some of these loops can execute > >>> during early boot when interrupts are disabled, and during which time > >>> it is therefore illegal to enter the scheduler. This commit therefore > >>> makes cond_resched_rcu_qs() be a no-op during early boot. > >>> > >>> Signed-off-by: Paul E. McKenney > >>> > >>>diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h > >>>index 525ca34603b7..b6944cc19a07 100644 > >>>--- a/include/linux/rcupdate.h > >>>+++ b/include/linux/rcupdate.h > >>>@@ -423,7 +423,7 @@ extern struct srcu_struct tasks_rcu_exit_srcu; > >>> */ > >>>#define cond_resched_rcu_qs() \ > >>>do { \ > >>>- if (!cond_resched()) \ > >>>+ if (!is_idle_task(current) && !cond_resched()) \ > >>> rcu_note_voluntary_context_switch(current); \ > >>>} while (0) > >>> > >>>diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h > >>>index 7232d199a81c..20f5990deeee 100644 > >>>--- a/include/linux/rcutiny.h > >>>+++ b/include/linux/rcutiny.h > >>>@@ -228,6 +228,7 @@ static inline void exit_rcu(void) > >>>extern int rcu_scheduler_active __read_mostly; > >>>void rcu_scheduler_starting(void); > >>>#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ > >>>+#define rcu_scheduler_active false > >>>static inline void rcu_scheduler_starting(void) > >>>{ > >>>} > >>> > >>> > >> > > > > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org