From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wj0-f197.google.com (mail-wj0-f197.google.com [209.85.210.197]) by kanga.kvack.org (Postfix) with ESMTP id E343B6B025E for ; Wed, 30 Nov 2016 02:02:19 -0500 (EST) Received: by mail-wj0-f197.google.com with SMTP id xy5so30686005wjc.0 for ; Tue, 29 Nov 2016 23:02:19 -0800 (PST) Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com. [148.163.158.5]) by mx.google.com with ESMTPS id tt4si62552683wjb.245.2016.11.29.23.02.18 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 29 Nov 2016 23:02:18 -0800 (PST) Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uAU6xIIR102587 for ; Wed, 30 Nov 2016 02:02:17 -0500 Received: from e38.co.us.ibm.com (e38.co.us.ibm.com [32.97.110.159]) by mx0b-001b2d01.pphosted.com with ESMTP id 271nqpv3nv-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 30 Nov 2016 02:02:17 -0500 Received: from localhost by e38.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 30 Nov 2016 00:02:15 -0700 Date: Tue, 29 Nov 2016 23:02:12 -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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Message-Id: <20161130070212.GM3924@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 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. > >> > >>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? 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