From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752311AbdIVSqS (ORCPT ); Fri, 22 Sep 2017 14:46:18 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:38470 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752071AbdIVSqO (ORCPT ); Fri, 22 Sep 2017 14:46:14 -0400 Date: Fri, 22 Sep 2017 11:46:10 -0700 From: "Paul E. McKenney" To: Sebastian Andrzej Siewior Cc: Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] srcu: queue work without holding the lock Reply-To: paulmck@linux.vnet.ibm.com References: <20170922152806.22860-1-bigeasy@linutronix.de> <20170922152806.22860-2-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170922152806.22860-2-bigeasy@linutronix.de> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17092218-0056-0000-0000-000003CD7A1A X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007779; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000231; SDB=6.00920830; UDB=6.00462737; IPR=6.00701051; BA=6.00005601; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00017249; XFM=3.00000015; UTC=2017-09-22 18:46:11 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17092218-0057-0000-0000-00000804801C Message-Id: <20170922184610.GT3521@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-09-22_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1707230000 definitions=main-1709220261 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 22, 2017 at 05:28:05PM +0200, Sebastian Andrzej Siewior wrote: > On RT we can't invoke queue_delayed_work() within an atomic section > (which is provided by raw_spin_lock_irqsave()). > srcu_reschedule() invokes queue_delayed_work() outside of the > raw_spin_lock_irq_rcu_node() section so this should be fine here, too. > If the remaining callers of call_srcu() aren't atomic > (spin_lock_irqsave() is fine) then this should work on RT, too. Just to make sure I understand... The problem is not the _irqsave, but rather the raw_? Thanx, Paul > Signed-off-by: Sebastian Andrzej Siewior > --- > kernel/rcu/srcutree.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c > index d190af0e56f8..3ee4ef40f23e 100644 > --- a/kernel/rcu/srcutree.c > +++ b/kernel/rcu/srcutree.c > @@ -648,12 +648,17 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, > /* If grace period not already done and none in progress, start it. */ > if (!rcu_seq_done(&sp->srcu_gp_seq, s) && > rcu_seq_state(sp->srcu_gp_seq) == SRCU_STATE_IDLE) { > + unsigned long delay; > + > WARN_ON_ONCE(ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)); > srcu_gp_start(sp); > + delay = srcu_get_delay(sp); > + raw_spin_unlock_irqrestore_rcu_node(sp, flags); > + > queue_delayed_work(system_power_efficient_wq, &sp->work, > - srcu_get_delay(sp)); > - } > - raw_spin_unlock_irqrestore_rcu_node(sp, flags); > + delay); > + } else > + raw_spin_unlock_irqrestore_rcu_node(sp, flags); > } > > /* > -- > 2.14.1 >