Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755059AbdDLRki (ORCPT ); Wed, 12 Apr 2017 13:40:38 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:49867 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754249AbdDLRke (ORCPT ); Wed, 12 Apr 2017 13:40:34 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 04/40] srcu: Check for tardy grace-period activity in cleanup_srcu_struct() Date: Wed, 12 Apr 2017 10:39:49 -0700 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20170412174003.GA23207@linux.vnet.ibm.com> References: <20170412174003.GA23207@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17041217-0008-0000-0000-000001F244D3 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006924; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000208; SDB=6.00846604; UDB=6.00417608; IPR=6.00625041; BA=6.00005286; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00015023; XFM=3.00000013; UTC=2017-04-12 17:40:32 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17041217-0009-0000-0000-00003497122A Message-Id: <1492018825-25634-4-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-04-12_13:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=3 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1702020001 definitions=main-1704120145 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2321 Lines: 58 Users of SRCU are obliged to complete all grace-period activity before invoking cleanup_srcu_struct(). This means that all calls to either synchronize_srcu() or synchronize_srcu_expedited() must have returned, and all calls to call_srcu() must have returned, and the last call to call_srcu() must have been followed by a call to srcu_barrier(). Furthermore, the caller must have done something to prevent any further calls to synchronize_srcu(), synchronize_srcu_expedited(), and call_srcu(). Therefore, if there has ever been an invocation of call_srcu() on the srcu_struct in question, the sequence of events must be as follows: 1. Prevent any further calls to call_srcu(). 2. Wait for any pre-existing call_srcu() invocations to return. 3. Invoke srcu_barrier(). 4. It is now safe to invoke cleanup_srcu_struct(). On the other hand, if there has ever been a call to synchronize_srcu() or synchronize_srcu_expedited(), the sequence of events must be as follows: 1. Prevent any further calls to synchronize_srcu() or synchronize_srcu_expedited(). 2. Wait for any pre-existing synchronize_srcu() or synchronize_srcu_expedited() invocations to return. 3. It is now safe to invoke cleanup_srcu_struct(). If there have been calls to all both types of functions (call_srcu() and either of synchronize_srcu() and synchronize_srcu_expedited()), then the caller must do the first three steps of the call_srcu() procedure above and the first two steps of the synchronize_s*() procedure above, and only then invoke cleanup_srcu_struct(). Reported-by: Paolo Bonzini Signed-off-by: Paul E. McKenney --- kernel/rcu/srcu.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c index ba41a5d04b49..6beeba7b0b67 100644 --- a/kernel/rcu/srcu.c +++ b/kernel/rcu/srcu.c @@ -261,6 +261,11 @@ void cleanup_srcu_struct(struct srcu_struct *sp) { if (WARN_ON(srcu_readers_active(sp))) return; /* Leakage unless caller handles error. */ + if (WARN_ON(!rcu_all_batches_empty(sp))) + return; /* Leakage unless caller handles error. */ + flush_delayed_work(&sp->work); + if (WARN_ON(sp->running)) + return; /* Caller forgot to stop doing call_srcu()? */ free_percpu(sp->per_cpu_ref); sp->per_cpu_ref = NULL; } -- 2.5.2