From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752212AbeBTX0p (ORCPT ); Tue, 20 Feb 2018 18:26:45 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:44972 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751925AbeBTXZE (ORCPT ); Tue, 20 Feb 2018 18:25:04 -0500 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Cc: mingo@kernel.org, stern@rowland.harvard.edu, parri.andrea@gmail.com, will.deacon@arm.com, peterz@infradead.org, boqun.feng@gmail.com, npiggin@gmail.com, dhowells@redhat.com, j.alglave@ucl.ac.uk, luc.maranget@inria.fr, akiyks@gmail.com, nborisov@suse.com, "Paul E. McKenney" Subject: [PATCH RFC tools/lkmm 10/12] tools/memory-model: Add a S lock-based external-view litmus test Date: Tue, 20 Feb 2018 15:25:10 -0800 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20180220232405.GA19274@linux.vnet.ibm.com> References: <20180220232405.GA19274@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18022023-0044-0000-0000-000003E72FDE X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008566; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000254; SDB=6.00992685; UDB=6.00504342; IPR=6.00772031; MB=3.00019661; MTD=3.00000008; XFM=3.00000015; UTC=2018-02-20 23:25:02 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18022023-0045-0000-0000-00000817350B Message-Id: <1519169112-20593-10-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-02-20_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1802200276 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Alan Stern This commit adds a litmus test in which P0() and P1() form a lock-based S litmus test, with the addition of P2(), which observes P0()'s and P1()'s accesses with a full memory barrier but without the lock. This litmus test asks whether writes carried out by two different processes under the same lock will be seen in order by a third process not holding that lock. The answer to this question is "yes" for all architectures supporting the Linux kernel, but is "no" according to the current version of LKMM. A patch to LKMM is under development. Signed-off-by: Alan Stern Signed-off-by: Paul E. McKenney --- .../ISA2+pooncelock+pooncelock+pombonce.litmus | 41 ++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus diff --git a/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus b/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus new file mode 100644 index 000000000000..7a39a0aaa976 --- /dev/null +++ b/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus @@ -0,0 +1,41 @@ +C ISA2+pooncelock+pooncelock+pombonce.litmus + +(* + * Result: Sometimes + * + * This test shows that the ordering provided by a lock-protected S + * litmus test (P0() and P1()) are not visible to external process P2(). + * This is likely to change soon. + *) + +{} + +P0(int *x, int *y, spinlock_t *mylock) +{ + spin_lock(mylock); + WRITE_ONCE(*x, 1); + WRITE_ONCE(*y, 1); + spin_unlock(mylock); +} + +P1(int *y, int *z, spinlock_t *mylock) +{ + int r0; + + spin_lock(mylock); + r0 = READ_ONCE(*y); + WRITE_ONCE(*z, 1); + spin_unlock(mylock); +} + +P2(int *x, int *z) +{ + int r1; + int r2; + + r2 = READ_ONCE(*z); + smp_mb(); + r1 = READ_ONCE(*x); +} + +exists (1:r0=1 /\ 2:r2=1 /\ 2:r1=0) -- 2.5.2