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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, joel@joelfernandes.org, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 08/13] rcutorture: Emphasize testing of single reader protection type Date: Mon, 25 Jun 2018 17:52:22 -0700 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180626005205.GA28179@linux.vnet.ibm.com> References: <20180626005205.GA28179@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18062600-0040-0000-0000-00000445293F X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009255; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000266; SDB=6.01052342; UDB=6.00539473; IPR=6.00830268; MB=3.00021856; MTD=3.00000008; XFM=3.00000015; UTC=2018-06-26 00:50:29 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18062600-0041-0000-0000-0000084B3EFF Message-Id: <20180626005227.30660-8-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-06-25_11:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1806260008 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For RCU implementations supporting multiple types of reader protection, rcutorture currently randomly selects the combinations of types of protection for each phase of each reader. The problem with this, for example, given the four kinds of protection for RCU-sched (local_irq_disable(), local_bh_disable(), preempt_disable(), and rcu_read_lock_sched()), the reader will be protected by a single mechanism only 25% of the time. We really heavier testing of single read-side mechanisms. This commit therefore uses only a single mechanism about 60% of the time, half of the time explicitly and one-eighth of the time by chance. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index f97757755207..aa0be7ec2a26 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -69,6 +69,7 @@ MODULE_AUTHOR("Paul E. McKenney and Josh Triplett > 8; + unsigned long randmask2 = randmask1 >> 1; WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT); - mask = mask & (torture_random(trsp) >> RCUTORTURE_RDR_SHIFT); + /* Half the time lots of bits, half the time only one bit. */ + if (randmask1 & 0x1) + mask = mask & randmask2; + else + mask = mask & (1 << (randmask2 % RCUTORTURE_RDR_NBITS)); if ((mask & RCUTORTURE_RDR_IRQ) && !(mask & RCUTORTURE_RDR_BH) && (oldmask & RCUTORTURE_RDR_BH)) -- 2.17.1