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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 13/17] rcutorture: Reduce priority of forward-progress testing Date: Wed, 29 Aug 2018 14:47:46 -0700 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180829214722.GA23411@linux.vnet.ibm.com> References: <20180829214722.GA23411@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18082921-0052-0000-0000-000003281C83 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009636; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000266; SDB=6.01080727; UDB=6.00557487; IPR=6.00860713; MB=3.00023001; MTD=3.00000008; XFM=3.00000015; UTC=2018-08-29 21:47:56 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18082921-0053-0000-0000-00005DE5E2B6 Message-Id: <20180829214750.26972-13-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-08-29_06:,, 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=8.0.1-1807170000 definitions=main-1808290211 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On !SMP tests, the forward-progress kthread might prevent RCU's grace-period kthread from running, which would defeat RCU's forward-progress measures. On PREEMPT tests without RCU priority boosting, the forward-progress kthread might preempt a reader for an extended time period, which would also defeat RCU's forward-progress measures. This commit therefore reduced rcutorture's forward-progress kthread's priority in those cases. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 9622192ec5c9..ac487ea8d245 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1710,6 +1710,8 @@ static int rcu_torture_fwd_prog(void *args) static DEFINE_TORTURE_RANDOM(trs); VERBOSE_TOROUT_STRING("rcu_torture_fwd_progress task started"); + if (!IS_ENABLED(CONFIG_SMP) || !IS_ENABLED(CONFIG_RCU_BOOST)) + set_user_nice(current, MAX_NICE); if (cur_ops->call && cur_ops->sync && cur_ops->cb_barrier) { init_rcu_head_on_stack(&fcs.rh); cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb); -- 2.17.1