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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 17/17] rcutorture: Maintain self-propagating CB only during forward-progress test Date: Wed, 29 Aug 2018 14:47:50 -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: 18082921-0060-0000-0000-000002A65FEE 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: 18082921-0061-0000-0000-000046559E91 Message-Id: <20180829214750.26972-17-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 The current forward-progress testing maintains a self-propagating callback during the full test. This could result in false negatives for stutter-end checking, where it might appear that RCU was clearing out old callbacks only because it was being continually motivated by the self-propagating callback. This commit therefore shuts down the self-propagating callback at the end of each forward-progress test interval. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index ae10ad531993..a02a2f21386b 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1706,7 +1706,7 @@ static int rcu_torture_fwd_prog(void *args) { unsigned long cver; unsigned long dur; - struct fwd_cb_state fcs = { .stop = 0 }; + struct fwd_cb_state fcs; unsigned long gps; int idx; int sd; @@ -1722,11 +1722,14 @@ static int rcu_torture_fwd_prog(void *args) 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); selfpropcb = true; } do { schedule_timeout_interruptible(fwd_progress_holdoff * HZ); + if (selfpropcb) { + WRITE_ONCE(fcs.stop, 0); + cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb); + } cver = READ_ONCE(rcu_torture_current_version); gps = cur_ops->get_gp_seq(); sd = cur_ops->stall_dur() + 1; @@ -1748,13 +1751,15 @@ static int rcu_torture_fwd_prog(void *args) WARN_ON(!cver && gps < 2); pr_alert("%s: Duration %ld cver %ld gps %ld\n", __func__, dur, cver, gps); } + if (selfpropcb) { + WRITE_ONCE(fcs.stop, 1); + cur_ops->sync(); /* Wait for running CB to complete. */ + cur_ops->cb_barrier(); /* Wait for queued callbacks. */ + } /* Avoid slow periods, better to test when busy. */ stutter_wait("rcu_torture_fwd_prog"); } while (!torture_must_stop()); if (selfpropcb) { - WRITE_ONCE(fcs.stop, 1); - cur_ops->sync(); /* Wait for running callback to complete. */ - cur_ops->cb_barrier(); /* Wait for queued callbacks. */ WARN_ON(READ_ONCE(fcs.stop) != 2); destroy_rcu_head_on_stack(&fcs.rh); } -- 2.17.1