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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 12/17] rcutorture: Limit reader duration if irq or bh disabled Date: Wed, 29 Aug 2018 14:47:45 -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: 18082921-0040-0000-0000-0000046753F8 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: 18082921-0041-0000-0000-0000086E6DC8 Message-Id: <20180829214750.26972-12-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 There are debug checks in some environments that will complain if the duration of a bh-disabled region of code exceeds about 50 milliseconds. Because rcu_read_delay() can produce a 50-millisecond delay and because there could be up to eight reader segments with such delays, this commit limits the maximum delay to 10 milliseconds if either interrupts or softirqs are disabled. Reported-by: Thomas Gleixner Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index b98bb11d47a2..9622192ec5c9 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -323,7 +323,7 @@ static void rcu_read_delay(struct torture_random_state *rrsp) unsigned long started; unsigned long completed; const unsigned long shortdelay_us = 200; - const unsigned long longdelay_ms = 300; + unsigned long longdelay_ms = 300; unsigned long long ts; /* We want a short delay sometimes to make a reader delay the grace @@ -333,6 +333,8 @@ static void rcu_read_delay(struct torture_random_state *rrsp) if (!(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) { started = cur_ops->get_gp_seq(); ts = rcu_trace_clock_local(); + if (preempt_count() & (SOFTIRQ_MASK | HARDIRQ_MASK)) + longdelay_ms = 5; /* Avoid triggering BH limits. */ mdelay(longdelay_ms); completed = cur_ops->get_gp_seq(); do_trace_rcu_torture_read(cur_ops->name, NULL, ts, -- 2.17.1