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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 08/17] rcutorture: Dump grace-period diagnostics upon forward-progress OOM Date: Sun, 11 Nov 2018 12:20:18 -0800 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181111201956.GA11935@linux.ibm.com> References: <20181111201956.GA11935@linux.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18111120-0052-0000-0000-00000354249E X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010028; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000270; SDB=6.01116031; UDB=6.00578740; IPR=6.00896132; MB=3.00024115; MTD=3.00000008; XFM=3.00000015; UTC=2018-11-11 20:20:32 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18111120-0053-0000-0000-00005EBB30F1 Message-Id: <20181111202027.13585-8-paulmck@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-11-11_13:,, 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-1811110194 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This commit adds an OOM notifier during rcutorture forward-progress testing. If this notifier is invoked, it dumps out some grace-period state to help debug the forward-progress problem. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcu.h | 2 ++ kernel/rcu/rcutorture.c | 31 ++++++++++++++++++++++++++++--- kernel/rcu/tree.c | 20 ++++++++++++++++++++ 3 files changed, 50 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 0f0f5ae8c3d4..a393e24a9195 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -526,12 +526,14 @@ srcu_batches_completed(struct srcu_struct *sp) { return 0; } static inline void rcu_force_quiescent_state(void) { } static inline void show_rcu_gp_kthreads(void) { } static inline int rcu_get_gp_kthreads_prio(void) { return 0; } +static inline void rcu_fwd_progress_check(unsigned long j) { } #else /* #ifdef CONFIG_TINY_RCU */ unsigned long rcu_get_gp_seq(void); unsigned long rcu_exp_batches_completed(void); unsigned long srcu_batches_completed(struct srcu_struct *sp); void show_rcu_gp_kthreads(void); int rcu_get_gp_kthreads_prio(void); +void rcu_fwd_progress_check(unsigned long j); void rcu_force_quiescent_state(void); extern struct workqueue_struct *rcu_gp_wq; extern struct workqueue_struct *rcu_par_gp_wq; diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index c4fd61dccedb..f28b88ecb47a 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -56,6 +56,7 @@ #include #include #include +#include #include "rcu.h" @@ -1624,6 +1625,7 @@ static struct rcu_fwd_cb *rcu_fwd_cb_head; static struct rcu_fwd_cb **rcu_fwd_cb_tail = &rcu_fwd_cb_head; static long n_launders_cb; static unsigned long rcu_fwd_startat; +static bool rcu_fwd_emergency_stop; #define MAX_FWD_CB_JIFFIES (8 * HZ) /* Maximum CB test duration. */ #define MIN_FWD_CB_LAUNDERS 3 /* This many CB invocations to count. */ #define MIN_FWD_CBS_LAUNDERED 100 /* Number of counted CBs. */ @@ -1681,7 +1683,8 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries) dur = sd4 + torture_random(&trs) % (sd - sd4); WRITE_ONCE(rcu_fwd_startat, jiffies); stopat = rcu_fwd_startat + dur; - while (time_before(jiffies, stopat) && !torture_must_stop()) { + while (time_before(jiffies, stopat) && + !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) { idx = cur_ops->readlock(); udelay(10); cur_ops->readunlock(idx); @@ -1689,7 +1692,8 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries) cond_resched(); } (*tested_tries)++; - if (!time_before(jiffies, stopat) && !torture_must_stop()) { + if (!time_before(jiffies, stopat) && + !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) { (*tested)++; cver = READ_ONCE(rcu_torture_current_version) - cver; gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps); @@ -1739,7 +1743,8 @@ static void rcu_torture_fwd_prog_cr(void) n_launders_hist[i] = 0; cver = READ_ONCE(rcu_torture_current_version); gps = cur_ops->get_gp_seq(); - while (time_before(jiffies, stopat) && !torture_must_stop()) { + while (time_before(jiffies, stopat) && + !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) { rfcp = READ_ONCE(rcu_fwd_cb_head); rfcpn = NULL; if (rfcp) @@ -1796,6 +1801,23 @@ static void rcu_torture_fwd_prog_cr(void) } } + +/* + * OOM notifier, but this only prints diagnostic information for the + * current forward-progress test. + */ +static int rcutorture_oom_notify(struct notifier_block *self, + unsigned long notused, void *nfreed) +{ + rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rcu_fwd_startat) / 2)); + WRITE_ONCE(rcu_fwd_emergency_stop, true); + return NOTIFY_OK; +} + +static struct notifier_block rcutorture_oom_nb = { + .notifier_call = rcutorture_oom_notify +}; + /* Carry out grace-period forward-progress testing. */ static int rcu_torture_fwd_prog(void *args) { @@ -1808,8 +1830,11 @@ static int rcu_torture_fwd_prog(void *args) set_user_nice(current, MAX_NICE); do { schedule_timeout_interruptible(fwd_progress_holdoff * HZ); + WRITE_ONCE(rcu_fwd_emergency_stop, false); + register_oom_notifier(&rcutorture_oom_nb); rcu_torture_fwd_prog_nr(&tested, &tested_tries); rcu_torture_fwd_prog_cr(); + unregister_oom_notifier(&rcutorture_oom_nb); /* Avoid slow periods, better to test when busy. */ stutter_wait("rcu_torture_fwd_prog"); diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 121f833acd04..6f04352011d7 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2654,6 +2654,26 @@ rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp) raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } +/* + * Do a forward-progress check for rcutorture. This is normally invoked + * due to an OOM event. The argument "j" gives the time period during + * which rcutorture would like progress to have been made. + */ +void rcu_fwd_progress_check(unsigned long j) +{ + struct rcu_data *rdp; + + if (rcu_gp_in_progress()) { + show_rcu_gp_kthreads(); + } else { + preempt_disable(); + rdp = this_cpu_ptr(&rcu_data); + rcu_check_gp_start_stall(rdp->mynode, rdp, j); + preempt_enable(); + } +} +EXPORT_SYMBOL_GPL(rcu_fwd_progress_check); + /* * This does the RCU core processing work for the specified rcu_data * structures. This may be called only from the CPU to whom the rdp -- 2.17.1