From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
mingo@kernel.org, jiangshanlai@gmail.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" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 09/19] rcu: Add quiescent states and boost states to show_rcu_gp_kthreads() output
Date: Tue, 11 May 2021 15:52:54 -0700 [thread overview]
Message-ID: <20210511225304.2893154-9-paulmck@kernel.org> (raw)
In-Reply-To: <20210511225241.GA2893003@paulmck-ThinkPad-P17-Gen-1>
This commit adds each rcu_node structure's ->qsmask and "bBEG" output
indicating whether: (1) There is a boost kthread, (2) A reader needs
to be (or is in the process of being) boosted, (3) A reader is blocking
an expedited grace period, and (4) A reader is blocking a normal grace
period. This helps diagnose RCU priority boosting failures.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/tree.h | 1 +
kernel/rcu/tree_plugin.h | 1 +
kernel/rcu/tree_stall.h | 12 +++++++++---
3 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 71821d59d95c..5fd0c443517e 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -115,6 +115,7 @@ struct rcu_node {
/* boosting for this rcu_node structure. */
unsigned int boost_kthread_status;
/* State of boost_kthread_task for tracing. */
+ unsigned long n_boosts; /* Number of boosts for this rcu_node structure. */
#ifdef CONFIG_RCU_NOCB_CPU
struct swait_queue_head nocb_gp_wq[2];
/* Place for rcu_nocb_kthread() to wait GP. */
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 2cbe8f8456e6..ef004cc7101d 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1098,6 +1098,7 @@ static int rcu_boost(struct rcu_node *rnp)
/* Lock only for side effect: boosts task t's priority. */
rt_mutex_lock(&rnp->boost_mtx);
rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */
+ rnp->n_boosts++;
return READ_ONCE(rnp->exp_tasks) != NULL ||
READ_ONCE(rnp->boost_tasks) != NULL;
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index a4e2bb3bdce7..c1f83864a18e 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -749,9 +749,15 @@ void show_rcu_gp_kthreads(void)
if (ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq),
READ_ONCE(rnp->gp_seq_needed)))
continue;
- pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld\n",
- rnp->grplo, rnp->grphi, (long)data_race(rnp->gp_seq),
- (long)data_race(rnp->gp_seq_needed));
+ pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld ->qsmask %#lx %c%c%c%c ->n_boosts %ld\n",
+ rnp->grplo, rnp->grphi,
+ (long)data_race(rnp->gp_seq), (long)data_race(rnp->gp_seq_needed),
+ data_race(rnp->qsmask),
+ ".b"[!!data_race(rnp->boost_kthread_task)],
+ ".B"[!!data_race(rnp->boost_tasks)],
+ ".E"[!!data_race(rnp->exp_tasks)],
+ ".G"[!!data_race(rnp->gp_tasks)],
+ data_race(rnp->n_boosts));
if (!rcu_is_leaf_node(rnp))
continue;
for_each_leaf_node_possible_cpu(rnp, cpu) {
--
2.31.1.189.g2e36527f23
next prev parent reply other threads:[~2021-05-11 22:53 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 22:52 [PATCH tip/core/rcu 0/19] Miscellaneous fixes for v5.14 Paul E. McKenney
2021-05-11 22:52 ` [PATCH tip/core/rcu 01/19] rcu: Fix typo in comment: kthead -> kthread Paul E. McKenney
2021-05-11 22:52 ` [PATCH tip/core/rcu 02/19] rcu: Remove the unused rcu_irq_exit_preempt() function Paul E. McKenney
2021-05-11 22:52 ` [PATCH tip/core/rcu 03/19] rcu: Improve tree.c comments and add code cleanups Paul E. McKenney
2021-05-11 22:52 ` [PATCH tip/core/rcu 04/19] rcu: Invoke rcu_spawn_core_kthreads() from rcu_spawn_gp_kthread() Paul E. McKenney
2021-05-11 22:52 ` [PATCH tip/core/rcu 05/19] rcu: Add ->rt_priority and ->gp_start to show_rcu_gp_kthreads() output Paul E. McKenney
2021-05-11 22:52 ` [PATCH tip/core/rcu 06/19] rcu: Add ->gp_max " Paul E. McKenney
2021-05-11 22:52 ` [PATCH tip/core/rcu 07/19] lockdep: Explicitly flag likely false-positive report Paul E. McKenney
2021-05-11 22:52 ` [PATCH tip/core/rcu 08/19] rcu: Reject RCU_LOCKDEP_WARN() false positives Paul E. McKenney
2021-05-11 22:52 ` Paul E. McKenney [this message]
2021-05-11 22:52 ` [PATCH tip/core/rcu 10/19] rcu: Make RCU priority boosting work on single-CPU rcu_node structures Paul E. McKenney
2021-05-11 22:52 ` [PATCH tip/core/rcu 11/19] rcu: Make show_rcu_gp_kthreads() dump rcu_node structures blocking GP Paul E. McKenney
2021-05-11 22:52 ` [PATCH tip/core/rcu 12/19] rcu: Restrict RCU_STRICT_GRACE_PERIOD to at most four CPUs Paul E. McKenney
2021-05-11 22:52 ` [PATCH tip/core/rcu 13/19] rcu: Make rcu_gp_cleanup() be noinline for tracing Paul E. McKenney
2021-05-11 22:52 ` [PATCH tip/core/rcu 14/19] rcu: Point to documentation of ordering guarantees Paul E. McKenney
2021-05-11 22:53 ` [PATCH tip/core/rcu 15/19] rcu: Create an unrcu_pointer() to remove __rcu from a pointer Paul E. McKenney
2021-05-11 22:53 ` [PATCH tip/core/rcu 16/19] sched/isolation: reconcile rcu_nocbs= and nohz_full= Paul E. McKenney
2021-05-11 22:53 ` [PATCH tip/core/rcu 17/19] rcu: Improve comments describing RCU read-side critical sections Paul E. McKenney
2021-05-11 22:53 ` [PATCH tip/core/rcu 18/19] rcu: Remove obsolete rcu_read_unlock() deadlock commentary Paul E. McKenney
2021-05-11 22:53 ` [PATCH tip/core/rcu 19/19] rcu: Add missing __releases() annotation Paul E. McKenney
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