From: 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,
Sangmoon Kim <sangmoon.kim@samsung.com>,
"Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 10/10] rcu/tree: Add a trace event for RCU CPU stall warnings
Date: Wed, 3 Mar 2021 16:00:19 -0800 [thread overview]
Message-ID: <20210304000019.22459-10-paulmck@kernel.org> (raw)
In-Reply-To: <20210303235958.GA22373@paulmck-ThinkPad-P72>
From: Sangmoon Kim <sangmoon.kim@samsung.com>
This commit adds a trace event which allows tracing the beginnings of RCU
CPU stall warnings on systems where sysctl_panic_on_rcu_stall is disabled.
The first parameter is the name of RCU flavor like other trace events.
The second parameter indicates whether this is a stall of an expedited
grace period, a self-detected stall of a normal grace period, or a stall
of a normal grace period detected by some CPU other than the one that
is stalled.
RCU CPU stall warnings are often caused by external-to-RCU issues,
for example, in interrupt handling or task scheduling. Therefore,
this event uses TRACE_EVENT, not TRACE_EVENT_RCU, to avoid requiring
those interested in tracing RCU CPU stalls to rebuild their kernels
with CONFIG_RCU_TRACE=y.
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Sangmoon Kim <sangmoon.kim@samsung.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/trace/events/rcu.h | 28 ++++++++++++++++++++++++++++
kernel/rcu/tree_exp.h | 1 +
kernel/rcu/tree_stall.h | 2 ++
3 files changed, 31 insertions(+)
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 5fc2940..c7711e9 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -432,6 +432,34 @@ TRACE_EVENT_RCU(rcu_fqs,
__entry->cpu, __entry->qsevent)
);
+/*
+ * Tracepoint for RCU stall events. Takes a string identifying the RCU flavor
+ * and a string identifying which function detected the RCU stall as follows:
+ *
+ * "StallDetected": Scheduler-tick detects other CPU's stalls.
+ * "SelfDetected": Scheduler-tick detects a current CPU's stall.
+ * "ExpeditedStall": Expedited grace period detects stalls.
+ */
+TRACE_EVENT(rcu_stall_warning,
+
+ TP_PROTO(const char *rcuname, const char *msg),
+
+ TP_ARGS(rcuname, msg),
+
+ TP_STRUCT__entry(
+ __field(const char *, rcuname)
+ __field(const char *, msg)
+ ),
+
+ TP_fast_assign(
+ __entry->rcuname = rcuname;
+ __entry->msg = msg;
+ ),
+
+ TP_printk("%s %s",
+ __entry->rcuname, __entry->msg)
+);
+
#endif /* #if defined(CONFIG_TREE_RCU) */
/*
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 6c6ff06..2796084 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -521,6 +521,7 @@ static void synchronize_rcu_expedited_wait(void)
if (rcu_stall_is_suppressed())
continue;
panic_on_rcu_stall();
+ trace_rcu_stall_warning(rcu_state.name, TPS("ExpeditedStall"));
pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {",
rcu_state.name);
ndetected = 0;
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 475b261..59b95cc 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -536,6 +536,7 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps)
* See Documentation/RCU/stallwarn.rst for info on how to debug
* RCU CPU stall warnings.
*/
+ trace_rcu_stall_warning(rcu_state.name, TPS("StallDetected"));
pr_err("INFO: %s detected stalls on CPUs/tasks:\n", rcu_state.name);
rcu_for_each_leaf_node(rnp) {
raw_spin_lock_irqsave_rcu_node(rnp, flags);
@@ -606,6 +607,7 @@ static void print_cpu_stall(unsigned long gps)
* See Documentation/RCU/stallwarn.rst for info on how to debug
* RCU CPU stall warnings.
*/
+ trace_rcu_stall_warning(rcu_state.name, TPS("SelfDetected"));
pr_err("INFO: %s self-detected stall on CPU\n", rcu_state.name);
raw_spin_lock_irqsave_rcu_node(rdp->mynode, flags);
print_cpu_stall_info(smp_processor_id());
--
2.9.5
prev parent reply other threads:[~2021-03-04 0:17 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-03 23:59 [PATCH tip/core/rcu 0/10] Miscellaneous fixes for v5.13 Paul E. McKenney
2021-03-04 0:00 ` [PATCH tip/core/rcu 01/10] rcu: Remove superfluous rdp fetch paulmck
2021-03-04 0:00 ` [PATCH tip/core/rcu 02/10] rcu: Fix CPU-offline trace in rcutree_dying_cpu paulmck
2021-03-04 0:00 ` [PATCH tip/core/rcu 03/10] rcu: Remove spurious instrumentation_end() in rcu_nmi_enter() paulmck
2021-03-04 0:00 ` [PATCH tip/core/rcu 04/10] rculist: Replace reference to atomic_ops.rst paulmck
2021-03-04 0:00 ` [PATCH tip/core/rcu 05/10] rcu: Fix kfree_rcu() docbook errors paulmck
2021-03-04 0:00 ` [PATCH tip/core/rcu 06/10] softirq: Don't try waking ksoftirqd before it has been spawned paulmck
2021-03-12 11:36 ` Frederic Weisbecker
2021-03-15 23:11 ` Paul E. McKenney
2021-03-04 0:00 ` [PATCH tip/core/rcu 07/10] rcu: Prevent dyntick-idle until ksoftirqd " paulmck
2021-03-11 23:23 ` Frederic Weisbecker
2021-03-11 23:34 ` Paul E. McKenney
2021-03-04 0:00 ` [PATCH tip/core/rcu 08/10] docs: Correctly spell Stephen Hemminger's name paulmck
2021-03-04 0:00 ` [PATCH tip/core/rcu 09/10] rcu: Add explicit barrier() to __rcu_read_unlock() paulmck
2021-03-04 0:00 ` paulmck [this message]
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