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authorSangmoon Kim <sangmoon.kim@samsung.com>2021-03-02 20:55:15 +0900
committerPaul E. McKenney <paulmck@kernel.org>2021-03-15 13:53:24 -0700
commit565cfb9e64dac1aadf7e2130fcda19a1c018df66 (patch)
tree07a85851e876c0cb1b270e51f6677c5fa9e44180
parentrcu: Add explicit barrier() to __rcu_read_unlock() (diff)
downloadlinux-dev-565cfb9e64dac1aadf7e2130fcda19a1c018df66.tar.xz
linux-dev-565cfb9e64dac1aadf7e2130fcda19a1c018df66.zip
rcu/tree: Add a trace event for RCU CPU stall warnings
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>
-rw-r--r--include/trace/events/rcu.h28
-rw-r--r--kernel/rcu/tree_exp.h1
-rw-r--r--kernel/rcu/tree_stall.h2
3 files changed, 31 insertions, 0 deletions
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 5fc29400e1a2..c7711e9b6900 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 6c6ff06d4ae6..2796084ef85a 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 475b26171b20..59b95cc5cbdf 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());