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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-08-15 01:24:26 +0200
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-09-23 18:18:13 +0200
commit9261dd0da6c6432f08670719069449c6efe4f7a9 (patch)
treeb8c95dd0e4751e3069e9263d6f46b86251d5dc35 /include/trace
parentrcu: Add tracing of normal (non-NOCB) grace-period requests (diff)
downloadlinux-9261dd0da6c6432f08670719069449c6efe4f7a9.tar.xz
linux-9261dd0da6c6432f08670719069449c6efe4f7a9.zip
rcu: Add tracing for rcuo no-CBs CPU wakeup handshake
Lost wakeups from call_rcu() to the rcuo kthreads can result in hangs that are difficult to diagnose. This commit therefore adds tracing to help pin down the cause of these hangs. Reported-by: Clark Williams <williams@redhat.com> Reported-by: Carsten Emde <C.Emde@osadl.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Add const per kbuild test robot's advice. ]
Diffstat (limited to 'include/trace')
-rw-r--r--include/trace/events/rcu.h37
1 files changed, 37 insertions, 0 deletions
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 98466c618ebc..4301cd9e3ee5 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -172,6 +172,42 @@ TRACE_EVENT(rcu_grace_period_init,
);
/*
+ * Tracepoint for RCU no-CBs CPU callback handoffs. This event is intended
+ * to assist debugging of these handoffs.
+ *
+ * The first argument is the name of the RCU flavor, and the second is
+ * the number of the offloaded CPU are extracted. The third and final
+ * argument is a string as follows:
+ *
+ * "WakeEmpty": Wake rcuo kthread, first CB to empty list.
+ * "WakeOvf": Wake rcuo kthread, CB list is huge.
+ * "WakeNot": Don't wake rcuo kthread.
+ * "WakeNotPoll": Don't wake rcuo kthread because it is polling.
+ * "WokeEmpty": rcuo kthread woke to find empty list.
+ * "WokeNonEmpty": rcuo kthread woke to find non-empty list.
+ */
+TRACE_EVENT(rcu_nocb_wake,
+
+ TP_PROTO(const char *rcuname, int cpu, const char *reason),
+
+ TP_ARGS(rcuname, cpu, reason),
+
+ TP_STRUCT__entry(
+ __field(const char *, rcuname)
+ __field(int, cpu)
+ __field(const char *, reason)
+ ),
+
+ TP_fast_assign(
+ __entry->rcuname = rcuname;
+ __entry->cpu = cpu;
+ __entry->reason = reason;
+ ),
+
+ TP_printk("%s %d %s", __entry->rcuname, __entry->cpu, __entry->reason)
+);
+
+/*
* Tracepoint for tasks blocking within preemptible-RCU read-side
* critical sections. Track the type of RCU (which one day might
* include SRCU), the grace-period number that the task is blocking
@@ -667,6 +703,7 @@ TRACE_EVENT(rcu_barrier,
#define trace_rcu_future_grace_period(rcuname, gpnum, completed, c, \
level, grplo, grphi, event) \
do { } while (0)
+#define trace_rcu_nocb_wake(rcuname, cpu, reason) do { } while (0)
#define trace_rcu_preempt_task(rcuname, pid, gpnum) do { } while (0)
#define trace_rcu_unlock_preempted_task(rcuname, gpnum, pid) do { } while (0)
#define trace_rcu_quiescent_state_report(rcuname, gpnum, mask, qsmask, level, \