rcu: Add failure tracing to rcutorture

Trace the rcutorture RCU accesses and dump the trace buffer when the
first failure is detected.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index cd1ad4b04c6d69ac2d2554d5815df49bdac85f98..8d315b013e37371238a3daac82aa9f7f3e2d4725 100644 (file)
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -51,6 +51,8 @@ extern int rcutorture_runnable; /* for sysctl */
 #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
 extern void rcutorture_record_test_transition(void);
 extern void rcutorture_record_progress(unsigned long vernum);
+extern void do_trace_rcu_torture_read(char *rcutorturename,
+                                     struct rcu_head *rhp);
 #else
 static inline void rcutorture_record_test_transition(void)
 {
@@ -58,6 +60,12 @@ static inline void rcutorture_record_test_transition(void)
 static inline void rcutorture_record_progress(unsigned long vernum)
 {
 }
+#ifdef CONFIG_RCU_TRACE
+extern void do_trace_rcu_torture_read(char *rcutorturename,
+                                     struct rcu_head *rhp);
+#else
+#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
+#endif
 #endif
 
 #define UINT_CMP_GE(a, b)      (UINT_MAX / 2 >= (a) - (b))

diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index e5771804c5073b0eebd7893d921e756e3976167a..172620a92b1a86afaea48167ca8a85222a8f33e3 100644 (file)
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -437,6 +437,31 @@ TRACE_EVENT(rcu_batch_end,
                  __entry->rcuname, __entry->callbacks_invoked)
 );
 
+/*
+ * Tracepoint for rcutorture readers.  The first argument is the name
+ * of the RCU flavor from rcutorture's viewpoint and the second argument
+ * is the callback address.
+ */
+TRACE_EVENT(rcu_torture_read,
+
+       TP_PROTO(char *rcutorturename, struct rcu_head *rhp),
+
+       TP_ARGS(rcutorturename, rhp),
+
+       TP_STRUCT__entry(
+               __field(char *, rcutorturename)
+               __field(struct rcu_head *, rhp)
+       ),
+
+       TP_fast_assign(
+               __entry->rcutorturename = rcutorturename;
+               __entry->rhp = rhp;
+       ),
+
+       TP_printk("%s torture read %p",
+                 __entry->rcutorturename, __entry->rhp)
+);
+
 #else /* #ifdef CONFIG_RCU_TRACE */
 
 #define trace_rcu_grace_period(rcuname, gpnum, gpevent) do { } while (0)
@@ -452,6 +477,7 @@ TRACE_EVENT(rcu_batch_end,
 #define trace_rcu_invoke_callback(rcuname, rhp) do { } while (0)
 #define trace_rcu_invoke_kfree_callback(rcuname, rhp, offset) do { } while (0)
 #define trace_rcu_batch_end(rcuname, callbacks_invoked) do { } while (0)
+#define trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
 
 #endif /* #else #ifdef CONFIG_RCU_TRACE */
 

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index c5b98e565aee28e711c71f5acd49cd3a34b99530..92e771d7b44b7f7853aeb01d06638263b3d032fa 100644 (file)
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -316,3 +316,13 @@ struct debug_obj_descr rcuhead_debug_descr = {
 };
 EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+
+#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
+void do_trace_rcu_torture_read(char *rcutorturename, struct rcu_head *rhp)
+{
+       trace_rcu_torture_read(rcutorturename, rhp);
+}
+EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
+#else
+#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
+#endif

diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 764825c2685c494b6839acaac1b25e500db610c5..df35228e743b79db017b4a856b19b308050b8ce8 100644 (file)
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -913,6 +913,18 @@ rcu_torture_fakewriter(void *arg)
        return 0;
 }
 
+void rcutorture_trace_dump(void)
+{
+       static atomic_t beenhere = ATOMIC_INIT(0);
+
+       if (atomic_read(&beenhere))
+               return;
+       if (atomic_xchg(&beenhere, 1) != 0)
+               return;
+       do_trace_rcu_torture_read(cur_ops->name, (struct rcu_head *)~0UL);
+       ftrace_dump(DUMP_ALL);
+}
+
 /*
  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
  * incrementing the corresponding element of the pipeline array.  The
@@ -934,6 +946,7 @@ static void rcu_torture_timer(unsigned long unused)
                                  rcu_read_lock_bh_held() ||
                                  rcu_read_lock_sched_held() ||
                                  srcu_read_lock_held(&srcu_ctl));
+       do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
        if (p == NULL) {
                /* Leave because rcu_torture_writer is not yet underway */
                cur_ops->readunlock(idx);
@@ -951,6 +964,8 @@ static void rcu_torture_timer(unsigned long unused)
                /* Should not happen, but... */
                pipe_count = RCU_TORTURE_PIPE_LEN;
        }
+       if (pipe_count > 1)
+               rcutorture_trace_dump();
        __this_cpu_inc(rcu_torture_count[pipe_count]);
        completed = cur_ops->completed() - completed;
        if (completed > RCU_TORTURE_PIPE_LEN) {
@@ -994,6 +1009,7 @@ rcu_torture_reader(void *arg)
                                          rcu_read_lock_bh_held() ||
                                          rcu_read_lock_sched_held() ||
                                          srcu_read_lock_held(&srcu_ctl));
+               do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
                if (p == NULL) {
                        /* Wait for rcu_torture_writer to get underway */
                        cur_ops->readunlock(idx);
@@ -1009,6 +1025,8 @@ rcu_torture_reader(void *arg)
                        /* Should not happen, but... */
                        pipe_count = RCU_TORTURE_PIPE_LEN;
                }
+               if (pipe_count > 1)
+                       rcutorture_trace_dump();
                __this_cpu_inc(rcu_torture_count[pipe_count]);
                completed = cur_ops->completed() - completed;
                if (completed > RCU_TORTURE_PIPE_LEN) {