Merge tag 'trace-v4.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fixes from Steven Rostedt:
"This contains a few fixes and a clean up.

- a bad merge caused an "endif" to go in the wrong place in
scripts/Makefile.build

- softirq tracing fix for tracing that corrupts lockdep and causes a
false splat

- histogram documentation typo fixes

- fix a bad memory reference when passing in no filter to the filter
code

- simplify code by using the swap macro instead of open coding the
swap"

* tag 'trace-v4.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
tracing: Fix SKIP_STACK_VALIDATION=1 build due to bad merge with -mrecord-mcount
tracing: Fix some errors in histogram documentation
tracing: Use swap macro in update_max_tr
softirq: Reorder trace_softirqs_on to prevent lockdep splat
tracing: Check for no filter when processing event filters

Documentation/trace/histogram.txt

···
 associated event field will be saved in a variable but won't be summed
 as a value:
 
-  # echo 'hist:keys=next_pid:ts1=common_timestamp ... >> event/trigger
+  # echo 'hist:keys=next_pid:ts1=common_timestamp ...' >> event/trigger
 
 Multiple variables can be assigned at the same time.  The below would
 result in both ts0 and b being created as variables, with both
 common_timestamp and field1 additionally being summed as values:
 
-  # echo 'hist:keys=pid:vals=$ts0,$b:ts0=common_timestamp,b=field1 ... >> \
+  # echo 'hist:keys=pid:vals=$ts0,$b:ts0=common_timestamp,b=field1 ...' >> \
 	event/trigger
 
 Note that variable assignments can appear either preceding or
 following their use.  The command below behaves identically to the
 command above:
 
-  # echo 'hist:keys=pid:ts0=common_timestamp,b=field1:vals=$ts0,$b ... >> \
+  # echo 'hist:keys=pid:ts0=common_timestamp,b=field1:vals=$ts0,$b ...' >> \
 	event/trigger
 
 Any number of variables not bound to a 'vals=' prefix can also be
 assigned by simply separating them with colons.  Below is the same
 thing but without the values being summed in the histogram:
 
-  # echo 'hist:keys=pid:ts0=common_timestamp:b=field1 ... >> event/trigger
+  # echo 'hist:keys=pid:ts0=common_timestamp:b=field1 ...' >> event/trigger
 
 Variables set as above can be referenced and used in expressions on
 another event.
 
 For example, here's how a latency can be calculated:
 
-  # echo 'hist:keys=pid,prio:ts0=common_timestamp ... >> event1/trigger
-  # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp-$ts0 ... >> event2/trigger
+  # echo 'hist:keys=pid,prio:ts0=common_timestamp ...' >> event1/trigger
+  # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp-$ts0 ...' >> event2/trigger
 
 In the first line above, the event's timetamp is saved into the
 variable ts0.  In the next line, ts0 is subtracted from the second
···
 makes use of the wakeup_lat variable to compute a combined latency
 using the same key and variable from yet another event:
 
-  # echo 'hist:key=pid:wakeupswitch_lat=$wakeup_lat+$switchtime_lat ... >> event3/trigger
+  # echo 'hist:key=pid:wakeupswitch_lat=$wakeup_lat+$switchtime_lat ...' >> event3/trigger
 
 2.2.2 Synthetic Events
 ----------------------
···
 At this point, there isn't yet an actual 'wakeup_latency' event
 instantiated in the event subsytem - for this to happen, a 'hist
 trigger action' needs to be instantiated and bound to actual fields
-and variables defined on other events (see Section 6.3.3 below).
+and variables defined on other events (see Section 2.2.3 below on
+how that is done using hist trigger 'onmatch' action). Once that is
+done, the 'wakeup_latency' synthetic event instance is created.
 
-Once that is done, an event instance is created, and a histogram can
-be defined using it:
+A histogram can now be defined for the new synthetic event:
 
   # echo 'hist:keys=pid,prio,lat.log2:sort=pid,lat' >> \
         /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger
···
     back to that pid, the timestamp difference is calculated.  If the
     resulting latency, stored in wakeup_lat, exceeds the current
     maximum latency, the values specified in the save() fields are
-    recoreded:
+    recorded:
 
     # echo 'hist:keys=pid:ts0=common_timestamp.usecs \
             if comm=="cyclictest"' >> \

kernel/softirq.c

···
 {
 	lockdep_assert_irqs_disabled();
 
+	if (preempt_count() == cnt)
+		trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
+
 	if (softirq_count() == (cnt & SOFTIRQ_MASK))
 		trace_softirqs_on(_RET_IP_);
-	preempt_count_sub(cnt);
+
+	__preempt_count_sub(cnt);
 }
 
 /*

kernel/trace/trace.c

···
 void
 update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
 {
-	struct ring_buffer *buf;
-
 	if (tr->stop_count)
 		return;
 
···
 
 	arch_spin_lock(&tr->max_lock);
 
-	buf = tr->trace_buffer.buffer;
-	tr->trace_buffer.buffer = tr->max_buffer.buffer;
-	tr->max_buffer.buffer = buf;
+	swap(tr->trace_buffer.buffer, tr->max_buffer.buffer);
 
 	__update_max_tr(tr, tsk, cpu);
 	arch_spin_unlock(&tr->max_lock);

kernel/trace/trace_events_filter.c

···
 	C(TOO_MANY_PREDS,	"Too many terms in predicate expression"), \
 	C(INVALID_FILTER,	"Meaningless filter expression"),	\
 	C(IP_FIELD_ONLY,	"Only 'ip' field is supported for function trace"), \
-	C(INVALID_VALUE,	"Invalid value (did you forget quotes)?"),
+	C(INVALID_VALUE,	"Invalid value (did you forget quotes)?"), \
+	C(NO_FILTER,		"No filter found"),
 
 #undef C
 #define C(a, b)		FILT_ERR_##a
···
 	if (top != op_stack) {
 		/* Too many '(' */
 		parse_error(pe, FILT_ERR_TOO_MANY_OPEN, ptr - str);
+		goto out_free;
+	}
+
+	if (!N) {
+		/* No program? */
+		ret = -EINVAL;
+		parse_error(pe, FILT_ERR_NO_FILTER, ptr - str);
 		goto out_free;
 	}
 

scripts/Makefile.build

···
 	     "$(CC_FLAGS_FTRACE)" ]; then			\
 		$(sub_cmd_record_mcount)			\
 	fi;
+endif # -record-mcount
 endif # CONFIG_FTRACE_MCOUNT_RECORD
 
 ifdef CONFIG_STACK_VALIDATION
···
 ifdef CONFIG_RETPOLINE
 ifneq ($(RETPOLINE_CFLAGS),)
   objtool_args += --retpoline
-endif
 endif
 endif