Merge tag 'trace-v5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from Steven Rostedt:
 "No new features this release. Mostly clean ups, restructuring and
  documentation.

   - Have ftrace_bug() show ftrace errors before the WARN, as the WARN
     will reboot the box before the error messages are printed if
     panic_on_warn is set.

   - Have traceoff_on_warn disable tracing sooner (before prints)

   - Write a message to the trace buffer that its being disabled when
     disable_trace_on_warning() is set.

   - Separate out synthetic events from histogram code to let it be used
     by other parts of the kernel.

   - More documentation on histogram design.

   - Other small fixes and clean ups"

* tag 'trace-v5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Remove obsolete PREEMPTIRQ_EVENTS kconfig option
  tracing/doc: Fix ascii-art in histogram-design.rst
  tracing: Add a trace print when traceoff_on_warning is triggered
  ftrace,bug: Improve traceoff_on_warn
  selftests/ftrace: Distinguish between hist and synthetic event checks
  tracing: Move synthetic events to a separate file
  tracing: Fix events.rst section numbering
  tracing/doc: Fix typos in histogram-design.rst
  tracing: Add hist_debug trace event files for histogram debugging
  tracing: Add histogram-design document
  tracing: Check state.disabled in synth event trace functions
  tracing/probe: reverse arguments to list_add
  tools/bootconfig: Add a summary of test cases and return error
  ftrace: show debugging information when panic_on_warn set

Author: torvalds

Documentation/trace/histogram-design.rst

@@ -249,15 +249,6 @@ config TRACE_PREEMPT_TOGGLE
 	  Enables hooks which will be called when preemption is first disabled,
 	  and last enabled.
 
-config PREEMPTIRQ_EVENTS
-	bool "Enable trace events for preempt and irq disable/enable"
-	select TRACE_IRQFLAGS
-	select TRACE_PREEMPT_TOGGLE if PREEMPTION
-	select GENERIC_TRACER
-	default n
-	help
-	  Enable tracing of disable and enable events for preemption and irqs.
-
 config IRQSOFF_TRACER
 	bool "Interrupts-off Latency Tracer"
 	default n
@@ -614,12 +605,30 @@ config TRACING_MAP
 	  generally used outside of that context, and is normally
 	  selected by tracers that use it.
 
+config SYNTH_EVENTS
+	bool "Synthetic trace events"
+	select TRACING
+	select DYNAMIC_EVENTS
+	default n
+	help
+	  Synthetic events are user-defined trace events that can be
+	  used to combine data from other trace events or in fact any
+	  data source.  Synthetic events can be generated indirectly
+	  via the trace() action of histogram triggers or directly
+	  by way of an in-kernel API.
+
+	  See Documentation/trace/events.rst or
+	  Documentation/trace/histogram.rst for details and examples.
+
+	  If in doubt, say N.
+
 config HIST_TRIGGERS
 	bool "Histogram triggers"
 	depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select TRACING_MAP
 	select TRACING
 	select DYNAMIC_EVENTS
+	select SYNTH_EVENTS
 	default n
 	help
 	  Hist triggers allow one or more arbitrary trace event fields
@@ -815,7 +824,7 @@ config PREEMPTIRQ_DELAY_TEST
 
 config SYNTH_EVENT_GEN_TEST
 	tristate "Test module for in-kernel synthetic event generation"
-	depends on HIST_TRIGGERS
+	depends on SYNTH_EVENTS
 	help
           This option creates a test module to check the base
           functionality of in-kernel synthetic event definition and
@@ -838,6 +847,29 @@ config KPROBE_EVENT_GEN_TEST
 
 	  If unsure, say N.
 
+config HIST_TRIGGERS_DEBUG
+	bool "Hist trigger debug support"
+	depends on HIST_TRIGGERS
+	help
+          Add "hist_debug" file for each event, which when read will
+          dump out a bunch of internal details about the hist triggers
+          defined on that event.
+
+          The hist_debug file serves a couple of purposes:
+
+            - Helps developers verify that nothing is broken.
+
+            - Provides educational information to support the details
+              of the hist trigger internals as described by
+              Documentation/trace/histogram-design.rst.
+
+          The hist_debug output only covers the data structures
+          related to the histogram definitions themselves and doesn't
+          display the internals of map buckets or variable values of
+          running histograms.
+
+          If unsure, say N.
+
 endif # FTRACE
 
 endif # TRACING_SUPPORT

kernel/trace/Kconfig

@@ -72,6 +72,7 @@ endif
 obj-$(CONFIG_EVENT_TRACING) += trace_events_filter.o
 obj-$(CONFIG_EVENT_TRACING) += trace_events_trigger.o
 obj-$(CONFIG_TRACE_EVENT_INJECT) += trace_events_inject.o
+obj-$(CONFIG_SYNTH_EVENTS) += trace_events_synth.o
 obj-$(CONFIG_HIST_TRIGGERS) += trace_events_hist.o
 obj-$(CONFIG_BPF_EVENTS) += bpf_trace.o
 obj-$(CONFIG_KPROBE_EVENTS) += trace_kprobe.o

kernel/trace/Makefile

@@ -2016,14 +2016,14 @@ void ftrace_bug(int failed, struct dyn_ftrace *rec)
 {
 	unsigned long ip = rec ? rec->ip : 0;
 
+	pr_info("------------[ ftrace bug ]------------\n");
+
 	switch (failed) {
 	case -EFAULT:
-		FTRACE_WARN_ON_ONCE(1);
 		pr_info("ftrace faulted on modifying ");
 		print_ip_sym(KERN_INFO, ip);
 		break;
 	case -EINVAL:
-		FTRACE_WARN_ON_ONCE(1);
 		pr_info("ftrace failed to modify ");
 		print_ip_sym(KERN_INFO, ip);
 		print_ip_ins(" actual:   ", (unsigned char *)ip);
@@ -2034,12 +2034,10 @@ void ftrace_bug(int failed, struct dyn_ftrace *rec)
 		}
 		break;
 	case -EPERM:
-		FTRACE_WARN_ON_ONCE(1);
 		pr_info("ftrace faulted on writing ");
 		print_ip_sym(KERN_INFO, ip);
 		break;
 	default:
-		FTRACE_WARN_ON_ONCE(1);
 		pr_info("ftrace faulted on unknown error ");
 		print_ip_sym(KERN_INFO, ip);
 	}
@@ -2066,6 +2064,8 @@ void ftrace_bug(int failed, struct dyn_ftrace *rec)
 		ip = ftrace_get_addr_curr(rec);
 		pr_cont("\n expected tramp: %lx\n", ip);
 	}
+
+	FTRACE_WARN_ON_ONCE(1);
 }
 
 static int ftrace_check_record(struct dyn_ftrace *rec, bool enable, bool update)

kernel/trace/ftrace.c

@@ -1299,8 +1299,11 @@ EXPORT_SYMBOL_GPL(tracing_off);
 
 void disable_trace_on_warning(void)
 {
-	if (__disable_trace_on_warning)
+	if (__disable_trace_on_warning) {
+		trace_array_printk_buf(global_trace.array_buffer.buffer, _THIS_IP_,
+			"Disabling tracing due to warning\n");
 		tracing_off();
+	}
 }
 
 /**

kernel/trace/trace.c

@@ -1661,6 +1661,7 @@ extern struct list_head ftrace_events;
 
 extern const struct file_operations event_trigger_fops;
 extern const struct file_operations event_hist_fops;
+extern const struct file_operations event_hist_debug_fops;
 extern const struct file_operations event_inject_fops;
 
 #ifdef CONFIG_HIST_TRIGGERS

kernel/trace/trace.h

@@ -2208,6 +2208,10 @@ event_create_dir(struct dentry *parent, struct trace_event_file *file)
 #ifdef CONFIG_HIST_TRIGGERS
 	trace_create_file("hist", 0444, file->dir, file,
 			  &event_hist_fops);
+#endif
+#ifdef CONFIG_HIST_TRIGGERS_DEBUG
+	trace_create_file("hist_debug", 0444, file->dir, file,
+			  &event_hist_debug_fops);
 #endif
 	trace_create_file("format", 0444, file->dir, call,
 			  &ftrace_event_format_fops);