[GIT PULL] tracing: Documentation updates and minor bug fix

[Steven Rostedt]

Linus,

The first two patches fix the debugfs README file to reflect better
the new features added to 3.14.

The third patch is a minor bugfix to the trace_puts() functions that
will crash the system if a developer adds one before the tracing system
is setup. It also affects trace_printk() if it has no arguments, as
the code will convert it to a trace_puts() as well. Note, this bug
will not affect unmodified kernels, as trace_printk() and trace_puts()
should only be used by developers for testing.

Please pull the latest trace-fixes-3.14 tree, which can be found at:


  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
trace-fixes-3.14

Tag SHA1: 14cc12e3c68e42cd2afb8f7e7beb7a570c22e2f8
Head SHA1: 3132e107d608f8753240d82d61303c500fd515b4


Steven Rostedt (Red Hat) (2):
      tracing: Fix formatting of trace README file
      tracing: Check if tracing is enabled in trace_puts()

Tom Zanussi (1):
      tracing/README: Add event file usage to tracing mini-HOWTO

----
 kernel/trace/trace.c | 113 ++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 81 insertions(+), 32 deletions(-)
---------------------------
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 20c755e..815c878 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -455,6 +455,9 @@ int __trace_puts(unsigned long ip, const char *str, int size)
 	unsigned long irq_flags;
 	int alloc;
 
+	if (unlikely(tracing_selftest_running || tracing_disabled))
+		return 0;
+
 	alloc = sizeof(*entry) + size + 2; /* possible \n added */
 
 	local_save_flags(irq_flags);
@@ -495,6 +498,9 @@ int __trace_bputs(unsigned long ip, const char *str)
 	unsigned long irq_flags;
 	int size = sizeof(struct bputs_entry);
 
+	if (unlikely(tracing_selftest_running || tracing_disabled))
+		return 0;
+
 	local_save_flags(irq_flags);
 	buffer = global_trace.trace_buffer.buffer;
 	event = trace_buffer_lock_reserve(buffer, TRACE_BPUTS, size,
@@ -3519,60 +3525,103 @@ static const char readme_msg[] =
 	"  instances\t\t- Make sub-buffers with: mkdir instances/foo\n"
 	"\t\t\t  Remove sub-buffer with rmdir\n"
 	"  trace_options\t\t- Set format or modify how tracing happens\n"
-	"\t\t\t  Disable an option by adding a suffix 'no' to the option name\n"
+	"\t\t\t  Disable an option by adding a suffix 'no' to the\n"
+	"\t\t\t  option name\n"
 #ifdef CONFIG_DYNAMIC_FTRACE
 	"\n  available_filter_functions - list of functions that can be filtered on\n"
-	"  set_ftrace_filter\t- echo function name in here to only trace these functions\n"
-	"            accepts: func_full_name, *func_end, func_begin*, *func_middle*\n"
-	"            modules: Can select a group via module\n"
-	"             Format: :mod:<module-name>\n"
-	"             example: echo :mod:ext3 > set_ftrace_filter\n"
-	"            triggers: a command to perform when function is hit\n"
-	"              Format: <function>:<trigger>[:count]\n"
-	"             trigger: traceon, traceoff\n"
-	"                      enable_event:<system>:<event>\n"
-	"                      disable_event:<system>:<event>\n"
+	"  set_ftrace_filter\t- echo function name in here to only trace these\n"
+	"\t\t\t  functions\n"
+	"\t     accepts: func_full_name, *func_end, func_begin*, *func_middle*\n"
+	"\t     modules: Can select a group via module\n"
+	"\t      Format: :mod:<module-name>\n"
+	"\t     example: echo :mod:ext3 > set_ftrace_filter\n"
+	"\t    triggers: a command to perform when function is hit\n"
+	"\t      Format: <function>:<trigger>[:count]\n"
+	"\t     trigger: traceon, traceoff\n"
+	"\t\t      enable_event:<system>:<event>\n"
+	"\t\t      disable_event:<system>:<event>\n"
 #ifdef CONFIG_STACKTRACE
-	"                      stacktrace\n"
+	"\t\t      stacktrace\n"
 #endif
 #ifdef CONFIG_TRACER_SNAPSHOT
-	"                      snapshot\n"
+	"\t\t      snapshot\n"
 #endif
-	"             example: echo do_fault:traceoff > set_ftrace_filter\n"
-	"                      echo do_trap:traceoff:3 > set_ftrace_filter\n"
-	"             The first one will disable tracing every time do_fault is hit\n"
-	"             The second will disable tracing at most 3 times when do_trap is hit\n"
-	"               The first time do trap is hit and it disables tracing, the counter\n"
-	"               will decrement to 2. If tracing is already disabled, the counter\n"
-	"               will not decrement. It only decrements when the trigger did work\n"
-	"             To remove trigger without count:\n"
-	"               echo '!<function>:<trigger> > set_ftrace_filter\n"
-	"             To remove trigger with a count:\n"
-	"               echo '!<function>:<trigger>:0 > set_ftrace_filter\n"
+	"\t     example: echo do_fault:traceoff > set_ftrace_filter\n"
+	"\t              echo do_trap:traceoff:3 > set_ftrace_filter\n"
+	"\t     The first one will disable tracing every time do_fault is hit\n"
+	"\t     The second will disable tracing at most 3 times when do_trap is hit\n"
+	"\t       The first time do trap is hit and it disables tracing, the\n"
+	"\t       counter will decrement to 2. If tracing is already disabled,\n"
+	"\t       the counter will not decrement. It only decrements when the\n"
+	"\t       trigger did work\n"
+	"\t     To remove trigger without count:\n"
+	"\t       echo '!<function>:<trigger> > set_ftrace_filter\n"
+	"\t     To remove trigger with a count:\n"
+	"\t       echo '!<function>:<trigger>:0 > set_ftrace_filter\n"
 	"  set_ftrace_notrace\t- echo function name in here to never trace.\n"
-	"            accepts: func_full_name, *func_end, func_begin*, *func_middle*\n"
-	"            modules: Can select a group via module command :mod:\n"
-	"            Does not accept triggers\n"
+	"\t    accepts: func_full_name, *func_end, func_begin*, *func_middle*\n"
+	"\t    modules: Can select a group via module command :mod:\n"
+	"\t    Does not accept triggers\n"
 #endif /* CONFIG_DYNAMIC_FTRACE */
 #ifdef CONFIG_FUNCTION_TRACER
-	"  set_ftrace_pid\t- Write pid(s) to only function trace those pids (function)\n"
+	"  set_ftrace_pid\t- Write pid(s) to only function trace those pids\n"
+	"\t\t    (function)\n"
 #endif
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	"  set_graph_function\t- Trace the nested calls of a function (function_graph)\n"
 	"  max_graph_depth\t- Trace a limited depth of nested calls (0 is unlimited)\n"
 #endif
 #ifdef CONFIG_TRACER_SNAPSHOT
-	"\n  snapshot\t\t- Like 'trace' but shows the content of the static snapshot buffer\n"
-	"\t\t\t  Read the contents for more information\n"
+	"\n  snapshot\t\t- Like 'trace' but shows the content of the static\n"
+	"\t\t\t  snapshot buffer. Read the contents for more\n"
+	"\t\t\t  information\n"
 #endif
 #ifdef CONFIG_STACK_TRACER
 	"  stack_trace\t\t- Shows the max stack trace when active\n"
 	"  stack_max_size\t- Shows current max stack size that was traced\n"
-	"\t\t\t  Write into this file to reset the max size (trigger a new trace)\n"
+	"\t\t\t  Write into this file to reset the max size (trigger a\n"
+	"\t\t\t  new trace)\n"
 #ifdef CONFIG_DYNAMIC_FTRACE
-	"  stack_trace_filter\t- Like set_ftrace_filter but limits what stack_trace traces\n"
+	"  stack_trace_filter\t- Like set_ftrace_filter but limits what stack_trace\n"
+	"\t\t\t  traces\n"
 #endif
 #endif /* CONFIG_STACK_TRACER */
+	"  events/\t\t- Directory containing all trace event subsystems:\n"
+	"      enable\t\t- Write 0/1 to enable/disable tracing of all events\n"
+	"  events/<system>/\t- Directory containing all trace events for <system>:\n"
+	"      enable\t\t- Write 0/1 to enable/disable tracing of all <system>\n"
+	"\t\t\t  events\n"
+	"      filter\t\t- If set, only events passing filter are traced\n"
+	"  events/<system>/<event>/\t- Directory containing control files for\n"
+	"\t\t\t  <event>:\n"
+	"      enable\t\t- Write 0/1 to enable/disable tracing of <event>\n"
+	"      filter\t\t- If set, only events passing filter are traced\n"
+	"      trigger\t\t- If set, a command to perform when event is hit\n"
+	"\t    Format: <trigger>[:count][if <filter>]\n"
+	"\t   trigger: traceon, traceoff\n"
+	"\t            enable_event:<system>:<event>\n"
+	"\t            disable_event:<system>:<event>\n"
+#ifdef CONFIG_STACKTRACE
+	"\t\t    stacktrace\n"
+#endif
+#ifdef CONFIG_TRACER_SNAPSHOT
+	"\t\t    snapshot\n"
+#endif
+	"\t   example: echo traceoff > events/block/block_unplug/trigger\n"
+	"\t            echo traceoff:3 > events/block/block_unplug/trigger\n"
+	"\t            echo 'enable_event:kmem:kmalloc:3 if nr_rq > 1' > \\\n"
+	"\t                  events/block/block_unplug/trigger\n"
+	"\t   The first disables tracing every time block_unplug is hit.\n"
+	"\t   The second disables tracing the first 3 times block_unplug is hit.\n"
+	"\t   The third enables the kmalloc event the first 3 times block_unplug\n"
+	"\t     is hit and has value of greater than 1 for the 'nr_rq' event field.\n"
+	"\t   Like function triggers, the counter is only decremented if it\n"
+	"\t    enabled or disabled tracing.\n"
+	"\t   To remove a trigger without a count:\n"
+	"\t     echo '!<trigger> > <system>/<event>/trigger\n"
+	"\t   To remove a trigger with a count:\n"
+	"\t     echo '!<trigger>:0 > <system>/<event>/trigger\n"
+	"\t   Filters can be ignored when removing a trigger.\n"
 ;
 
 static ssize_t
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