Commit 2455f0e1 authored by Ross Zwisler's avatar Ross Zwisler Committed by Steven Rostedt (Google)
Browse files

tracing: Always use canonical ftrace path 

The canonical location for the tracefs filesystem is at /sys/kernel/tracing.

But, from Documentation/trace/ftrace.rst:

  Before 4.1, all ftrace tracing control files were within the debugfs
  file system, which is typically located at /sys/kernel/debug/tracing.
  For backward compatibility, when mounting the debugfs file system,
  the tracefs file system will be automatically mounted at:

  /sys/kernel/debug/tracing

Many comments and Kconfig help messages in the tracing code still refer
to this older debugfs path, so let's update them to avoid confusion.

Link: https://lore.kernel.org/linux-trace-kernel/20230215223350.2658616-2-zwisler@google.com



Acked-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: default avatarMukesh Ojha <quic_mojha@quicinc.com>
Signed-off-by: default avatarRoss Zwisler <zwisler@google.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent d8f0ae3e

include/linux/kernel.h

+1 −1
Original line number Diff line number Diff line
@@ -297,7 +297,7 @@ bool mac_pton(const char *s, u8 *mac); 
 *

 * Use tracing_on/tracing_off when you want to quickly turn on or off

 * tracing. It simply enables or disables the recording of the trace events.

 * This also corresponds to the user space /sys/kernel/debug/tracing/tracing_on

 * This also corresponds to the user space /sys/kernel/tracing/tracing_on

 * file, which gives a means for the kernel and userspace to interact.

 * Place a tracing_off() in the kernel where you want tracing to end.

 * From user space, examine the trace, and then echo 1 > tracing_on

include/linux/tracepoint.h

+2 −2
Original line number Diff line number Diff line
@@ -471,7 +471,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) 
 *	* This is how the trace record is structured and will

 *	* be saved into the ring buffer. These are the fields

 *	* that will be exposed to user-space in

 *	* /sys/kernel/debug/tracing/events/<*>/format.

 *	* /sys/kernel/tracing/events/<*>/format.

 *	*

 *	* The declared 'local variable' is called '__entry'

 *	*
@@ -531,7 +531,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) 
 * tracepoint callback (this is used by programmatic plugins and

 * can also by used by generic instrumentation like SystemTap), and

 * it is also used to expose a structured trace record in

 * /sys/kernel/debug/tracing/events/.

 * /sys/kernel/tracing/events/.

 *

 * A set of (un)registration functions can be passed to the variant

 * TRACE_EVENT_FN to perform any (un)registration work.

kernel/trace/Kconfig

+10 −10
Original line number Diff line number Diff line
@@ -239,7 +239,7 @@ config DYNAMIC_FTRACE 
	  enabled, and the functions not enabled will not affect

	  performance of the system.



	  See the files in /sys/kernel/debug/tracing:

	  See the files in /sys/kernel/tracing:

	    available_filter_functions

	    set_ftrace_filter

	    set_ftrace_notrace
@@ -299,7 +299,7 @@ config STACK_TRACER 
	select KALLSYMS

	help

	  This special tracer records the maximum stack footprint of the

	  kernel and displays it in /sys/kernel/debug/tracing/stack_trace.

	  kernel and displays it in /sys/kernel/tracing/stack_trace.



	  This tracer works by hooking into every function call that the

	  kernel executes, and keeping a maximum stack depth value and
@@ -339,7 +339,7 @@ config IRQSOFF_TRACER 
	  disabled by default and can be runtime (re-)started

	  via:



	      echo 0 > /sys/kernel/debug/tracing/tracing_max_latency

	      echo 0 > /sys/kernel/tracing/tracing_max_latency



	  (Note that kernel size and overhead increase with this option

	  enabled. This option and the preempt-off timing option can be
@@ -363,7 +363,7 @@ config PREEMPT_TRACER 
	  disabled by default and can be runtime (re-)started

	  via:



	      echo 0 > /sys/kernel/debug/tracing/tracing_max_latency

	      echo 0 > /sys/kernel/tracing/tracing_max_latency



	  (Note that kernel size and overhead increase with this option

	  enabled. This option and the irqs-off timing option can be
@@ -515,7 +515,7 @@ config TRACER_SNAPSHOT 
	  Allow tracing users to take snapshot of the current buffer using the

	  ftrace interface, e.g.:



	      echo 1 > /sys/kernel/debug/tracing/snapshot

	      echo 1 > /sys/kernel/tracing/snapshot

	      cat snapshot



config TRACER_SNAPSHOT_PER_CPU_SWAP
@@ -527,7 +527,7 @@ config TRACER_SNAPSHOT_PER_CPU_SWAP 
	  full swap (all buffers). If this is set, then the following is

	  allowed:



	      echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot

	      echo 1 > /sys/kernel/tracing/per_cpu/cpu2/snapshot



	  After which, only the tracing buffer for CPU 2 was swapped with

	  the main tracing buffer, and the other CPU buffers remain the same.
@@ -574,7 +574,7 @@ config PROFILE_ANNOTATED_BRANCHES 
	  This tracer profiles all likely and unlikely macros

	  in the kernel. It will display the results in:



	  /sys/kernel/debug/tracing/trace_stat/branch_annotated

	  /sys/kernel/tracing/trace_stat/branch_annotated



	  Note: this will add a significant overhead; only turn this

	  on if you need to profile the system's use of these macros.
@@ -587,7 +587,7 @@ config PROFILE_ALL_BRANCHES 
	  taken in the kernel is recorded whether it hit or miss.

	  The results will be displayed in:



	  /sys/kernel/debug/tracing/trace_stat/branch_all

	  /sys/kernel/tracing/trace_stat/branch_all



	  This option also enables the likely/unlikely profiler.
@@ -638,8 +638,8 @@ config BLK_DEV_IO_TRACE 
	  Tracing also is possible using the ftrace interface, e.g.:



	    echo 1 > /sys/block/sda/sda1/trace/enable

	    echo blk > /sys/kernel/debug/tracing/current_tracer

	    cat /sys/kernel/debug/tracing/trace_pipe

	    echo blk > /sys/kernel/tracing/current_tracer

	    cat /sys/kernel/tracing/trace_pipe



	  If unsure, say N.

kernel/trace/kprobe_event_gen_test.c

+1 −1
Original line number Diff line number Diff line
@@ -21,7 +21,7 @@ 
 * Then:

 *

 * # insmod kernel/trace/kprobe_event_gen_test.ko

 * # cat /sys/kernel/debug/tracing/trace

 * # cat /sys/kernel/tracing/trace

 *

 * You should see many instances of the "gen_kprobe_test" and

 * "gen_kretprobe_test" events in the trace buffer.

kernel/trace/ring_buffer.c

+1 −1
Original line number Diff line number Diff line
@@ -2886,7 +2886,7 @@ rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer, 
		  sched_clock_stable() ? "" :

		  "If you just came from a suspend/resume,\n"

		  "please switch to the trace global clock:\n"

		  "  echo global > /sys/kernel/debug/tracing/trace_clock\n"

		  "  echo global > /sys/kernel/tracing/trace_clock\n"

		  "or add trace_clock=global to the kernel command line\n");

}