A new check was added in the ftrace function that wont trace if the CPU
trace buffer is disabled.  Unfortunately, other tracers used ftrace() to
write to the buffer after they disabled it. The new disable check makes
these calls into a nop.

This patch changes the __ftrace that is called without the check into a
new api for the other tracers to use, called "trace_function". The other
tracers use this interface instead when the trace CPU buffer is already
disabled.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

for ad-hoc tracing.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

remove idx syncing - it's expensive on SMP.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

rename and uninline now() to ftrace_now().
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

we can hold all cpu trace buffer locks at once - put each into a
separate lock class.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

This patch creates a file called trace_pipe in the tracing
debug directory. This file is a consumer of the trace buffers.
This means that reads of this file consumes the entries from
the trace buffers so that they will not be read a second time,
as contrast to the static buffers latency_trace and trace.

Reading from the trace_pipe will remove the entries from trace
and latency_trace too.

The advantage that trace_pipe has is that it can record live
traces. It will block when there is nothing in the buffer,
and read the entries as they are entered.  An EOF happens when
tracing is disabled (tracing_enabled = 0).
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Later patches will need to print the same things as the seq output
does. But those outputs will not use the seq utility. This patch
adds a buffer to the iterator, that can be used by either the
seq utility or other output.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

This patch changes the way the CPU trace buffers are handled.
Instead of always starting from the trace page head, the logic
is changed to a producer consumer logic. This allows for the
buffers to be drained while they are alive.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

fix time offset calculations and ordering, plus make code more consistent.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

factor out code and clean it up.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Allocating large buffers for the tracer may fail easily.
This patch converts the buffer from a large ordered allocation
to single pages. It uses the struct page LRU field to link the
pages together.

Later patches may also implement dynamic increasing and decreasing
of the trace buffers.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

This patch adds the latency tracer infrastructure. This patch
does not add anything that will select and turn it on, but will
be used by later patches.

If it were to be compiled, it would add the following files
to the debugfs:

 The root tracing directory:

  /debugfs/tracing/

This patch also adds the following files:

  available_tracers
     list of available tracers. Currently no tracers are
     available. Looking into this file only shows
     "none" which is used to unregister all tracers.

  current_tracer
     The trace that is currently active. Empty on start up.
     To switch to a tracer simply echo one of the tracers that
     are listed in available_tracers:

   example: (used with later patches)

      echo function > /debugfs/tracing/current_tracer

     To disable the tracer:

       echo disable > /debugfs/tracing/current_tracer

  tracing_enabled
     echoing "1" into this file starts the ftrace function tracing
      (if sysctl kernel.ftrace_enabled=1)
     echoing "0" turns it off.

  latency_trace
      This file is readonly and holds the result of the trace.

  trace
      This file outputs a easier to read version of the trace.

  iter_ctrl
      Controls the way the output of traces look.
      So far there's two controls:
        echoing in "symonly" will only show the kallsyms variables
            without the addresses (if kallsyms was configured)
        echoing in "verbose" will change the output to show
            a lot more data, but not very easy to understand by
            humans.
        echoing in "nosymonly" turns off symonly.
        echoing in "noverbose" turns off verbose.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NArnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>