The irqsoff, preemptoff and preemptirqsoff tracers can now be used by
instances. But they may only be used by one instance at a time (including
the top level directory). This allows multiple tracers to run while the
irqsoff (and friends) tracer is running simultaneously.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

In preparation for letting the latency tracers be used by instances,
remove the global tracing_max_latency variable and add a max_latency
field to the trace_array that the latency tracers will now use.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Instead of having a list of global functions that are called,
as only one global function is allow to be enabled at a time, there's
no reason to have a list.

Instead, simply have all the users of the global ops, use the global ops
directly, instead of registering their own ftrace_ops. Just switch what
function is used before enabling the function tracer.

This removes a lot of code as well as the complexity involved with it.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Pull tracing updates from Steven Rostedt:
 "Most of the changes were largely clean ups, and some documentation.
  But there were a few features that were added:

  Uprobes now work with event triggers and multi buffers and have
  support under ftrace and perf.

  The big feature is that the function tracer can now be used within the
  multi buffer instances.  That is, you can now trace some functions in
  one buffer, others in another buffer, all functions in a third buffer
  and so on.  They are basically agnostic from each other.  This only
  works for the function tracer and not for the function graph trace,
  although you can have the function graph tracer running in the top
  level buffer (or any tracer for that matter) and have different
  function tracing going on in the sub buffers"

* tag 'trace-3.15' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (45 commits)
  tracing: Add BUG_ON when stack end location is over written
  tracepoint: Remove unused API functions
  Revert "tracing: Move event storage for array from macro to standalone function"
  ftrace: Constify ftrace_text_reserved
  tracepoints: API doc update to tracepoint_probe_register() return value
  tracepoints: API doc update to data argument
  ftrace: Fix compilation warning about control_ops_free
  ftrace/x86: BUG when ftrace recovery fails
  ftrace: Warn on error when modifying ftrace function
  ftrace: Remove freelist from struct dyn_ftrace
  ftrace: Do not pass data to ftrace_dyn_arch_init
  ftrace: Pass retval through return in ftrace_dyn_arch_init()
  ftrace: Inline the code from ftrace_dyn_table_alloc()
  ftrace: Cleanup of global variables ftrace_new_pgs and ftrace_update_cnt
  tracing: Evaluate len expression only once in __dynamic_array macro
  tracing: Correctly expand len expressions from __dynamic_array macro
  tracing/module: Replace include of tracepoint.h with jump_label.h in module.h
  tracing: Fix event header migrate.h to include tracepoint.h
  tracing: Fix event header writeback.h to include tracepoint.h
  tracing: Warn if a tracepoint is not set via debugfs
  ...

As options (flags) may affect instances instead of being global
the flag_changed() callbacks need to receive the trace_array descriptor
of the instance they will be modifying.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

As options (flags) may affect instances instead of being global
the set_flag() callbacks need to receive the trace_array descriptor
of the instance they will be modifying.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

These functions are called from assembler, and thus need to be
__visible.

Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1391845930-28580-12-git-send-email-ak@linux.intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

If the ring buffer is disabled and the irqsoff tracer records a trace it
will clear out its buffer and lose the data it had previously recorded.

Currently there's a callback when writing to the tracing_of file, but if
tracing is disabled via the function tracer trigger, it will not inform
the irqsoff tracer to stop recording.

By using the "mirror" flag (buffer_disabled) in the trace_array, that keeps
track of the status of the trace_array's buffer, it gives the irqsoff
tracer a fast way to know if it should record a new trace or not.
The flag may be a little behind the real state of the buffer, but it
should not affect the trace too much. It's more important for the irqsoff
tracer to be fast.

Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Currently, the only way to stop the latency tracers from doing function
tracing is to fully disable the function tracer from the proc file
system:

  echo 0 > /proc/sys/kernel/ftrace_enabled

This is a big hammer approach as it disables function tracing for
all users. This includes kprobes, perf, stack tracer, etc.

Instead, create a function-trace option that the latency tracers can
check to determine if it should enable function tracing or not.
This option can be set or cleared even while the tracer is active
and the tracers will disable or enable function tracing depending
on how the option was set.

Instead of using the proc file, disable latency function tracing with

  echo 0 > /debug/tracing/options/function-trace

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Currently, the way the latency tracers and snapshot feature works
is to have a separate trace_array called "max_tr" that holds the
snapshot buffer. For latency tracers, this snapshot buffer is used
to swap the running buffer with this buffer to save the current max
latency.

The only items needed for the max_tr is really just a copy of the buffer
itself, the per_cpu data pointers, the time_start timestamp that states
when the max latency was triggered, and the cpu that the max latency
was triggered on. All other fields in trace_array are unused by the
max_tr, making the max_tr mostly bloat.

This change removes the max_tr completely, and adds a new structure
called trace_buffer, that holds the buffer pointer, the per_cpu data
pointers, the time_start timestamp, and the cpu where the latency occurred.

The trace_array, now has two trace_buffers, one for the normal trace and
one for the max trace or snapshot. By doing this, not only do we remove
the bloat from the max_trace but the instances of traces can now use
their own snapshot feature and not have just the top level global_trace have
the snapshot feature and latency tracers for itself.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>