The function register_tracer() is only used by kernel core code,
that never needs to remove the tracer. As trace_events have become
the main way to add new tracing to the kernel, the need to
unregister a tracer has diminished. Remove the unused function
unregister_tracer(). If a need arises where we need it, then we
can always add it back.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Because the "tsc" clock isn't in nanoseconds, the ring buffer must be
reset when changing clocks so that incomparable timestamps don't end up
in the same trace.

Tested: Confirmed switching clocks resets the trace buffer.

Google-Bug-Id: 6980623
Link: http://lkml.kernel.org/r/1349998076-15495-3-git-send-email-dhsharp@google.com

Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: NDavid Sharp <dhsharp@google.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Whenever an event is registered, the comm of tasks are saved at
every task switch instead of saving them at every event. But if
an event isn't executed much, the comm cache will be filled up
by tasks that did not record the event and you lose out on the comms
that did.

Here's an example, if you enable the following events:

echo 1 > /debug/tracing/events/kvm/kvm_cr/enable
echo 1 > /debug/tracing/events/net/net_dev_xmit/enable

Note, there's no kvm running on this machine so the first event will
never be triggered, but because it is enabled, the storing of comms
will continue. If we now disable the network event:

echo 0 > /debug/tracing/events/net/net_dev_xmit/enable

and look at the trace:

cat /debug/tracing/trace
            sshd-2672  [001] ..s2   375.731616: net_dev_xmit: dev=eth0 skbaddr=ffff88005cbb6de0 len=242 rc=0
            sshd-2672  [001] ..s1   375.731617: net_dev_xmit: dev=br0 skbaddr=ffff88005cbb6de0 len=242 rc=0
            sshd-2672  [001] ..s2   375.859356: net_dev_xmit: dev=eth0 skbaddr=ffff88005cbb6de0 len=242 rc=0
            sshd-2672  [001] ..s1   375.859357: net_dev_xmit: dev=br0 skbaddr=ffff88005cbb6de0 len=242 rc=0
            sshd-2672  [001] ..s2   375.947351: net_dev_xmit: dev=eth0 skbaddr=ffff88005cbb6de0 len=242 rc=0
            sshd-2672  [001] ..s1   375.947352: net_dev_xmit: dev=br0 skbaddr=ffff88005cbb6de0 len=242 rc=0
            sshd-2672  [001] ..s2   376.035383: net_dev_xmit: dev=eth0 skbaddr=ffff88005cbb6de0 len=242 rc=0
            sshd-2672  [001] ..s1   376.035383: net_dev_xmit: dev=br0 skbaddr=ffff88005cbb6de0 len=242 rc=0
            sshd-2672  [001] ..s2   377.563806: net_dev_xmit: dev=eth0 skbaddr=ffff88005cbb6de0 len=226 rc=0
            sshd-2672  [001] ..s1   377.563807: net_dev_xmit: dev=br0 skbaddr=ffff88005cbb6de0 len=226 rc=0
            sshd-2672  [001] ..s2   377.563834: net_dev_xmit: dev=eth0 skbaddr=ffff88005cbb6be0 len=114 rc=0
            sshd-2672  [001] ..s1   377.563842: net_dev_xmit: dev=br0 skbaddr=ffff88005cbb6be0 len=114 rc=0

We see that process 2672 which triggered the events has the comm "sshd".
But if we run hackbench for a bit and look again:

cat /debug/tracing/trace
           <...>-2672  [001] ..s2   375.731616: net_dev_xmit: dev=eth0 skbaddr=ffff88005cbb6de0 len=242 rc=0
           <...>-2672  [001] ..s1   375.731617: net_dev_xmit: dev=br0 skbaddr=ffff88005cbb6de0 len=242 rc=0
           <...>-2672  [001] ..s2   375.859356: net_dev_xmit: dev=eth0 skbaddr=ffff88005cbb6de0 len=242 rc=0
           <...>-2672  [001] ..s1   375.859357: net_dev_xmit: dev=br0 skbaddr=ffff88005cbb6de0 len=242 rc=0
           <...>-2672  [001] ..s2   375.947351: net_dev_xmit: dev=eth0 skbaddr=ffff88005cbb6de0 len=242 rc=0
           <...>-2672  [001] ..s1   375.947352: net_dev_xmit: dev=br0 skbaddr=ffff88005cbb6de0 len=242 rc=0
           <...>-2672  [001] ..s2   376.035383: net_dev_xmit: dev=eth0 skbaddr=ffff88005cbb6de0 len=242 rc=0
           <...>-2672  [001] ..s1   376.035383: net_dev_xmit: dev=br0 skbaddr=ffff88005cbb6de0 len=242 rc=0
           <...>-2672  [001] ..s2   377.563806: net_dev_xmit: dev=eth0 skbaddr=ffff88005cbb6de0 len=226 rc=0
           <...>-2672  [001] ..s1   377.563807: net_dev_xmit: dev=br0 skbaddr=ffff88005cbb6de0 len=226 rc=0
           <...>-2672  [001] ..s2   377.563834: net_dev_xmit: dev=eth0 skbaddr=ffff88005cbb6be0 len=114 rc=0
           <...>-2672  [001] ..s1   377.563842: net_dev_xmit: dev=br0 skbaddr=ffff88005cbb6be0 len=114 rc=0

The stored "sshd" comm has been flushed out and we get a useless "<...>".

But by only storing comms after a trace event occurred, we can run
hackbench all day and still get the same output.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

If comm recording is not enabled when trace_printk() is used then
you just get this type of output:

[ adding trace_printk("hello! %d", irq); in do_IRQ ]

           <...>-2843  [001] d.h.    80.812300: do_IRQ: hello! 14
           <...>-2734  [002] d.h2    80.824664: do_IRQ: hello! 14
           <...>-2713  [003] d.h.    80.829971: do_IRQ: hello! 14
           <...>-2814  [000] d.h.    80.833026: do_IRQ: hello! 14

By enabling the comm recorder when trace_printk is enabled:

       hackbench-6715  [001] d.h.   193.233776: do_IRQ: hello! 21
            sshd-2659  [001] d.h.   193.665862: do_IRQ: hello! 21
          <idle>-0     [001] d.h1   193.665996: do_IRQ: hello! 21
Suggested-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Since tracing is not used by 99% of Linux users, even though tracing
may be configured in, it does not make sense to allocate 1.4 Megs
per CPU for the ring buffers if they are not used. Thus, on boot up
the ring buffers are set to a minimal size until something needs the
and they are expanded.

This works well for events and tracers (function, etc), but for the
asynchronous use of trace_printk() which can write to the ring buffer
at any time, does not expand the buffers.

On boot up a check is made to see if any trace_printk() is used to
see if the trace_printk() temp buffer pages should be allocated. This
same code can be used to expand the buffers as well.
Suggested-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The existing 'overrun' counter is incremented when the ring
buffer wraps around, with overflow on (the default). We wanted
a way to count requests lost from the buffer filling up with
overflow off, too. I decided to add a new counter instead
of retro-fitting the existing one because it seems like a
different statistic to count conceptually, and also because
of how the code was structured.

Link: http://lkml.kernel.org/r/1310765038-26399-1-git-send-email-slavapestov@google.comSigned-off-by: NSlava Pestov <slavapestov@google.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

 * remove old string conversions with kstrto*

Link: http://lkml.kernel.org/r/20120926200838.GC1244@0x90.atSigned-off-by: NDaniel Walter <sahne@0x90.at>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Use generic steal operation on pipe buffer to allow stealing
ring buffer's read page from pipe buffer.

Note that this could reduce the performance of splice on the
splice_write side operation without affinity setting.
Since the ring buffer's read pages are allocated on the
tracing-node, but the splice user does not always execute
splice write side operation on the same node. In this case,
the page will be accessed from the another node.
Thus, it is strongly recommended to assign the splicing
thread to corresponding node.
Signed-off-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

In our application, we have trace markers spread through user-space.
We have markers in GL, X, etc. These are super handy for Chrome's
about:tracing feature (Chrome + system + kernel trace view), but
can be very distracting when you're trying to debug a kernel issue.

I normally, use "grep -v tracing_mark_write" but it would be nice
if I could just temporarily disable markers all together.

Link: http://lkml.kernel.org/r/1347066739-26285-1-git-send-email-msb@chromium.org

CC: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NMandeep Singh Baines <msb@chromium.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

- When tracing capture the kuid.
- When displaying the data to user space convert the kuid into the
  user namespace of the process that opened the report file.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>

Fix some typos in kernel/trace.

Link: http://lkml.kernel.org/r/1343887320.2228.9.camel@louis-ThinkPad-T410Signed-off-by: NWang Tianhong <wangthbj@linux.vnet.ibm.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

If tracer->init() fails, current code will leave current_tracer pointing
to an unusable tracer, which at best makes 'current_tracer' report
inaccurate value.

Fix the issue by pointing current_tracer to nop tracer, and only update
current_tracer with the new one after all the initialization succeeds.
Signed-off-by: NAnton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Clean up and return -ENOMEM on if the kzalloc() fails.

This also prevents a potential crash, as the pointer that failed to
allocate would be later used.

Link: http://lkml.kernel.org/r/20120711063507.GF11812@elgon.mountain

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Replace the NR_CPUS array of buffer_iter from the trace_iterator
with an allocated array. This will just create an array of
possible CPUS instead of the max number specified.

The use of NR_CPUS in that array caused allocation failures for
machines that were tight on memory. This did not cause any failures
to the system itself (no crashes), but caused unnecessary failures
for reading the trace files.

Added a helper function called 'trace_buffer_iter()' that returns
the buffer_iter item or NULL if it is not defined or the array was
not allocated. Some routines do not require the array
(tracing_open_pipe() for one).
Reported-by: NDave Jones <davej@redhat.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Add a WARN_ON() output on test failures so that they are easier to detect
in automated tests. Although, the WARN_ON() will not print if the test
causes the system to crash, obviously.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Dave Jones reported a kernel BUG at mm/slub.c:3474! triggered
by splice_shrink_spd() called from vmsplice_to_pipe()

commit 35f3d14d (pipe: add support for shrinking and growing pipes)
added capability to adjust pipe->buffers.

Problem is some paths don't hold pipe mutex and assume pipe->buffers
doesn't change for their duration.

Fix this by adding nr_pages_max field in struct splice_pipe_desc, and
use it in place of pipe->buffers where appropriate.

splice_shrink_spd() loses its struct pipe_inode_info argument.
Reported-by: NDave Jones <davej@redhat.com>
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Tom Herbert <therbert@google.com>
Cc: stable <stable@vger.kernel.org> # 2.6.35
Tested-by: NDave Jones <davej@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

A recent update to have tracing_on/off() only affect the ftrace ring
buffers instead of all ring buffers had a cut and paste error.
The tracing_off() did the exact same thing as tracing_on() and
would not actually turn off tracing. Unfortunately, tracing_off()
is more important to be working than tracing_on() as this is a key
development tool, as it lets the developer turn off tracing as soon
as a problem is discovered. It is also used by panic and oops code.

This bug also breaks the 'echo func:traceoff > set_ftrace_filter'

Cc: <stable@vger.kernel.org> # 3.4
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The BKL is gone, these annotations are useless.

Link: http://lkml.kernel.org/r/1320654202-4433-1-git-send-email-richard@nod.atSigned-off-by: NRichard Weinberger <richard@nod.at>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Make sure that the state of buffer_size_kb is initialized correctly and
returns actual size of the ring buffer.

Link: http://lkml.kernel.org/r/1336066834-1673-1-git-send-email-vnagarnaik@google.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Laurent Chavey <chavey@google.com>
Cc: Justin Teravest <teravest@google.com>
Cc: David Sharp <dhsharp@google.com>
Signed-off-by: NVaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

According to Documentation/trace/ftrace.txt:

tracing_cpumask:

        This is a mask that lets the user only trace
        on specified CPUS. The format is a hex string
        representing the CPUS.

The tracing_cpumask currently doesn't affect the tracing state of
per-CPU ring buffers.

This patch enables/disables CPU recording as its corresponding bit in
tracing_cpumask is set/unset.

Link: http://lkml.kernel.org/r/1336096792-25373-3-git-send-email-vnagarnaik@google.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Laurent Chavey <chavey@google.com>
Cc: Justin Teravest <teravest@google.com>
Cc: David Sharp <dhsharp@google.com>
Signed-off-by: NVaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

If tracing_dentry_percpu() failed, tracing_init_debugfs_percpu()
will try to create each cpu directories on debugfs' root directory
as d_percpu is NULL.

Link: http://lkml.kernel.org/r/1335143517-2285-1-git-send-email-namhyung.kim@lge.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: NNamhyung Kim <namhyung.kim@lge.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

This patch adds the capability to remove pages from a ring buffer
without destroying any existing data in it.

This is done by removing the pages after the tail page. This makes sure
that first all the empty pages in the ring buffer are removed. If the
head page is one in the list of pages to be removed, then the page after
the removed ones is made the head page. This removes the oldest data
from the ring buffer and keeps the latest data around to be read.

To do this in a non-racey manner, tracing is stopped for a very short
time while the pages to be removed are identified and unlinked from the
ring buffer. The pages are freed after the tracing is restarted to
minimize the time needed to stop tracing.

The context in which the pages from the per-cpu ring buffer are removed
runs on the respective CPU. This minimizes the events not traced to only
NMI trace contexts.

Link: http://lkml.kernel.org/r/1336096792-25373-1-git-send-email-vnagarnaik@google.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Laurent Chavey <chavey@google.com>
Cc: Justin Teravest <teravest@google.com>
Cc: David Sharp <dhsharp@google.com>
Signed-off-by: NVaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

On gcc 4.5 the function tracing_mark_write() would give a warning
of page2 being uninitialized. This is due to a bug in gcc because
the logic prevents page2 from being used uninitialized, and
gcc 4.6+ does not complain (correctly).

Instead of adding a "unitialized" around page2, which could show
a bug later on, I combined page1 and page2 into an array map_pages[].
This binds the two and the two are modified according to nr_pages
(what gcc 4.5 seems to ignore). This no longer gives a warning with
gcc 4.5 nor with gcc 4.6.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The ftrace_disable_cpu() and ftrace_enable_cpu() functions were
needed back before the ring buffer was lockless. Now that the
ring buffer is lockless (and has been for some time), these functions
serve no purpose, and unnecessarily slow down operations of the tracer.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

It's appropriate to use __seq_open_private interface to open
some of trace seq files, because it covers all steps we are
duplicating in tracing code - zallocating the iterator and
setting it as seq_file's private.

Using this for following files:
  trace
  available_filter_functions
  enabled_functions

Link: http://lkml.kernel.org/r/1335342219-2782-5-git-send-email-jolsa@redhat.comSigned-off-by: NJiri Olsa <jolsa@redhat.com>

[
 Fixed warnings for:
   kernel/trace/trace.c: In function '__tracing_open':
   kernel/trace/trace.c:2418:11: warning: unused variable 'ret' [-Wunused-variable]
   kernel/trace/trace.c:2417:19: warning: unused variable 'm' [-Wunused-variable]
]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Add a debugfs entry under per_cpu/ folder for each cpu called
buffer_size_kb to control the ring buffer size for each CPU
independently.

If the global file buffer_size_kb is used to set size, the individual
ring buffers will be adjusted to the given size. The buffer_size_kb will
report the common size to maintain backward compatibility.

If the buffer_size_kb file under the per_cpu/ directory is used to
change buffer size for a specific CPU, only the size of the respective
ring buffer is updated. When tracing/buffer_size_kb is read, it reports
'X' to indicate that sizes of per_cpu ring buffers are not equivalent.

Link: http://lkml.kernel.org/r/1328212844-11889-1-git-send-email-vnagarnaik@google.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Cc: Justin Teravest <teravest@google.com>
Signed-off-by: NVaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

memcpy() returns a pointer to "bug".  Hopefully, it's not NULL here or
we would already have Oopsed.

Link: http://lkml.kernel.org/r/20120420063145.GA22649@elgon.mountain

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Currently, trace_printk() uses a single buffer to write into
to calculate the size and format needed to save the trace. To
do this safely in an SMP environment, a spin_lock() is taken
to only allow one writer at a time to the buffer. But this could
also affect what is being traced, and add synchronization that
would not be there otherwise.

Ideally, using percpu buffers would be useful, but since trace_printk()
is only used in development, having per cpu buffers for something
never used is a waste of space. Thus, the use of the trace_bprintk()
format section is changed to be used for static fmts as well as dynamic ones.
Then at boot up, we can check if the section that holds the trace_printk
formats is non-empty, and if it does contain something, then we
know a trace_printk() has been added to the kernel. At this time
the trace_printk per cpu buffers are allocated. A check is also
done at module load time in case a module is added that contains a
trace_printk().

Once the buffers are allocated, they are never freed. If you use
a trace_printk() then you should know what you are doing.

A buffer is made for each type of context:

  normal
  softirq
  irq
  nmi

The context is checked and the appropriate buffer is used.
This allows for totally lockless usage of trace_printk(),
and they no longer even disable interrupts.
Requested-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The change to make tracing_on affect only the ftrace ring buffer, caused
a bug where it wont affect any ring buffer. The problem was that the buffer
of the trace_array was passed to the write function and not the trace array
itself.

The trace_array can change the buffer when running a latency tracer. If this
happens, then the buffer being disabled may not be the buffer currently used
by ftrace. This will cause the tracing_on file to become useless.

The simple fix is to pass the trace_array to the write function instead of
the buffer. Then the actual buffer may be changed.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

When reading the trace file, the records of each of the per_cpu buffers
are examined to find the next event to print out. At the point of looking
at the event, the size of the event is recorded. But if the first event is
chosen, the other events in the other CPU buffers will reset the event size
that is stored in the iterator descriptor, causing the event size passed to
the output functions to be incorrect.

In most cases this is not a problem, but for the case of stack traces, it
is. With the change to the stack tracing to record a dynamic number of
back traces, the output depends on the size of the entry instead of the
fixed 8 back traces. When the entry size is not correct, the back traces
would not be fully printed.

Note, reading from the per-cpu trace files were not affected.
Reported-by: NThomas Gleixner <tglx@linutronix.de>
Tested-by: NThomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

As ftrace_dump() (called by ftrace_dump_on_oops) disables interrupts
as it dumps its output to the console, it can keep interrupts disabled
for long periods of time. This is likely to trigger the NMI watchdog,
and it can disrupt the output of critical data.

Add a touch_nmi_watchdog() to each event that is written to the screen
to keep the NMI watchdog from affecting the output.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

As the ring-buffer code is being used by other facilities in the
kernel, having tracing_on file disable *all* buffers is not a desired
affect. It should only disable the ftrace buffers that are being used.

Move the code into the trace.c file and use the buffer disabling
for tracing_on() and tracing_off(). This way only the ftrace buffers
will be affected by them and other kernel utilities will not be
confused to why their output suddenly stopped.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Actually, sched_switch function tracer is merged into wakeup/wakeup_rt
Update 'mini-HOWTO' for ftrace(Kernel function tracer).
If we want to trace "sched:sched_switch" to trace sched_switch func,
We may utilize event option.(e.g: trace-cmd list -e | grep sched)
This patch is based on Linux-3.3.rc2-SMP-PREEMPT

Link: http://lkml.kernel.org/r/1328695537-15081-1-git-send-email-geunsik.lim@gmail.com

Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NGeunsik Lim <geunsik.lim@samsung.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Add an EXPORT_SYMBOL_GPL() so that rcutorture can dump the trace buffer
upon detection of an RCU error.
Signed-off-by: NPaul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

Knowing the number of event entries in the ring buffer compared
to the total number that were written is useful information. The
latency format gives this information and there's no reason that the
default format does not.

This information is now added to the default header, along with the
number of online CPUs:

 # tracer: nop
 #
 # entries-in-buffer/entries-written: 159836/64690869   #P:4
 #
 #                              _-----=> irqs-off
 #                             / _----=> need-resched
 #                            | / _---=> hardirq/softirq
 #                            || / _--=> preempt-depth
 #                            ||| /     delay
 #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
 #              | |       |   ||||       |         |
           <idle>-0     [000] ...2    49.442971: local_touch_nmi <-cpu_idle
           <idle>-0     [000] d..2    49.442973: enter_idle <-cpu_idle
           <idle>-0     [000] d..2    49.442974: atomic_notifier_call_chain <-enter_idle
           <idle>-0     [000] d..2    49.442976: __atomic_notifier_call_chain <-atomic_notifier

The above shows that the trace contains 159836 entries, but
64690869 were written. One could figure out that there were
64531033 entries that were dropped.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

People keep asking how to get the preempt count, irq, and need resched info
and we keep telling them to enable the latency format. Some developers think
that traces without this info is completely useless, and for a lot of tasks
it is useless.

The first option was to enable the latency trace as the default format, but
the header for the latency format is pretty useless for most tracers and
it also does the timestamp in straight microseconds from the time the trace
started. This is sometimes more difficult to read as the default trace is
seconds from the start of boot up.

Latency format:

 # tracer: nop
 #
 # nop latency trace v1.1.5 on 3.2.0-rc1-test+
 # --------------------------------------------------------------------
 # latency: 0 us, #159771/64234230, CPU#1 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:4)
 #    -----------------
 #    | task: -0 (uid:0 nice:0 policy:0 rt_prio:0)
 #    -----------------
 #
 #                  _------=> CPU#
 #                 / _-----=> irqs-off
 #                | / _----=> need-resched
 #                || / _---=> hardirq/softirq
 #                ||| / _--=> preempt-depth
 #                |||| /     delay
 #  cmd     pid   ||||| time  |   caller
 #     \   /      |||||  \    |   /
 migratio-6       0...2 41778231us+: rcu_note_context_switch <-__schedule
 migratio-6       0...2 41778233us : trace_rcu_utilization <-rcu_note_context_switch
 migratio-6       0...2 41778235us+: rcu_sched_qs <-rcu_note_context_switch
 migratio-6       0d..2 41778236us+: rcu_preempt_qs <-rcu_note_context_switch
 migratio-6       0...2 41778238us : trace_rcu_utilization <-rcu_note_context_switch
 migratio-6       0...2 41778239us+: debug_lockdep_rcu_enabled <-__schedule

default format:

 # tracer: nop
 #
 #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
 #              | |       |          |         |
      migration/0-6     [000]    50.025810: rcu_note_context_switch <-__schedule
      migration/0-6     [000]    50.025812: trace_rcu_utilization <-rcu_note_context_switch
      migration/0-6     [000]    50.025813: rcu_sched_qs <-rcu_note_context_switch
      migration/0-6     [000]    50.025815: rcu_preempt_qs <-rcu_note_context_switch
      migration/0-6     [000]    50.025817: trace_rcu_utilization <-rcu_note_context_switch
      migration/0-6     [000]    50.025818: debug_lockdep_rcu_enabled <-__schedule
      migration/0-6     [000]    50.025820: debug_lockdep_rcu_enabled <-__schedule

The latency format header has latency information that is pretty meaningless
for most tracers. Although some of the header is useful, and we can add that
later to the default format as well.

What is really useful with the latency format is the irqs-off, need-resched
hard/softirq context and the preempt count.

This commit adds the option irq-info which is on by default that adds this
information:

 # tracer: nop
 #
 #                              _-----=> irqs-off
 #                             / _----=> need-resched
 #                            | / _---=> hardirq/softirq
 #                            || / _--=> preempt-depth
 #                            ||| /     delay
 #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
 #              | |       |   ||||       |         |
           <idle>-0     [000] d..2    49.309305: cpuidle_get_driver <-cpuidle_idle_call
           <idle>-0     [000] d..2    49.309307: mwait_idle <-cpu_idle
           <idle>-0     [000] d..2    49.309309: need_resched <-mwait_idle
           <idle>-0     [000] d..2    49.309310: test_ti_thread_flag <-need_resched
           <idle>-0     [000] d..2    49.309312: trace_power_start.constprop.13 <-mwait_idle
           <idle>-0     [000] d..2    49.309313: trace_cpu_idle <-mwait_idle
           <idle>-0     [000] d..2    49.309315: need_resched <-mwait_idle

If a user wants the old format, they can disable the 'irq-info' option:

 # tracer: nop
 #
 #           TASK-PID   CPU#      TIMESTAMP  FUNCTION
 #              | |       |          |         |
           <idle>-0     [000]     49.309305: cpuidle_get_driver <-cpuidle_idle_call
           <idle>-0     [000]     49.309307: mwait_idle <-cpu_idle
           <idle>-0     [000]     49.309309: need_resched <-mwait_idle
           <idle>-0     [000]     49.309310: test_ti_thread_flag <-need_resched
           <idle>-0     [000]     49.309312: trace_power_start.constprop.13 <-mwait_idle
           <idle>-0     [000]     49.309313: trace_cpu_idle <-mwait_idle
           <idle>-0     [000]     49.309315: need_resched <-mwait_idle
Requested-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

In case the the graph tracer (CONFIG_FUNCTION_GRAPH_TRACER) or even the
function tracer (CONFIG_FUNCTION_TRACER) are not set, the latency tracers
do not display proper latency header.

The involved/fixed latency tracers are:
        wakeup_rt
        wakeup
        preemptirqsoff
        preemptoff
        irqsoff

The patch adds proper handling of tracer configuration options for latency
tracers, and displaying correct header info accordingly.

* The current output (for wakeup tracer) with both graph and function
  tracers disabled is:

  # tracer: wakeup
  #
    <idle>-0       0d.h5    1us+:      0:120:R   + [000]     7:  0:R watchdog/0
    <idle>-0       0d.h5    3us+: ttwu_do_activate.clone.1 <-try_to_wake_up
    ...

* The fixed output is:

  # tracer: wakeup
  #
  # wakeup latency trace v1.1.5 on 3.1.0-tip+
  # --------------------------------------------------------------------
  # latency: 55 us, #4/4, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2)
  #    -----------------
  #    | task: migration/0-6 (uid:0 nice:0 policy:1 rt_prio:99)
  #    -----------------
  #
  #                  _------=> CPU#
  #                 / _-----=> irqs-off
  #                | / _----=> need-resched
  #                || / _---=> hardirq/softirq
  #                ||| / _--=> preempt-depth
  #                |||| /     delay
  #  cmd     pid   ||||| time  |   caller
  #     \   /      |||||  \    |   /
       cat-1129    0d..4    1us :   1129:120:R   + [000]     6:  0:R migration/0
       cat-1129    0d..4    2us+: ttwu_do_activate.clone.1 <-try_to_wake_up

* The current output (for wakeup tracer) with only function
  tracer enabled is:

  # tracer: wakeup
  #
       cat-1140    0d..4    1us+:   1140:120:R   + [000]     6:  0:R migration/0
       cat-1140    0d..4    2us : ttwu_do_activate.clone.1 <-try_to_wake_up

* The fixed output is:
  # tracer: wakeup
  #
  # wakeup latency trace v1.1.5 on 3.1.0-tip+
  # --------------------------------------------------------------------
  # latency: 207 us, #109/109, CPU#1 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2)
  #    -----------------
  #    | task: watchdog/1-12 (uid:0 nice:0 policy:1 rt_prio:99)
  #    -----------------
  #
  #                  _------=> CPU#
  #                 / _-----=> irqs-off
  #                | / _----=> need-resched
  #                || / _---=> hardirq/softirq
  #                ||| / _--=> preempt-depth
  #                |||| /     delay
  #  cmd     pid   ||||| time  |   caller
  #     \   /      |||||  \    |   /
    <idle>-0       1d.h5    1us+:      0:120:R   + [001]    12:  0:R watchdog/1
    <idle>-0       1d.h5    3us : ttwu_do_activate.clone.1 <-try_to_wake_up

Link: http://lkml.kernel.org/r/20111107150849.GE1807@m.brq.redhat.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: NJiri Olsa <jolsa@redhat.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The trace_pipe_raw handler holds a cached page from the time the file
is opened to the time it is closed. The cached page is used to handle
the case of the user space buffer being smaller than what was read from
the ring buffer. The left over buffer is held in the cache so that the
next read will continue where the data left off.

After EOF is returned (no more data in the buffer), the index of
the cached page is set to zero. If a user app reads the page again
after EOF, the check in the buffer will see that the cached page
is less than page size and will return the cached page again. This
will cause reading the trace_pipe_raw again after EOF to return
duplicate data, making the output look like the time went backwards
but instead data is just repeated.

The fix is to not reset the index right after all data is read
from the cache, but to reset it after all data is read and more
data exists in the ring buffer.

Cc: stable <stable@kernel.org>
Reported-by: NJeremy Eder <jeder@redhat.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

tracing_enabled option is deprecated.
To start/stop tracing, write to /sys/kernel/debug/tracing/tracing_on
without tracing_enabled. This patch is based on Linux 3.1.0-rc1
Signed-off-by: NGeunsik Lim <geunsik.lim@samsung.com>
Link: http://lkml.kernel.org/r/1313127022-23830-1-git-send-email-leemgs1@gmail.comSigned-off-by: NSteven Rostedt <rostedt@goodmis.org>