On Sat, 22 Mar 2008 13:07:47 +0100
Ingo Molnar <mingo@elte.hu> wrote:

> > > i'd suggest the following: pull x86.git and sched-devel.git into a
> > > single tree [the two will combine without rejects]. Then try to add a
> > > kernel/tracing/trace_mmiotrace.c ftrace plugin. The trace_sysprof.c
> > > plugin might be a good example.
> >
> > I did this and now I have mmiotrace enabled/disabled via the tracing
> > framework (what do we call this, since ftrace is one of the tracers?).
>
> cool! could you send the patches for that? (even if they are not fully
> functional yet)

Patch attached in the end. Nice to see how much code disappeared. I tried
to mark all the features I had to break with XXX-comments.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Kconfig.debug, Makefile and testmmiotrace.c style fixes.
Use real mutex instead of mutex.
Fix failure path in register probe func.
kmmio: RCU read-locked over single stepping.
Generate mapping id's.
Make mmio-mod.c built-in and rewrite its locking.
Add debugfs file to enable/disable mmiotracing.
kmmio: use irqsave spinlocks.
Lots of cleanups in mmio-mod.c
Marker file moved from /proc into debugfs.
Call mmiotrace entrypoints directly from ioremap.c.
Signed-off-by: NPekka Paalanen <pq@iki.fi>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

kmmio.c handles the list of mmio probes with callbacks, list of traced
pages, and attaching into the page fault handler and die notifier. It
arms, traps and disarms the given pages, this is the core of mmiotrace.

mmio-mod.c is a user interface, hooking into ioremap functions and
registering the mmio probes. It also decodes the required information
from trapped mmio accesses via the pre and post callbacks in each probe.
Currently, hooking into ioremap functions works by redefining the symbols
of the target (binary) kernel module, so that it calls the traced
versions of the functions.

The most notable changes done since the last discussion are:
- kmmio.c is a built-in, not part of the module
- direct call from fault.c to kmmio.c, removing all dynamic hooks
- prepare for unregistering probes at any time
- make kmmio re-initializable and accessible to more than one user
- rewrite kmmio locking to remove all spinlocks from page fault path

Can I abuse call_rcu() like I do in kmmio.c:unregister_kmmio_probe()
or is there a better way?

The function called via call_rcu() itself calls call_rcu() again,
will this work or break? There I need a second grace period for RCU
after the first grace period for page faults.

Mmiotrace itself (mmio-mod.c) is still a module, I am going to attack
that next. At some point I will start looking into how to make mmiotrace
a tracer component of ftrace (thanks for the hint, Ingo). Ftrace should
make the user space part of mmiotracing as simple as
'cat /debug/trace/mmio > dump.txt'.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Signed-off-by: NPekka Paalanen <pq@iki.fi>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Mmiotrace is a tool for trapping memory mapped IO (MMIO) accesses within
the kernel. It is used for debugging and especially for reverse
engineering evil binary drivers.

Mmiotrace works by wrapping the ioremap family of kernel functions and
marking the returned pages as not present. Access to the IO memory
triggers a page fault, which will be handled by mmiotrace's custom page
fault handler. This will single-step the faulted instruction with the
MMIO page marked as present. Access logs are directed to user space via
relay and debug_fs.

This page fault approach is necessary, because binary drivers have
readl/writel etc. calls inlined and therefore extremely difficult to
trap with with e.g. kprobes.

This patch depends on the custom page fault handlers patch.
Signed-off-by: NPekka Paalanen <pq@iki.fi>
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>

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>

Porting ftrace to the marker infrastructure.

Don't need to chain to the wakeup tracer from the sched tracer, because markers
support multiple probes connected.
Signed-off-by: NMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

To support the forthcoming "immediate values" marker optimization, we must have
a way to declare markers in few code paths that does not use instruction
modification based enable. This will be the case of printk(), some traps and
eventually lockdep instrumentation.

Changelog :
- Fix reversed boolean logic of "generic".
Signed-off-by: NMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Denys Vlasenko <vda.linux@googlemail.com> :

> Not in this patch, but I noticed:
>
> #define __trace_mark(name, call_private, format, args...)               \
>         do {                                                            \
>                 static const char __mstrtab_##name[]                    \
>                 __attribute__((section("__markers_strings")))           \
>                 = #name "\0" format;                                    \
>                 static struct marker __mark_##name                      \
>                 __attribute__((section("__markers"), aligned(8))) =     \
>                 { __mstrtab_##name, &__mstrtab_##name[sizeof(#name)],   \
>                 0, 0, marker_probe_cb,                                  \
>                 { __mark_empty_function, NULL}, NULL };                 \
>                 __mark_check_format(format, ## args);                   \
>                 if (unlikely(__mark_##name.state)) {                    \
>                         (*__mark_##name.call)                           \
>                                 (&__mark_##name, call_private,          \
>                                 format, ## args);                       \
>                 }                                                       \
>         } while (0)
>
> In this call:
>
>                         (*__mark_##name.call)                           \
>                                 (&__mark_##name, call_private,          \
>                                 format, ## args);                       \
>
> you make gcc allocate duplicate format string. You can use
> &__mstrtab_##name[sizeof(#name)] instead since it holds the same string,
> or drop ", format," above and "const char *fmt" from here:
>
>         void (*call)(const struct marker *mdata,        /* Probe wrapper */
>                 void *call_private, const char *fmt, ...);
>
> since mdata->format is the same and all callees which need it can take it there.

Very good point. I actually thought about dropping it, since it would
remove an unnecessary argument from the stack. And actually, since I now
have the marker_probe_cb sitting between the marker site and the
callbacks, there is no API change required. Thanks :)

Mathieu
Signed-off-by: NMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Denys Vlasenko <vda.linux@googlemail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Currently there is no protection from the root user to use up all of
memory for trace buffers. If the root user allocates too many entries,
the OOM killer might start kill off all tasks.

This patch adds an algorith to check the following condition:

 pages_requested > (freeable_memory + current_trace_buffer_pages) / 4

If the above is met then the allocation fails. The above prevents more
than 1/4th of freeable memory from being used by trace buffers.

To determine the freeable_memory, I made determine_dirtyable_memory in
mm/page-writeback.c global.

Special thanks goes to Peter Zijlstra for suggesting the above calculation.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
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>

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>

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>

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>

Since ftrace touches practically every function. If we detect any
anomaly, we want to fully disable ftrace. This patch adds code
to try shutdown ftrace as much as possible without doing any more
harm is something is detected not quite correct.

This only kills ftrace, this patch does have checks for other parts of
the tracer (irqsoff, wakeup, etc.).
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

The ftrace dynamic function update allocates a record to store the
instruction pointers that are being modified. If the modified
instruction pointer fails to update, then the record is marked as
failed and nothing more is done.

Worse, if the modification fails, but the record ip function is still
called, it will allocate a new record and try again. In just a matter
of time, will this cause a serious memory leak and crash the system.

This patch plugs this memory leak. When a record fails, it is
included back into the pool of records to be used. Now a record may
fail over and over again, but the number of allocated records will
not increase.
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 a startup self test on dynamic code modification
and filters. The test filters on a specific function, makes sure that
no other function is traced, exectutes the function, then makes sure that
the function is traced.

This patch also fixes a slight bug with the ftrace selftest, where
tracer_enabled was not being set.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
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>

disable the tracer while kexec pulls the rug from under the old
kernel.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

This patch adds two files to the debugfs system:

 /debugfs/tracing/available_filter_functions

and

 /debugfs/tracing/set_ftrace_filter

The available_filter_functions lists all functions that has been
recorded by the ftraced that has called the ftrace_record_ip function.
This is to allow users to see what functions have been converted
to nops and can be enabled for tracing.

To enable functions, simply echo the names (whitespace delimited)
into set_ftrace_filter. Simple wildcards are also allowed.

echo 'scheduler' > /debugfs/tracing/set_ftrace_filter

Will have only the scheduler be activated when tracing is enabled.

echo 'sched_*' > /debugfs/tracing/set_ftrace_filter

Will have only the functions starting with 'sched_' be activated.

echo '*lock' > /debugfs/tracing/set_ftrace_filter

Will have only functions ending with 'lock' be activated.

echo '*lock*' > /debugfs/tracing/set_ftrace_filter

Will have only functions with 'lock' in its name be activated.

Note: 'sched*lock' will not work. The only wildcards that are
allowed is an asterisk and the beginning and or end of the string
passed in.

Multiple names can be passed in with whitespace delimited:

echo 'scheduler *lock *acpi*' > /debugfs/tracing/set_ftrace_filter

is also the same as:

echo 'scheduler' > /debugfs/tracing/set_ftrace_filter
echo '*lock' >> /debugfs/tracing/set_ftrace_filter
echo '*acpi*' >> /debugfs/tracing/set_ftrace_filter

Appending does just that. It appends to the list.

To disable all filters simply echo an empty line in:

echo > /debugfs/tracing/set_ftrace_filter
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 replaces the indirect call to the mcount function
pointer with a direct call that will be patched by the
dynamic ftrace routines.

On boot up, the mcount function calls the ftace_stub function.
When the dynamic ftrace code is initialized, the ftrace_stub
is replaced with a call to the ftrace_record_ip, which records
the instruction pointers of the locations that call it.

Later, the ftraced daemon will call kstop_machine and patch all
the locations to nops.

When a ftrace is enabled, the original calls to mcount will now
be set top call ftrace_caller, which will do a direct call
to the registered ftrace function. This direct call is also patched
when the function that should be called is updated.

All patching is performed by a kstop_machine routine to prevent any
type of race conditions that is associated with modifying code
on the fly.
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 moves the memory management of the ftrace
records out of the arch code and into the generic code
making the arch code simpler.
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 back the sysctl ftrace_enabled. This time it is
defaulted to on, if DYNAMIC_FTRACE is configured. When ftrace_enabled
is disabled, the ftrace function is set to the stub return.

If DYNAMIC_FTRACE is also configured, on ftrace_enabled = 0,
the registered ftrace functions will all be set to jmps, but no more
new calls to ftrace recording (used to find the ftrace calling sites)
will be called.
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 a feature to dynamically replace the ftrace code
with the jmps to allow a kernel with ftrace configured to run
as fast as it can without it configured.

The way this works, is on bootup (if ftrace is enabled), a ftrace
function is registered to record the instruction pointer of all
places that call the function.

Later, if there's still any code to patch, a kthread is awoken
(rate limited to at most once a second) that performs a stop_machine,
and replaces all the code that was called with a jmp over the call
to ftrace. It only replaces what was found the previous time. Typically
the system reaches equilibrium quickly after bootup and there's no code
patching needed at all.

e.g.

  call ftrace  /* 5 bytes */

is replaced with

  jmp 3f  /* jmp is 2 bytes and we jump 3 forward */
3:

When we want to enable ftrace for function tracing, the IP recording
is removed, and stop_machine is called again to replace all the locations
of that were recorded back to the call of ftrace.  When it is disabled,
we replace the code back to the jmp.

Allocation is done by the kthread. If the ftrace recording function is
called, and we don't have any record slots available, then we simply
skip that call. Once a second a new page (if needed) is allocated for
recording new ftrace function calls.  A large batch is allocated at
boot up to get most of the calls there.

Because we do this via stop_machine, we don't have to worry about another
CPU executing a ftrace call as we modify it. But we do need to worry
about NMI's so all functions that might be called via nmi must be
annotated with notrace_nmi. When this code is configured in, the NMI code
will not call notrace.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Add preempt off timings. A lot of kernel core code is taken from the RT patch
latency trace that was written by Ingo Molnar.

This adds "preemptoff" and "preemptirqsoff" to /debugfs/tracing/available_tracers

Now instead of just tracing irqs off, preemption off can be selected
to be recorded.

When this is selected, it shares the same files as irqs off timings.
One can either trace preemption off, irqs off, or one or the other off.

By echoing "preemptoff" into /debugfs/tracing/current_tracer, recording
of preempt off only is performed. "irqsoff" will only record the time
irqs are disabled, but "preemptirqsoff" will take the total time irqs
or preemption are disabled. Runtime switching of these options is now
supported by simpling echoing in the appropriate trace name into
/debugfs/tracing/current_tracer.
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 latency tracing for critical timings
(how long interrupts are disabled for).

 "irqsoff" is added to /debugfs/tracing/available_tracers

Note:
  tracing_max_latency
    also holds the max latency for irqsoff (in usecs).
   (default to large number so one must start latency tracing)

  tracing_thresh
    threshold (in usecs) to always print out if irqs off
    is detected to be longer than stated here.
    If irq_thresh is non-zero, then max_irq_latency
    is ignored.

Here's an example of a trace with ftrace_enabled = 0

=======
preemption latency trace v1.1.5 on 2.6.24-rc7
Signed-off-by: NIngo Molnar <mingo@elte.hu>
--------------------------------------------------------------------
 latency: 100 us, #3/3, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
    -----------------
 => started at: _spin_lock_irqsave+0x2a/0xb7
 => ended at:   _spin_unlock_irqrestore+0x32/0x5f

                 _------=> CPU#
                / _-----=> irqs-off
               | / _----=> need-resched
               || / _---=> hardirq/softirq
               ||| / _--=> preempt-depth
               |||| /
               |||||     delay
   cmd     pid ||||| time  |   caller
      \   /    |||||   \   |   /
 swapper-0     1d.s3    0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
 swapper-0     1d.s3  100us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1d.s3  100us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)

vim:ft=help
=======

And this is a trace with ftrace_enabled == 1

=======
preemption latency trace v1.1.5 on 2.6.24-rc7
--------------------------------------------------------------------
 latency: 102 us, #12/12, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
    -----------------
 => started at: _spin_lock_irqsave+0x2a/0xb7
 => ended at:   _spin_unlock_irqrestore+0x32/0x5f

                 _------=> CPU#
                / _-----=> irqs-off
               | / _----=> need-resched
               || / _---=> hardirq/softirq
               ||| / _--=> preempt-depth
               |||| /
               |||||     delay
   cmd     pid ||||| time  |   caller
      \   /    |||||   \   |   /
 swapper-0     1dNs3    0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
 swapper-0     1dNs3   46us : e1000_read_phy_reg+0x16/0x225 [e1000] (e1000_update_stats+0x5e2/0x64c [e1000])
 swapper-0     1dNs3   46us : e1000_swfw_sync_acquire+0x10/0x99 [e1000] (e1000_read_phy_reg+0x49/0x225 [e1000])
 swapper-0     1dNs3   46us : e1000_get_hw_eeprom_semaphore+0x12/0xa6 [e1000] (e1000_swfw_sync_acquire+0x36/0x99 [e1000])
 swapper-0     1dNs3   47us : __const_udelay+0x9/0x47 (e1000_read_phy_reg+0x116/0x225 [e1000])
 swapper-0     1dNs3   47us+: __delay+0x9/0x50 (__const_udelay+0x45/0x47)
 swapper-0     1dNs3   97us : preempt_schedule+0xc/0x84 (__delay+0x4e/0x50)
 swapper-0     1dNs3   98us : e1000_swfw_sync_release+0xc/0x55 [e1000] (e1000_read_phy_reg+0x211/0x225 [e1000])
 swapper-0     1dNs3   99us+: e1000_put_hw_eeprom_semaphore+0x9/0x35 [e1000] (e1000_swfw_sync_release+0x50/0x55 [e1000])
 swapper-0     1dNs3  101us : _spin_unlock_irqrestore+0xe/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1dNs3  102us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1dNs3  102us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)

vim:ft=help
=======
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 tracer that tracks the wakeup latency of the
highest priority waking task.

  "wakeup" is added to /debugfs/tracing/available_tracers

Also added to /debugfs/tracing

  tracing_max_latency
     holds the current max latency for the wakeup

  wakeup_thresh
     if set to other than zero, a log will be recorded
     for every wakeup that takes longer than the number
     entered in here (usecs for all counters)
     (deletes previous trace)

Examples:

  (with ftrace_enabled = 0)

============
preemption latency trace v1.1.5 on 2.6.24-rc8
Signed-off-by: NIngo Molnar <mingo@elte.hu>
--------------------------------------------------------------------
 latency: 26 us, #2/2, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: migration/0-3 (uid:0 nice:-5 policy:1 rt_prio:99)
    -----------------

                 _------=> CPU#
                / _-----=> irqs-off
               | / _----=> need-resched
               || / _---=> hardirq/softirq
               ||| / _--=> preempt-depth
               |||| /
               |||||     delay
   cmd     pid ||||| time  |   caller
      \   /    |||||   \   |   /
   quilt-8551  0d..3    0us+: wake_up_process+0x15/0x17 <ffffffff80233e80> (sched_exec+0xc9/0x100 <ffffffff80235343>)
   quilt-8551  0d..4   26us : sched_switch_callback+0x73/0x81 <ffffffff80338d2f> (schedule+0x483/0x6d5 <ffffffff8048b3ee>)

vim:ft=help
============

  (with ftrace_enabled = 1)

============
preemption latency trace v1.1.5 on 2.6.24-rc8
--------------------------------------------------------------------
 latency: 36 us, #45/45, CPU#0 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: migration/1-5 (uid:0 nice:-5 policy:1 rt_prio:99)
    -----------------

                 _------=> CPU#
                / _-----=> irqs-off
               | / _----=> need-resched
               || / _---=> hardirq/softirq
               ||| / _--=> preempt-depth
               |||| /
               |||||     delay
   cmd     pid ||||| time  |   caller
      \   /    |||||   \   |   /
    bash-10653 1d..3    0us : wake_up_process+0x15/0x17 <ffffffff80233e80> (sched_exec+0xc9/0x100 <ffffffff80235343>)
    bash-10653 1d..3    1us : try_to_wake_up+0x271/0x2e7 <ffffffff80233dcf> (sub_preempt_count+0xc/0x7a <ffffffff8023309e>)
    bash-10653 1d..2    2us : try_to_wake_up+0x296/0x2e7 <ffffffff80233df4> (update_rq_clock+0x9/0x20 <ffffffff802303f3>)
    bash-10653 1d..2    2us : update_rq_clock+0x1e/0x20 <ffffffff80230408> (__update_rq_clock+0xc/0x90 <ffffffff80230366>)
    bash-10653 1d..2    3us : __update_rq_clock+0x1b/0x90 <ffffffff80230375> (sched_clock+0x9/0x29 <ffffffff80214529>)
    bash-10653 1d..2    4us : try_to_wake_up+0x2a6/0x2e7 <ffffffff80233e04> (activate_task+0xc/0x3f <ffffffff8022ffca>)
    bash-10653 1d..2    4us : activate_task+0x2d/0x3f <ffffffff8022ffeb> (enqueue_task+0xe/0x66 <ffffffff8022ff66>)
    bash-10653 1d..2    5us : enqueue_task+0x5b/0x66 <ffffffff8022ffb3> (enqueue_task_rt+0x9/0x3c <ffffffff80233351>)
    bash-10653 1d..2    6us : try_to_wake_up+0x2ba/0x2e7 <ffffffff80233e18> (check_preempt_wakeup+0x12/0x99 <ffffffff80234f84>)
[...]
    bash-10653 1d..5   33us : tracing_record_cmdline+0xcf/0xd4 <ffffffff80338aad> (_spin_unlock+0x9/0x33 <ffffffff8048d3ec>)
    bash-10653 1d..5   34us : _spin_unlock+0x19/0x33 <ffffffff8048d3fc> (sub_preempt_count+0xc/0x7a <ffffffff8023309e>)
    bash-10653 1d..4   35us : wakeup_sched_switch+0x65/0x2ff <ffffffff80339f66> (_spin_lock_irqsave+0xc/0xa9 <ffffffff8048d08b>)
    bash-10653 1d..4   35us : _spin_lock_irqsave+0x19/0xa9 <ffffffff8048d098> (add_preempt_count+0xe/0x77 <ffffffff8023311a>)
    bash-10653 1d..4   36us : sched_switch_callback+0x73/0x81 <ffffffff80338d2f> (schedule+0x483/0x6d5 <ffffffff8048b3ee>)

vim:ft=help
============

The [...] was added here to not waste your email box space.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

If CONFIG_FTRACE is selected and /proc/sys/kernel/ftrace_enabled is
set to a non-zero value the ftrace routine will be called everytime
we enter a kernel function that is not marked with the "notrace"
attribute.

The ftrace routine will then call a registered function if a function
happens to be registered.

[ This code has been highly hacked by Steven Rostedt and Ingo Molnar,
  so don't blame Arnaldo for all of this ;-) ]

Update:
  It is now possible to register more than one ftrace function.
  If only one ftrace function is registered, that will be the
  function that ftrace calls directly. If more than one function
  is registered, then ftrace will call a function that will loop
  through the functions to call.
Signed-off-by: NArnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

notrace signals that a function should not be traced. Most of the
time this is used by tracers to annotate code that cannot be
traced - it's in a volatile state (such as in user vdso context
or NMI context) or it's in the tracer internals.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

The tracer may need to call preempt_enable and disable functions
for time keeping and such. The trace gets ugly when we see these
functions show up for all traces. To make the output cleaner
this patch adds preempt_enable_notrace and preempt_disable_notrace
to be used by tracer (and debugging) functions.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

The tracer wants to be able to convert the state number
into a user visible character. This patch pulls that conversion
string out the scheduler into the header. This way if it were to
ever change, other parts of the kernel will know.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

add 3 lightweight callbacks to the tracer backend.

zero impact if tracing is turned off.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

If previous window was above representable values of u16,
strange things will happen if undo with the truncated value
is called for. Alternatively, this could be fixed by some
max trickery but that would limit undoing high-speed undos.

Adds 16-bit hole but there isn't anything to fill it with.
Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Greg Steuck <greg@nest.cx> points out that some of the netfilter
headers can't be used in userspace without including linux/types.h
first. The headers include their own linux/types.h include statements,
these are stripped by make headers-install because they are inside
#ifdef __KERNEL__ however. Move them out to fix this.

Reported and Tested by Greg Steuck.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>