* change function names to clear_* from set_*: in reality we only clear
  and restore page presence, and never unconditionally set present.
  Using clear_*({true, false}, ...) is therefore more honest than
  set_*({false, true}, ...)

* upgrade presence storage to pteval_t: doing user-space tracing will
  require saving and manipulation of the _PAGE_PROTNONE bit, in addition
  to the existing _PAGE_PRESENT changes, and having multiple bools stored
  and passed around does not seem optimal

[ Impact: refactor, clean up mmiotrace code ]
Signed-off-by: Stuart Bennett <stuart@freedesktop.org>
Acked-by: Pekka Paalanen <pq@iki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1240946271-7083-4-git-send-email-stuart@freedesktop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kmmio_probe being *p and kmmio_fault_page being sometimes *f and
sometimes *p is not helpful.

[ Impact: cleanup ]
Signed-off-by: Stuart Bennett <stuart@freedesktop.org>
Acked-by: Pekka Paalanen <pq@iki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1240946271-7083-3-git-send-email-stuart@freedesktop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

The warning output in trace_recursive_lock uses %d for a long when
it should be %ld.

[ Impact: fix compile warning ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Splice works with pages, it is much more effecient to use an entire
page than to copy bits over several pages.

Using logdev to trace the internals of the splice mechanism, I was
able to see that splice can be very aggressive. When tracing is
occurring, and the reader caught up to the writer, and the writer
is on the reader page, the reader will copy what is there into the
splice page. Splice may iterate over several pages and if the
writer is still writing to the page, the reader will keep copying
bits to new pages to pass to userspace.

This patch changes it to only pass data to userspace if the page
is full (the writer has left the page). This has a small side effect
that splice can not read a partial page, and must wait for the
page to fill. This should not be an issue. If tracing has stopped,
then a use of "read" will still read all of the page.

[ Impact: better performance for ring buffer splice code ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

The splice code allocates a page even when the ring buffer is empty.
It detects the ring buffer being empty when it it fails to copy
anything from the ring buffer into the page.

This patch adds a check to see if there is anything in the ring buffer
before allocating a page.

Thanks to logdev for letting me trace the tracer to find this.

[ Impact: speed up due to removing unnecessary allocation ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

The pages allocated for the splice binary buffer did not initialize
the ref count correctly. This caused pages not to be freed and causes
a drastic memory leak.

Thanks to logdev I was able to trace the tracer to find where the leak
was.

[ Impact: stop memory leak when using splice ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

ftrace_dump is used for printing out the contents of the ftrace ring buffer
to the console on failure. Currently it uses a spinlock to synchronize
the output from multiple failures on different CPUs. This spin lock
currently is a normal spinlock and can cause issues with lockdep and
lock tracing.

This patch converts it to raw since it is for error handling only.
The lock is local to the ftrace_dump and is not used by any other
infrastructure.

[ Impact: prevent ftrace_dump from locking up by internal tracing ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

For proper module reference counting, the file_operations that modules use
must have the "owner" field set to the module. Unfortunately, the trace events
use share file_operations. The same file_operations are used by all both
kernel core and all modules.

This patch makes the modules allocate their own file_operations and
copies the functions from the core kernel. This allows those file
operations to be owned by the module.

Care is taken to free this code on module unload.

Thanks to Greg KH for reminding me that file_operations must be owned
by the module to have reference counting take place.

[ Impact: fix modular tracepoints / potential crash ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>

With modules being able to add trace events, and the max trace event
counter is 16 bits (65536) we can overflow the counter easily
with a simple while loop adding and removing modules that contain
trace events.

This patch links together the registered trace events and on overflow
searches for available trace event ids. It will still fail if
over 65536 events are registered, but considering that a typical
kernel only has 22000 functions, 65000 events should be sufficient.
Reported-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

The TRACE_FORMAT macro has been deprecated by the TRACE_EVENT macro.
There are no more users. All new users must use the TRACE_EVENT macro.

[ Impact: remove old functionality ]

Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

The TRACE_FORMAT will soon be deprecated. This patch converts it to
the TRACE_EVENT macro.

Note, this change should also speed up the tracing.

[ Impact: remove a user of deprecated TRACE_FORMAT ]

Cc: Jason Baron <jbaron@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

The TRACE_FORMAT will soon be deprecated. This patch converts it to
the TRACE_EVENT macro.

Note, this change should also speed up the tracing.

[ Impact: remove a user of deprecated TRACE_FORMAT ]

Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes
an 'u32' to save the actually length for events which data size > 28.

This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA.

[ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ]
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <49F13189.3090000@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

In case a module uses the TRACE_EVENT macro for creating automated
events in ftrace, it may choose to use a different file name
than the defined system name, or choose to use a different path than
the default "include/trace/events" include path.

If this is done, then before including trace/define_trace.h the
header would define either "TRACE_INCLUDE_FILE" for the file
name or "TRACE_INCLUDE_PATH" for the include path.

If it does not define these, then the define_trace.h defines them
instead. If define trace defines them, then define_trace.h should
also undefine them before exiting. To do this a macro is used
to note this:

 #ifndef TRACE_INCLUDE_FILE
 # define TRACE_INCLUDE_FILE TRACE_SYSTEM
 # define UNDEF_TRACE_INCLUDE_FILE
 #endif

[...]

 #ifdef UNDEF_TRACE_INCLUDE_FILE
 # undef TRACE_INCLUDE_FILE
 # undef UNDEF_TRACE_INCLUDE_FILE
 #endif

The UNDEF_TRACE_INCLUDE_FILE acts as a CPP variable to know to undef
the TRACE_INCLUDE_FILE before leaving define_trace.h.

Unfortunately, due to cut and paste errors, the macros between
FILE and PATH got mixed up.

[ Impact: undef TRACE_INCLUDE_FILE and/or TRACE_INCLUDE_PATH when needed ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

currently these are paravirtulaized, doesn't appear any callers rely on
this (no pv_ops backends are using native_tlb and overriding cr3/4
access).

[ Impact: fix lockdep warning with paravirt and function tracer ]
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
LKML-Reference: <20090423172138.GR3036@sequoia.sous-sol.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

The events exported by TRACE_EVENT are automated and are guaranteed
to be correct when used.

The internal ftrace structures on the other hand are more manually
exported. These require the ftrace maintainer to make sure they
are up to date.

This patch adds a size check to help flag when a type changes in
an internal ftrace data structure, and the update needs to be reflected
in the export.

If a export is incorrect, then the only harm is that the user space
tools will not know how to correctly read the internal structures of
ftrace.

[ Impact: help prevent inconsistent ftrace format print outs ]
Signed-off-by: Steven Rostedt <srostedt@redhat.com>

With the new event tracing registration, we must increase the number
of events that can be registered. Currently the type field is only
one byte, which leaves us only 256 possible events.

Since we do not save the CPU number in the tracer anymore (it is determined
by the per cpu ring buffer that is used) we have an extra byte to use.

This patch increases the size of type from 1 byte (256 events) to
2 bytes (65,536 events).

It also adds a WARN_ON_ONCE if we exceed that limit.

[ Impact: allow more than 255 events ]
Signed-off-by: Steven Rostedt <srostedt@redhat.com>

The code had the following outside the lock:

        if (next != wakeup_task)
                return;

        pc = preempt_count();

        /* The task we are waiting for is waking up */
        data = wakeup_trace->data[wakeup_cpu];

On initialization, wakeup_task is NULL and wakeup_cpu -1. This code
is not under a lock. If wakeup_task is set on another CPU as that
task is waking up, we can see the wakeup_task before wakeup_cpu is
set. If we read wakeup_cpu while it is still -1 then we will have
a bad data pointer.

This patch moves the reading of wakeup_cpu within the protection of
the spinlock used to protect the writing of wakeup_cpu and wakeup_task.

[ Impact: remove possible race causing invalid pointer dereference ]
Reported-by: Maneesh Soni <maneesh@in.ibm.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>

The __get_str() macro is used in a code part then its content should be
protected with parenthesis.

[ Impact: make macro definition more robust ]
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

Now that we can support the dynamic sized string, make the lock tracing
able to use it, making it safe against modules removal and consuming
the right amount of memory needed for each lock name

Changes in v2:
adapt to the __ending_string() updates and the opening_string() removal.

[ Impact: protect lock tracer against module removal ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>

This patch provides the support for dynamic size strings on
event tracing.

The key concept is to use a structure with an ending char array field of
undefined size and use such ability to allocate the minimal size on the
ring buffer to make one or more string entries fit inside, as opposite
to a fixed length strings with upper bound.

The strings themselves are represented using fields which have an offset
value from the beginning of the entry.

This patch provides three new macros:

__string(item, src)

This one declares a string to the structure inside TP_STRUCT__entry.
You need to provide the name of the string field and the source that will
be copied inside.
This will also add the dynamic size of the string needed for the ring
buffer entry allocation.
A stack allocated structure is used to temporarily store the offset
of each strings, avoiding double calls to strlen() on each event
insertion.

__get_str(field)

This one will give you a pointer to the string you have created. This
is an abstract helper to resolve the absolute address given the field
name which is a relative address from the beginning of the trace_structure.

__assign_str(dst, src)

Use this macro to automatically perform the string copy from src to
dst. src must be a variable to assign and dst is the name of a __string
field.

Example on how to use it:

TRACE_EVENT(my_event,
	TP_PROTO(char *src1, char *src2),

	TP_ARGS(src1, src2),
	TP_STRUCT__entry(
		__string(str1, src1)
		__string(str2, src2)
	),
	TP_fast_assign(
		__assign_str(str1, src1);
		__assign_str(str2, src2);
	),
	TP_printk("%s %s", __get_str(src1), __get_str(src2))
)

Of course you can mix-up any __field or __array inside this
TRACE_EVENT. The position of the __string or __assign_str
doesn't matter.

Changes in v2:

Address the suggestion of Steven Rostedt: drop the opening_string() macro
and redefine __ending_string() to get the size of the string to be copied
instead of overwritting the whole ring buffer allocation.

Changes in v3:

Address other suggestions of Steven Rostedt and Peter Zijlstra with
some changes: drop the __ending_string and the need to have only one
string field.
Use offsets instead of absolute addresses.

[ Impact: allow more compact memory usage for string tracing ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>

struct trace_entry->type is unsigned char, while trace event's id is
int type, thus for a event with id >= 256, it's entry->type is cast
to (id % 256), and then we can't see the trace output of this event.

 # insmod trace-events-sample.ko
 # echo foo_bar > /mnt/tracing/set_event
 # cat /debug/tracing/events/trace-events-sample/foo_bar/id
 256
 # cat /mnt/tracing/trace_pipe
           <...>-3548  [001]   215.091142: Unknown type 0
           <...>-3548  [001]   216.089207: Unknown type 0
           <...>-3548  [001]   217.087271: Unknown type 0
           <...>-3548  [001]   218.085332: Unknown type 0

[ Impact: fix output for trace events with id >= 256 ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <49EEDB0E.5070207@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

On boot up, to save memory, ftrace allocates the minimum buffer
which is two pages. Ftrace also goes through a series of tests
(when configured) on boot up. These tests can fill up a page within
a single interrupt.

The ring buffer also has a WARN_ON when it detects that the buffer was
completely filled within a single commit (other commits are allowed to
be nested).

Combine the small buffer on start up, with the tests that can fill more
than a single page within an interrupt, this can trigger the WARN_ON.

This patch makes the WARN_ON only happen when the ring buffer consists
of more than two pages.

[ Impact: prevent false WARN_ON in ftrace startup tests ]
Reported-by: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <20090421094616.GA14561@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Suppose we would like to trace all tasks named '123', but this
will fail:

 # echo 'parent_comm == 123' > events/sched/sched_process_fork/filter
 bash: echo: write error: Invalid argument

Don't guess the type of the filter pred in filter_parse(), but instead
we check it in __filter_add_pred().

[ Impact: extend allowed filter field string values ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <49ED8DEB.6000700@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

If writing subsys->filter returns EINVAL or ENOSPC, the original
filters in subsys/ and subsys/events/ will be removed. This is
definitely wrong.

[ Impact: fix filter setting semantics on error condition ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <49ED8DD2.2070700@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

The startup tests for the event tracer also runs with the function
tracer enabled. The "wakeup" version of the trace commit was used
which can grab spinlocks. If a task was preempted by an NMI
that called a function being traced, it could deadlock due to the
function tracer trying to grab the same lock.

Thanks to Frederic Weisbecker for pointing out where the bug was.
Reported-by: Ingo Molnar <mingo@elte.hu>
Reported-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Althought using the irq level (hardirq_count, softirq_count and in_nmi)
was nice to detect bad recursion right away, but since the counters are
not atomically updated with respect to the interrupts, the function tracer
might trigger the test from an interrupt handler before the hardirq_count
is updated. This will trigger a false warning.

This patch converts the recursive detection to a simple counter.
If the depth is greater than 16 then the recursive detection will trigger.
16 is more than enough for any nested interrupts.

[ Impact: fix false positive trace recursion detection ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

The ring_buffer_event_discard is not tied to ring_buffer_lock_reserve.
It can be called inside or outside the reserve/commit. Even if it
is called inside the reserve/commit the commit part must also be called.

Only ring_buffer_discard_commit can be used as a replacement for
ring_buffer_unlock_commit.

This patch removes the trace_recursive_unlock from ring_buffer_event_discard
since it would be the wrong place to do so.

[Impact: prevent breakage in trace recursive testing ]

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

The recursive tests to detect same level recursion in the ring buffers
did not account for the hard/softirq_counts to be shifted. Thus the
numbers could be larger than then mask to be tested.

This patch includes the shift for the calculation of the irq depth.

[ Impact: stop false positives in trace recursion detection ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Due to a cut and paste error, the trace_seq_putc had a semicolon
after the prototype but before the stub function when tracing is
disabled.

[Impact: fix compile error ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

The late_initcall calls a helper function instead of the proper
init event selftest function.

This update may have been lost due to conflicting merges.

[ Impact: fix compiler warning and call extended event trace self tests ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Currently we have two configs: EVENT_TRACING and EVENT_TRACER.
All tracers enable EVENT_TRACING. The EVENT_TRACER is only a
convenience to enable the EVENT_TRACING when no other tracers
are enabled.

The names EVENT_TRACER and EVENT_TRACING are too similar and confusing.
This patch renames EVENT_TRACER to ENABLE_EVENT_TRACING to be more
appropriate to what it actually does, as well as add a comment in
the help menu to explain the option's purpose.

[ Impact: rename config option to reduce confusion ]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

During testing we often use randconfig to test various kernels.
The current configuration set up does not give an easy way to disable
all tracing with a single config. The case where randconfig would
test all tracing disabled is very unlikely.

This patch adds a config option to enable or disable all tracing.
It is hooked into the tracing menu just like other submenus are done.

[ Impact: allow randconfig to easily produce all traces disabled ]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

This patch makes the branch profiling into a choice selection:

  None               - no branch profiling
  likely/unlikely    - only profile likely/unlikely branches
  all                - profile all branches

The all profiler will also enable the likely/unlikely branches.

This does not change the way the profiler works or the dependencies
between the profilers.

What this patch does, is keep the branch profiling from being selected
by an allyesconfig make. The branch profiler is very intrusive and
it is known to break various architecture builds when selected as an
allyesconfig.

[ Impact: prevent branch profiler from being selected in allyesconfig ]
Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

The pair of helpers trace_recursive_lock() and trace_recursive_unlock()
have been introduced recently to provide generic tracing recursion
protection.

They are used in a symetric way:

 - trace_recursive_lock() on buffer reserve
 - trace_recursive_unlock() on buffer commit

However sometimes, we don't commit but discard on entry
to the buffer, ie: in case of filter checking.

Then we must also unlock the recursion protection on discard time,
otherwise the tracing gets definitely deactivated and a warning
is raised spuriously, such as:

111.119821] ------------[ cut here ]------------
[  111.119829] WARNING: at kernel/trace/ring_buffer.c:1498 ring_buffer_lock_reserve+0x1b7/0x1d0()
[  111.119835] Hardware name: AMILO Li 2727
[  111.119839] Modules linked in:
[  111.119846] Pid: 5731, comm: Xorg Tainted: G        W  2.6.30-rc1 #69
[  111.119851] Call Trace:
[  111.119863]  [<ffffffff8025ce68>] warn_slowpath+0xd8/0x130
[  111.119873]  [<ffffffff8028a30f>] ? __lock_acquire+0x19f/0x1ae0
[  111.119882]  [<ffffffff8028a30f>] ? __lock_acquire+0x19f/0x1ae0
[  111.119891]  [<ffffffff802199b0>] ? native_sched_clock+0x20/0x70
[  111.119899]  [<ffffffff80286dee>] ? put_lock_stats+0xe/0x30
[  111.119906]  [<ffffffff80286eb8>] ? lock_release_holdtime+0xa8/0x150
[  111.119913]  [<ffffffff802c8ae7>] ring_buffer_lock_reserve+0x1b7/0x1d0
[  111.119921]  [<ffffffff802cd110>] trace_buffer_lock_reserve+0x30/0x70
[  111.119930]  [<ffffffff802ce000>] trace_current_buffer_lock_reserve+0x20/0x30
[  111.119939]  [<ffffffff802474e8>] ftrace_raw_event_sched_switch+0x58/0x100
[  111.119948]  [<ffffffff808103b7>] __schedule+0x3a7/0x4cd
[  111.119957]  [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b
[  111.119964]  [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b
[  111.119971]  [<ffffffff80810c08>] schedule+0x18/0x40
[  111.119977]  [<ffffffff80810e09>] preempt_schedule+0x39/0x60
[  111.119985]  [<ffffffff80813bd3>] _read_unlock+0x53/0x60
[  111.119993]  [<ffffffff807259d2>] sock_def_readable+0x72/0x80
[  111.120002]  [<ffffffff807ad5ed>] unix_stream_sendmsg+0x24d/0x3d0
[  111.120011]  [<ffffffff807219a3>] sock_aio_write+0x143/0x160
[  111.120019]  [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b
[  111.120026]  [<ffffffff80721860>] ? sock_aio_write+0x0/0x160
[  111.120033]  [<ffffffff80721860>] ? sock_aio_write+0x0/0x160
[  111.120042]  [<ffffffff8031c283>] do_sync_readv_writev+0xf3/0x140
[  111.120049]  [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b
[  111.120057]  [<ffffffff80276ff0>] ? autoremove_wake_function+0x0/0x40
[  111.120067]  [<ffffffff8045d489>] ? cap_file_permission+0x9/0x10
[  111.120074]  [<ffffffff8045c1e6>] ? security_file_permission+0x16/0x20
[  111.120082]  [<ffffffff8031cab4>] do_readv_writev+0xd4/0x1f0
[  111.120089]  [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b
[  111.120097]  [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b
[  111.120105]  [<ffffffff8031cc18>] vfs_writev+0x48/0x70
[  111.120111]  [<ffffffff8031cd65>] sys_writev+0x55/0xc0
[  111.120119]  [<ffffffff80211e32>] system_call_fastpath+0x16/0x1b
[  111.120125] ---[ end trace 15605f4e98d5ccb5 ]---

[ Impact: fix spurious warning triggering tracing shutdown ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

In case of tracing recursion detection, we only get the stacktrace.
But the current context may be very useful to debug the issue.

This patch adds the softirq/hardirq/nmi context with the warning
using lockdep context display to have a familiar output.

v2: Use printk_once()
v3: drop {hardirq,softirq}_context which depend on lockdep,
    only keep what is part of current->trace_recursion,
    sufficient to debug the warning source.

[ Impact: print context necessary to debug recursion ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

Due to a cut and paste error, I added the gcc attribute for printf
format to the static inline stub of trace_seq_printf.

This will cause a compile failure.

[ Impact: fix compiler error when CONFIG_TRACING is off ]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: =?ISO-8859-15?Q?Fr=E9d=E9ric_Weisbecker?= <fweisbec@gmail.com>
LKML-Reference: <alpine.DEB.2.00.0904171717080.1016@gandalf.stny.rr.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

trace_printk can be called from any context, including NMIs.
If this happens, then we must test for for recursion before
grabbing any spinlocks.

This patch prevents trace_printk from being called recursively.

[ Impact: prevent hard lockup in lockdep event tracer ]

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

The tracing infrastructure allows for recursion. That is, an interrupt
may interrupt the act of tracing an event, and that interrupt may very well
perform its own trace. This is a recursive trace, and is fine to do.

The problem arises when there is a bug, and the utility doing the trace
calls something that recurses back into the tracer. This recursion is not
caused by an external event like an interrupt, but by code that is not
expected to recurse. The result could be a lockup.

This patch adds a bitmask to the task structure that keeps track
of the trace recursion. To find the interrupt depth, the following
algorithm is used:

  level = hardirq_count() + softirq_count() + in_nmi;

Here, level will be the depth of interrutps and softirqs, and even handles
the nmi. Then the corresponding bit is set in the recursion bitmask.
If the bit was already set, we know we had a recursion at the same level
and we warn about it and fail the writing to the buffer.

After the data has been committed to the buffer, we clear the bit.
No atomics are needed. The only races are with interrupts and they reset
the bitmask before returning anywy.

[ Impact: detect same irq level trace recursion ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Not all the necessary symbols were exported to allow for tracing
by modules. This patch adds them in.

[ Impact: allow modules to commit data to the ring buffer ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>