Li Zefan found that there's a race using the event ids of events and
modules. When a module is loaded, an event id is incremented. We only
have 16 bits for event ids (65536) and there is a possible (but highly
unlikely) race that we could load and unload a module that registers
events so many times that the event id counter overflows.

When it overflows, it then restarts and goes looking for available
ids. An id is available if it was added by a module and released.

The race is if you have one module add an id, and then is removed.
Another module loaded can use that same event id. But if the old module
still had events in the ring buffer, the new module's call back would
get bogus data.  At best (and most likely) the output would just be
garbage. But if the module for some reason used pointers (not recommended)
then this could potentially crash.

The safest thing to do is just reset the ring buffer if a module that
registered events is removed.

[ Impact: prevent unpredictable results of event id overflows ]
Reported-by: NLi Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <49FEAFD0.30106@cn.fujitsu.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

When creating trace events for ftrace, the header file with the TRACE_EVENT
macros must also have a macro called TRACE_SYSTEM. This macro describes
the name of the system the TRACE_EVENTS are defined for. It also doubles
as a way for the define_trace.h file to include the file that included
it.

For example:

in irq.h

 #define TRACE_SYSTEM irq

[...]

 #include <trace/define_trace.h>

The define_trace will use TRACE_SYSTEM to include irq.h. But if the name
of the trace system does not match the name of the trace header file,
one can override it with:

Which will change define_trace.h to inclued foo_trace.h instead of foo.h

The sample comments this, but people that use the sample code will more
likely use the code and not read the comments. This patch changes the
sample code to use the TRACE_INCLUDE_FILE to better show developers how to
use it.

[ Impact: make sample less confusing to developers ]
Reported-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The ring buffer benchmark/test runs a producer for 10 seconds.
This is done with preemption and interrupts enabled. But if the kernel
is not compiled with CONFIG_PREEMPT, it basically stops everything
but interrupts for 10 seconds.

Although this is just a test and is not for production, this attribute
can be quite annoying. It can also spawn badness elsewhere.

This patch solves the issues by calling "cond_resched" when the system
is not compiled with CONFIG_PREEMPT. It also keeps track of the time
spent to call cond_resched such that it does not go against the
time calculations. That is, if the task schedules away, the time scheduled
out is removed from the test data. Note, this only works for non PREEMPT
because we do not know when the task is scheduled out if we have PREEMPT
enabled.

[ Impact: prevent test from stopping the world for 10 seconds ]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Ingo Molnar thought the code would be cleaner if we used a function call
instead of a goto for moving the tail page. After implementing this,
it seems that gcc still inlines the result and the output is pretty much
the same. Since this is considered a cleaner approach, might as well
implement it.

[ Impact: code clean up ]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The result of the allocation of the ring buffer read page in the
ring buffer bench mark does not check the return to see if a page
was actually allocated. This patch fixes that.

[ Impact: avoid NULL dereference ]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The code in __rb_reserve_next checks on page overflow if it is the
original commiter and then resets the page back to the original
setting.  Although this is fine, and the code is correct, it is
a bit fragil. Some experimental work I did breaks it easily.

The better and more robust solution is to have all commiters that
overflow the page, simply subtract what they added.

[ Impact: more robust ring buffer account management ]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Use -I$(src) to add the current directory the include path.

[ Impact: cleanup ]
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

This compiler warning:

  CC      kernel/trace/trace_output.o
 kernel/trace/trace_output.c: In function ‘register_ftrace_event’:
 kernel/trace/trace_output.c:544: warning: ‘list’ may be used uninitialized in this function

Is wrong as 'list' is always initialized - but GCC (4.3.2) does not
recognize this relationship properly.

Work around the warning by initializing the variable to NULL.

[ Impact: fix false positive compiler warning ]
Signed-off-by: NJaswinder Singh Rajput <jaswinderrajput@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Remove redundant from-sector parameter: it's /always/ the bio's sector
passed in.

[ Impact: cleanup ]
Signed-off-by: NAlan D. Brunelle <alan.brunelle@hp.com>
Reviewed-by: NLi Zefan <lizf@cn.fujitsu.com>
Reviewed-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <49FF517C.7000503@hp.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

This attempts to clarify names utilized during block I/O remap
operations (partition, volume manager). It correctly matches up the
/from/ information for both device & sector. This takes in the concept
from Kosaki Motohiro and extends it to include better naming for the
"device_from" field.

[ Impact: cleanup ]
Signed-off-by: NAlan D. Brunelle <alan.brunelle@hp.com>
Reviewed-by: NLi Zefan <lizf@cn.fujitsu.com>
Reviewed-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <49FF4FAE.3000301@hp.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The orig_cpu parameter in trace_sched_migrate_task() is not necessary,
it can be got by using task_cpu(p) in the probe.

[ Impact: micro-optimization ]
Signed-off-by: NMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
[ modified from Mathieu's patch. The original patch is at:
  http://marc.info/?l=linux-kernel&m=123791201716239&w=2 ]
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: fweisbec@gmail.com
Cc: rostedt@goodmis.org
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: zhaolei@cn.fujitsu.com
Cc: laijs@cn.fujitsu.com
LKML-Reference: <49FFFDB7.1050402@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

A module will add/remove its trace events when it gets loaded/unloaded, so
the ftrace_events list is not "const", and concurrent access needs to be
protected.

This patch thus fixes races between loading/unloding modules and read
'available_events' or read/write 'set_event', etc.

Below shows how to reproduce the race:

 # for ((; ;)) { cat /mnt/tracing/available_events; } > /dev/null &
 # for ((; ;)) { insmod trace-events-sample.ko; rmmod sample; } &

After a while:

BUG: unable to handle kernel paging request at 0010011c
IP: [<c1080f27>] t_next+0x1b/0x2d
...
Call Trace:
 [<c10c90e6>] ? seq_read+0x217/0x30d
 [<c10c8ecf>] ? seq_read+0x0/0x30d
 [<c10b4c19>] ? vfs_read+0x8f/0x136
 [<c10b4fc3>] ? sys_read+0x40/0x65
 [<c1002a68>] ? sysenter_do_call+0x12/0x36

[ Impact: fix races when concurrent accessing ftrace_events list ]
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4A00F709.3080800@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

When unloading a module, memory allocated by init_preds() and
trace_define_field() is not freed.

[ Impact: fix memory leak ]
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <4A00F6E0.3040503@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Normally a config should be default to n. This patch also makes the
sample module-only, like SAMPLE_MARKERS and SAMPLE_TRACEPOINTS.

[ Impact: don't build trace event sample by default ]
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A00F6C0.8090803@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The sample is useful for testing, and I'm using it. But after
loading the module, it keeps saying hi every 10 seconds, this may
be disturbing.

Also Steven said commenting out the "hi" helped in causing races. :)

[ Impact: make testing a bit easier ]
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A00F6AD.2070008@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

This patch adds code that can benchmark the ring buffer as well as
test it. This code can be compiled into the kernel (not recommended)
or as a module.

A separate ring buffer is used to not interfer with other users, like
ftrace. It creates a producer and a consumer (option to disable creation
of the consumer) and will run for 10 seconds, then sleep for 10 seconds
and then repeat.

While running, the producer will write 10 byte loads into the ring
buffer with just putting in the current CPU number. The reader will
continually try to read the buffer. The reader will alternate from reading
the buffer via event by event, or by full pages.

The output is a pr_info, thus it will fill up the syslogs.

  Starting ring buffer hammer
  End ring buffer hammer
  Time:     9000349 (usecs)
  Overruns: 12578640
  Read:     5358440  (by events)
  Entries:  0
  Total:    17937080
  Missed:   0
  Hit:      17937080
  Entries per millisec: 1993
  501 ns per entry
  Sleeping for 10 secs
  Starting ring buffer hammer
  End ring buffer hammer
  Time:     9936350 (usecs)
  Overruns: 0
  Read:     28146644  (by pages)
  Entries:  74
  Total:    28146718
  Missed:   0
  Hit:      28146718
  Entries per millisec: 2832
  353 ns per entry
  Sleeping for 10 secs

Time:      is the time the test ran
Overruns:  the number of events that were overwritten and not read
Read:      the number of events read (either by pages or events)
Entries:   the number of entries left in the buffer
                 (the by pages will only read full pages)
Total:     Entries + Read + Overruns
Missed:    the number of entries that failed to write
Hit:       the number of entries that were written

The above example shows that it takes ~353 nanosecs per entry when
there is a reader, reading by pages (and no overruns)

The event by event reader slowed the producer down to 501 nanosecs.

[ Impact: see how changes to the ring buffer affect stability and performance ]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

In the hot path of the ring buffer "__rb_reserve_next" there's a big
if statement that does not even return back to the work flow.

	code;

	if (cross to next page) {

		[ lots of code ]

		return;
	}

	more code;

The condition is even the unlikely path, although we do not denote it
with an unlikely because gcc is fine with it. The condition is true when
the write crosses a page boundary, and we need to start at a new page.

Having this if statement makes it hard to read, but calling another
function to do the work is also not appropriate, because we are using a lot
of variables that were set before the if statement, and we do not want to
send them as parameters.

This patch changes it to a goto:

	code;

	if (cross to next page)
		goto next_page;

	more code;

	return;

next_page:

	[ lots of code]

This makes the code easier to understand, and a bit more obvious.

The output from gcc is practically identical. For some reason, gcc decided
to use different registers when I switched it to a goto. But other than that,
the logic is the same.

[ Impact: easier to read code ]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

When adding the EXPORT_SYMBOL to some of the tracing API, I accidently
used EXPORT_SYMBOL instead of EXPORT_SYMBOL_GPL. This patch fixes
that mistake.

[ Impact: export the tracing code only for GPL modules ]
Reported-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The only references in the kernel to the .text.sched section are in
recordmcount.pl.  Since the code it has is intended to be example code
it should refer to real kernel sections.  So change it to .sched.text
instead.

[ Impact: consistency in comments ]
Signed-off-by: NTim Abbott <tabbott@mit.edu>
LKML-Reference: <1241136371-10768-1-git-send-email-tabbott@mit.edu>
Acked-by: NSam Ravnborg <sam@ravnborg.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

As a precaution, it is best to disable writing to the ring buffers
when reseting them.

[ Impact: prevent weird things if write happens during reset ]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

In the swap page ring buffer code that is used by the ftrace splice code,
we scan the page to increment the counter of entries read.

With the number of entries already in the page we simply need to add it.

[ Impact: speed up reading page from ring buffer ]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Currently, when the ring buffer writer overflows the buffer and must
write over non consumed data, we increment the overrun counter by
reading the entries on the page we are about to overwrite. This reads
the entries one by one.

This is not very effecient. This patch adds another entry counter
into each buffer page descriptor that keeps track of the number of
entries on the page. Now on overwrite, the overrun counter simply
needs to add the number of entries that is on the page it is about
to overwrite.

[ Impact: speed up of ring buffer in overwrite mode ]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The entries counter in cpu buffer is not atomic. It can be updated by
other interrupts or from another CPU (readers).

But making entries into "atomic_t" causes an atomic operation that can
hurt performance. Instead we convert it to a local_t that will increment
a counter with a local CPU atomic operation (if the arch supports it).

Instead of fighting with readers and overwrites that decrement the counter,
I added a "read" counter. Every time a reader reads an entry it is
incremented.

We already have a overrun counter and with that, the entries counter and
the read counter, we can calculate the total number of entries in the
buffer with:

  (entries - overrun) - read

As long as the total number of entries in the ring buffer is less than
the word size, this will work. But since the entries counter was previously
a long, this is no different than what we had before.

Thanks to Andrew Morton for pointing out in the first version that
atomic_t does not replace unsigned long. I switched to atomic_long_t
even though it is signed. A negative count is most likely a bug.

[ Impact: keep accurate count of cpu buffer entries ]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

This patch adds stats to the ftrace ring buffers:

 # cat /debugfs/tracing/per_cpu/cpu0/stats
 entries: 42360
 overrun: 30509326
 commit overrun: 0
 nmi dropped: 0

Where entries are the total number of data entries in the buffer.

overrun is the number of entries not consumed and were overwritten by
the writer.

commit overrun is the number of entries dropped due to nested writers
wrapping the buffer before the initial writer finished the commit.

nmi dropped is the number of entries dropped due to the ring buffer
lock being held when an nmi was going to write to the ring buffer.
Note, this field will be meaningless and will go away when the ring
buffer becomes lockless.

[ Impact: let userspace know what is happening in the ring buffers ]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The WARN_ON in the ring buffer when a commit is preempted and the
buffer is filled by preceding writes can happen in normal operations.
The WARN_ON makes it look like a bug, not to mention, because
it does not stop tracing and calls printk which can also recurse, this
is prone to deadlock (the WARN_ON is not in a position to recurse).

This patch removes the WARN_ON and replaces it with a counter that
can be retrieved by a tracer. This counter is called commit_overrun.

While at it, I added a nmi_dropped counter to count any time an NMI entry
is dropped because the NMI could not take the spinlock.

[ Impact: prevent deadlock by printing normal case warning ]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

I'm adding a module to do a series of tests on the ring buffer as well
as benchmarks. This module needs to have more of the ring buffer API
exported. There's nothing wrong with reading the ring buffer from a
module.

[ Impact: allow modules to read pages from the ring buffer ]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Document irqs for the newly created docbook.

[ Impact: add documentation ]
Signed-off-by: NJason Baron <jbaron@redhat.com>
Acked-by: NRandy Dunlap <randy.dunlap@oracle.com>
Cc: akpm@linux-foundation.org
Cc: rostedt@goodmis.org
Cc: fweisbec@gmail.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: wcohen@redhat.com
LKML-Reference: <73ff42be3420157667ec548e9b0e409c3cfad05f.1241107197.git.jbaron@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Add tracepoint docbook. This will help us document and understand
what tracepoints are in the kernel. Since there are multiple
macros, and files that contain tracepoints.

[ Impact: add documentation ]
Signed-off-by: NJason Baron <jbaron@redhat.com>
Acked-by: NRandy Dunlap <randy.dunlap@oracle.com>
Cc: akpm@linux-foundation.org
Cc: rostedt@goodmis.org
Cc: fweisbec@gmail.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: wcohen@redhat.com
LKML-Reference: <84160b6bd94aff02455da7e12bad054d34c579a0.1241107197.git.jbaron@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Add support to kernel-doc for tracepoint comments above TRACE_EVENT()
macro definitions. Paves the way for tracepoint docbook.

[ Impact: extend DocBook infrastructure ]
Signed-off-by: NJason Baron <jbaron@redhat.com>
Acked-by: NRandy Dunlap <randy.dunlap@oracle.com>
Cc: akpm@linux-foundation.org
Cc: rostedt@goodmis.org
Cc: fweisbec@gmail.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: wcohen@redhat.com
LKML-Reference: <d80706b6797e277924d2f3ec9af176c6b2951f88.1241107197.git.jbaron@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

"tracing: create automated trace defines" causes this compile error on s390,
as reported by Sachin Sant against linux-next:

 kernel/built-in.o: In function `__do_softirq':
 (.text+0x1c680): undefined reference to `__tracepoint_softirq_entry'

This happens because the definitions of the softirq tracepoints were moved
from kernel/softirq.c to kernel/irq/handle.c. Since s390 doesn't support
generic hardirqs handle.c doesn't get compiled and the definitions are
missing.

So move the tracepoints to softirq.c again.

[ Impact: fix build failure on s390 ]
Reported-by: NSachin Sant <sachinp@in.ibm.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: fweisbec@gmail.com
LKML-Reference: <20090429135139.5fac79b8@osiris.boeblingen.de.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Replace the current event parser hack with a better one.  Filters are
no longer specified predicate by predicate, but all at once and can
use parens and any of the following operators:

numeric fields:

==, !=, <, <=, >, >=

string fields:

==, !=

predicates can be combined with the logical operators:

&&, ||

examples:

"common_preempt_count > 4" > filter

"((sig >= 10 && sig < 15) || sig == 17) && comm != bash" > filter

If there was an error, the erroneous string along with an error
message can be seen by looking at the filter e.g.:

((sig >= 10 && sig < 15) || dsig == 17) && comm != bash
^
parse_error: Field not found

Currently the caret for an error always appears at the beginning of
the filter; a real position should be used, but the error message
should be useful even without it.

To clear a filter, '0' can be written to the filter file.

Filters can also be set or cleared for a complete subsystem by writing
the same filter as would be written to an individual event to the
filter file at the root of the subsytem.  Note however, that if any
event in the subsystem lacks a field specified in the filter being
set, the set will fail and all filters in the subsytem are
automatically cleared.  This change from the previous version was made
because using only the fields that happen to exist for a given event
would most likely result in a meaningless filter.

Because the logical operators are now implemented as predicates, the
maximum number of predicates in a filter was increased from 8 to 16.

[ Impact: add new, extended trace-filter implementation ]
Signed-off-by: NTom Zanussi <tzanussi@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: fweisbec@gmail.com
Cc: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <1240905899.6416.121.camel@tropicana>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The new filter comparison ops need to be able to distinguish between
signed and unsigned field types, so add an is_signed flag/param to the
event field struct/trace_define_fields().  Also define a simple macro,
is_signed_type() to determine the signedness at compile time, used in the
trace macros.  If the is_signed_type() macro won't work with a specific
type, a new slightly modified version of TRACE_FIELD() called
TRACE_FIELD_SIGN(), allows the signedness to be set explicitly.

[ Impact: extend trace-filter code for new feature ]
Signed-off-by: NTom Zanussi <tzanussi@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: fweisbec@gmail.com
Cc: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <1240905893.6416.120.camel@tropicana>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Create a new event_filter object, and move the pred-related members
out of the call and subsystem objects and into the filter object - the
details of the filter implementation don't need to be exposed in the
call and subsystem in any case, and it will also help make the new
parser implementation a little cleaner.

[ Impact: refactor trace-filter code to prepare for new features ]
Signed-off-by: NTom Zanussi <tzanussi@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: fweisbec@gmail.com
Cc: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <1240905887.6416.119.camel@tropicana>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Follow up to afcfe024 in Linus' tree
("x86: mmiotrace: quieten spurious warning message")
Signed-off-by: NStuart Bennett <stuart@freedesktop.org>
Acked-by: NPekka Paalanen <pq@iki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1240946271-7083-5-git-send-email-stuart@freedesktop.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

* 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: NStuart Bennett <stuart@freedesktop.org>
Acked-by: NPekka Paalanen <pq@iki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1240946271-7083-4-git-send-email-stuart@freedesktop.org>
Signed-off-by: NIngo 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: NStuart Bennett <stuart@freedesktop.org>
Acked-by: NPekka Paalanen <pq@iki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1240946271-7083-3-git-send-email-stuart@freedesktop.org>
Signed-off-by: NIngo 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: NSteven 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: NSteven 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: NSteven 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: NSteven Rostedt <rostedt@goodmis.org>