Every time we cat a trace_stat file, we leak memory allocated by
seq_open().

Also fix memory leak in a failure path in tracing_stat_open().

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A67D92B.4060704@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

It's wrong to increment @pos in stat_seq_start(). It causes some
stat entries lost when reading stat file, if the output of the file
is larger than PAGE_SIZE.

Reviewed-by: Liming Wang <liming.wang@windriver.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A418716.90209@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

register_stat_tracer() uses list_for_each_entry_safe
to check whether a tracer is already present in the list.
But we don't delete anything from the list here, so
we don't need the safe version

[ Impact: cleanup list use is stat tracing ]

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

- remove duplicate code in stat_seq_init()
- update comments to reflect the change from stat list to stat rbtree

[ Impact: clean up ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

When closing a trace_stat file, we destroy the rbtree constructed during
file open, but there is memory leak that the root node is not freed.

[ Impact: fix memory leak when closing a trace_stat file ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

Currently the output of trace_stat/workqueues is totally reversed:

 # cat /debug/tracing/trace_stat/workqueues
    ...
    1       17       17      210       37   `-blk_unplug_work+0x0/0x57
    1     3779     3779      181       11   |-cfq_kick_queue+0x0/0x2f
    1     3796     3796                     kblockd/1:120
    ...

The correct output should be:

    1     3796     3796                     kblockd/1:120
    1     3779     3779      181       11   |-cfq_kick_queue+0x0/0x2f
    1       17       17      210       37   `-blk_unplug_work+0x0/0x57

It's caused by "tracing/stat: replace linked list by an rbtree for
sorting"
(53059c9b67a62a3dc8c80204d3da42b9267ea5a0).

dummpy_cmp() should return -1, so rb_node will always be inserted as
right-most node in the rbtree, thus we sort the output in ascending
order.

[ Impact: fix the output of trace_stat/workqueues ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

When the stat tracing framework prepares the entries from a tracer
to output them to the user, it starts by computing a linear sort
through a linked list to give the entries ordered by relevance
to the user.

This is quite ugly and causes a small latency when we begin to
read the file.

This patch changes that by turning the linked list into a red-black
tree. Athough the whole iteration using the start and next tracer
callbacks while opening the file remain the same, it is now much
more fast and scalable.

The rbtree guarantees O(log(n)) insertions whereas a linked
list with linear sorting brought us a O(n) despair. Now the
(visible) latency has disapeared.

[ Impact: kill the latency while starting to read a stat tracer file ]

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

The "trace" prefix in struct trace_stat_session type is annoying while
reading the trace_stat.c file. It makes the lines longer, and
is not that much useful to explain the sense of this type.

Just keep "struct stat_session" for this type.

[ Impact: make the code a bit more readable ]

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

Merge reason: update to upstream tracing facilities

Signed-off-by: Ingo Molnar <mingo@elte.hu>

Impact: make trace_stat files show items with the original order

trace_stat tracer reverse the items, it makes the output
looks a little ugly.

Example, when we read trace_stat/workqueues, we get cpu#7's stat.
at first, and then cpu#6... cpu#0.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <49C9F23F.5040307@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>