If the seq_read fills the buffer it will call s_start again on the next
itertation with the same position. This causes a problem with the
function_graph tracer because it consumes the iteration in order to
determine leaf functions.

What happens is that the iterator stores the entry, and the function
graph plugin will look at the next entry. If that next entry is a return
of the same function and task, then the function is a leaf and the
function_graph plugin calls ring_buffer_read which moves the ring buffer
iterator forward (the trace iterator still points to the function start
entry).

The copying of the trace_seq to the seq_file buffer will fail if the
seq_file buffer is full. The seq_read will not show this entry.
The next read by userspace will cause seq_read to again call s_start
which will reuse the trace iterator entry (the function start entry).
But the function return entry was already consumed. The function graph
plugin will think that this entry is a nested function and not a leaf.

To solve this, the trace code now checks the return status of the
seq_printf (trace_print_seq). If the writing to the seq_file buffer
fails, we set a flag in the iterator (leftover) and we do not reset
the trace_seq buffer. On the next call to s_start, we check the leftover
flag, and if it is set, we just reuse the trace_seq buffer and do not
call into the plugin print functions.

Before this patch:

 2)               |      fput() {
 2)               |        __fput() {
 2)   0.550 us    |          inotify_inode_queue_event();
 2)               |          __fsnotify_parent() {
 2)   0.540 us    |          inotify_dentry_parent_queue_event();

After the patch:

 2)               |      fput() {
 2)               |        __fput() {
 2)   0.550 us    |          inotify_inode_queue_event();
 2)   0.548 us    |          __fsnotify_parent();
 2)   0.540 us    |          inotify_dentry_parent_queue_event();

[
  Updated the patch to fix a missing return 0 from the trace_print_seq()
  stub when CONFIG_TRACING is disabled.
Reported-by: NIngo Molnar <mingo@elte.hu>
]
Reported-by: NJiri Olsa <jolsa@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The cpu argument is not used inside the rb_time_stamp() function.
Plus fix a typo.
Signed-off-by: NJiri Olsa <jolsa@redhat.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20091023233647.118547500@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

when compiling linux-mips with kmemtrace enabled, there will be an
error:

include/linux/trace_seq.h:12: error: 'PAGE_SIZE' undeclared here (not in
				a function)

I checked the source code and found trace_seq.h used PAGE_SIZE but not
included the relative header file, so, fix it via adding the header file
<asm/page.h>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NWu Zhangjin <wuzj@lemote.com>
LKML-Reference: <1244962350-28702-1-git-send-email-wuzhangjin@gmail.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The code to update the print formats for events requires a vprintf
format in the trace_seq. This patch adds that interface.
Signed-off-by: NSteven 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: NSteven Rostedt <rostedt@goodmis.org>

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

Impact: allow modules to add TRACE_EVENTS on load

This patch adds the final hooks to allow modules to use the TRACE_EVENT
macro. A notifier and a data structure are used to link the TRACE_EVENTs
defined in the module to connect them with the ftrace event tracing system.

It also adds the necessary automated clean ups to the trace events when a
module is removed.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

In the process to make TRACE_EVENT macro work for modules, the trace_seq
operations must be available for core kernel code.

These operations are quite useful and can be used for other implementations.

The main idea is that we create a trace_seq handle that acts very much
like the seq_file handle.

	struct trace_seq *s = kmalloc(sizeof(*s, GFP_KERNEL);

	trace_seq_init(s);
	trace_seq_printf(s, "some data %d\n", variable);

	printk("%s", s->buffer);

The main use is to allow a top level function call several other functions
that may store printf like data into the buffer. Then at the end, the top
level function can process all the data with any method it would like to.
It could be passed to userspace, output via printk or even use seq_file:

	trace_seq_to_user(s, ubuf, cnt);
	seq_puts(m, s->buffer);
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>