Impact: tracer output improvement

Ending newlines are appended automatically on comments by the function
graph tracer because the newline needs to be placed after the "*/"
comment characters.

So if the user puts an ending newline, we want to strip it.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: extend the wakeup tracepoint with the info whether the wakeup was real

Add the information needed to distinguish 'real' wakeups from 'false'
wakeups.
Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: eliminate false WARN_ON message

If an interrupt goes off after the setting of the local variable
tail_page and before incrementing the write index of that page,
the interrupt could push the commit forward to the next page.

Later a check is made to see if interrupts pushed the buffer around
the entire ring buffer by comparing the next page to the last commited
page. This can produce a false positive if the interrupt had pushed
the commit page forward as stated above.

Thanks to Jiaying Zhang for finding this race.
Reported-by: NJiaying Zhang <jiayingz@google.com>
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix stuck trace-buffers

If an interrupt comes in during the rb_set_commit_to_write and
pushes the tail page forward just at the right time, the commit
updates will miss the adding of the interrupt data. This will
cause the commit pointer to cease from moving forward.

Thanks to Jiaying Zhang for finding this race.
Reported-by: NJiaying Zhang <jiayingz@google.com>
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: cleanup

This patch factors out common code from multiple tracers into a
tracing_reset_online_cpus() function and converts the tracers to use it.
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

these warnings:

  kernel/trace/trace_sched_switch.c: In function ‘tracing_sched_register’:
  kernel/trace/trace_sched_switch.c:96: warning: passing argument 1 of ‘register_trace_sched_wakeup_new’ from incompatible pointer type
  kernel/trace/trace_sched_switch.c:112: warning: passing argument 1 of ‘unregister_trace_sched_wakeup_new’ from incompatible pointer type
  kernel/trace/trace_sched_switch.c: In function ‘tracing_sched_unregister’:
  kernel/trace/trace_sched_switch.c:121: warning: passing argument 1 of ‘unregister_trace_sched_wakeup_new’ from incompatible pointer type

Trigger because sched_wakeup_new tracepoints need the same trace
signature as sched_wakeup - which was changed recently.

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

this warning:

  kernel/trace/trace.c: In function ‘print_lat_fmt’:
  kernel/trace/trace.c:1826: warning: unused variable ‘state’

Triggers because 'state' has become unused - remove it.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: remove dead code

struct ring_buffer.size is not set after ring_buffer is initialized
or resized. it is always 0.

we can use "buffer->pages * PAGE_SIZE" to get ring_buffer's size
Signed-off-by: NLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix occasionally incorrect trace output

The tracing code has interesting varieties of printing out task state.

Unfortunalely only one of the instances is correct as it copies the
code from sched.c:sched_show_task(). The others are plain wrong as
they treatthe bitfield as an integer offset into the character
array. Also the size check of the character array is wrong as it
includes the trailing \0.

Use a common state decoder inline which does the Right Thing.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: enhancement

Ingo Molnar has asked about a way to remove items from the filter
lists. Currently, you can only add or replace items. The way
items are added to the list is through opening one of the list
files (set_ftrace_filter or set_ftrace_notrace) via append.
If the file is opened for truncate, the list is cleared.

  echo spin_lock > /debug/tracing/set_ftrace_filter

The above will replace the list with only spin_lock

  echo spin_lock >> /debug/tracing/set_ftrace_filter

The above will add spin_lock to the list.

Now this patch adds:

  echo '!spin_lock' >> /debug/tracing/set_ftrace_filter

This will remove spin_lock from the list.

The limited glob features of these lists also can be notted.

  echo '!spin_*' >> /debug/tracing/set_ftrace_filter

This will remove all functions that start with 'spin_'

Note:

  echo '!spin_*' > /debug/tracing/set_ftrace_filter

will simply clear out the list (notice the '>' instead of '>>')
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: clean up

Andrew Morton suggested to use the stack_tracer_enabled variable
to decide whether or not to start stack tracing on bootup.
This lets us remove the start_stack_trace variable.
Reported-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: enhancement to stack tracer

The stack tracer currently is either on when configured in or
off when it is not. It can not be disabled when it is configured on.
(besides disabling the function tracer that it uses)

This patch adds a way to enable or disable the stack tracer at
run time. It defaults off on bootup, but a kernel parameter 'stacktrace'
has been added to enable it on bootup.

A new sysctl has been added "kernel.stack_tracer_enabled" to let
the user enable or disable the stack tracer at run time.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: display ftrace_printk messages "as is"

By default, ftrace_printk() messages find their output with some other
informations like pid, caller, ...
Sometimes a developer just want to have the ftrace_printk left "as is", without
other information.

This is done by providing a default-off option called printk-msg-only.
To enable it, just do `echo printk-msg-only > /debugfs/tracing/trace_options`

Before the patch:

           <...>-2739  [000]   145.692153: __might_sleep: I'm an ftrace_printk msg in __might_sleep
           <...>-2739  [000]   145.692155: __might_sleep: I'm another ftrace_printk msg in __might_sleep

After the patch and the printk-msg-only option enabled:

I'm an ftrace_printk msg in __might_sleep
I'm another ftrace_printk msg in __might_sleep
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: prevent a trace recursion

After some tests with function graph tracer under x86-32, I saw some recursions
caused by ring_buffer_time_stamp() that calls preempt_enable_no_notrace() which
calls preempt_schedule() which is traced itself.

This patch re-enables preemption without rescheduling.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: make more obvious the hardirq calls in the output

When a hardirq is triggered inside the codeflow on output, we have
now two arrows that indicate the entry and return of the hardirq.

 0)               |          bit_waitqueue() {
 0)   0.880 us    |            __phys_addr();
 0)   2.699 us    |          }
 0)               |          __wake_up_bit() {
 0)   ==========> |          smp_apic_timer_interrupt() {
 0)   0.797 us    |            native_apic_mem_write();
 0)   0.715 us    |            exit_idle();
 0)               |            irq_enter() {
 0)   0.722 us    |              idle_cpu();
 0)   5.519 us    |            }
 0)               |            hrtimer_interrupt() {
 0)               |              ktime_get() {
 0)               |                ktime_get_ts() {
 0)   0.805 us    |                  getnstimeofday();

 [...]

 0) ! 108.528 us  |            }
 0)               |            irq_exit() {
 0)               |              do_softirq() {
 0)               |                __do_softirq() {
 0)   0.895 us    |                  __local_bh_disable();
 0)               |                  run_timer_softirq() {
 0)   0.827 us    |                    hrtimer_run_pending();
 0)   1.226 us    |                    _spin_lock_irq();
 0)               |                    _spin_unlock_irq() {
 0)   6.550 us    |                  }
 0)   0.924 us    |                  _local_bh_enable();
 0) + 12.129 us   |                }
 0) + 13.911 us   |              }
 0)   0.707 us    |              idle_cpu();
 0) + 17.009 us   |            }
 0) ! 137.419 us  |          }
 0)   <========== |
 0)   1.045 us    |          }
 0) ! 148.908 us  |        }
 0) ! 151.022 us  |      }
 0) ! 153.022 us  |    }
 0)   0.963 us    |    journal_mark_dirty();
 0)   0.925 us    |    __brelse();
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: restructure code, cleanup

Remove BTS bits from the hw-branch-tracer (renamed from bts-tracer) and
use the ds interface.
Signed-off-by: NMarkus Metzger <markut.t.metzger@intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

this warning:

 kernel/trace/trace.c: In function ‘trace_vprintk’:
 kernel/trace/trace.c:3626: warning: ‘flags’ may be used uninitialized in this function

shows some confusion about irq_flags / flags use here. We already have
irq_flags so remove the extra flags variable.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: Provide a way to pause the function graph tracer

As suggested by Steven Rostedt, the previous patch that prevented from
spinlock function tracing shouldn't use the raw_spinlock to fix it.
It's much better to follow lockdep with normal spinlock, so this patch
adds a new flag for each task to make the function graph tracer able
to be paused. We also can send an ftrace_printk whithout worrying of
the irrelevant traced spinlock during insertion.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: cleanup

Apply some suggestions of Steven Rostedt:

_turn tracing_selftest_running into a simple int (no need of an atomic_t)
_set it __read_mostly
_fix a comment style
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: provide trace headers to explain a bit the output

This patch implements the print_headers callback for the function graph
tracer. These headers are output according to the current trace options.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: clean up

Using (struct pid *)-1 as the pointer for ftrace_swapper_pid is
a little confusing for others. This patch uses the address of the
actual init pid structure instead. This change is only for
clarity. It does not affect the code itself. Hopefully soon the
swapper tasks will all have their own pid structure and then
we can clean up the code a bit more.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: cleanup

As suggested by Steven Rostedt, this patch provide a new macro
task_curr_ret_stack() to move the cpp conditionnal CONFIG into
the linux/ftrace.h headers.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix default empty traces on function-graph-tracer

The actual ftrace_trace_task() checks if ftrace_pid_trace is allocated
and return 1 if it is true.
If it is NULL, it will check the bit of pid tracing flag for the current
task (which are not set by default).
So by default, a task is not traced.
Actually all tasks should be traced by default and filter_by_pid when
ftrace_pid_trace is allocated.

The appropriate condition should be to return 1 if filter_by_pid is
set.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acke-dby: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix tracer selfstests false results

After setting a ftrace_printk somewhere in th kernel, I saw the
Function tracer selftest failing.

When a selftest occurs, the ring buffer is lurked to see if
some entries were inserted. But concurrent insertion such as
ftrace_printk could occured at the same time and could give
false positive or negative results.

This patch prevent prevent from TRACE_PRINT entries insertion
during selftests.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Handle the TRACE_PRINT entries from the function grapg tracer
and output them as a C comment just below the function that called
it, as if it was a comment inside this function.

Example with an ftrace_printk inside might_sleep() function:

void __might_sleep(char *file, int line)
{
	static unsigned long prev_jiffy;	/* ratelimiting */

	ftrace_printk("Hi I'm a comment in might_sleep() :-)");

A chunk of a resulting trace:

 0)               |        _reiserfs_free_block() {
 0)               |          reiserfs_read_bitmap_block() {
 0)               |            __bread() {
 0)               |              __getblk() {
 0)               |                __find_get_block() {
 0)   0.698 us    |                  mark_page_accessed();
 0)   2.267 us    |                }
 0)               |                __might_sleep() {
 0)               |                  /* Hi I'm a comment in might_sleep() :-) */
 0)   1.321 us    |                }
 0)   5.872 us    |              }
 0)   7.313 us    |            }
 0)   8.718 us    |          }

And this patch brings two minor fixes:

- The newline after a switch-out task has disappeared
- The "|" sign just before the cpu number on task-switch has been deleted.

 0)   0.616 us    |                pick_next_task_rt();
 0)   1.457 us    |                _spin_trylock();
 0)   0.653 us    |                _spin_unlock();
 0)   0.728 us    |                _spin_trylock();
 0)   0.631 us    |                _spin_unlock();
 0)   0.729 us    |                native_load_sp0();
 0)   0.593 us    |                native_load_tls();
 ------------------------------------------
 0)    cat-2834    =>   migrati-3
 ------------------------------------------

 0)               |    finish_task_switch() {
 0)   0.841 us    |      _spin_unlock_irq();
 0)   0.616 us    |      post_schedule_rt();
 0)   3.882 us    |    }
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix a bug in function filter setting

when writing function to set_graph_function, we should check whether it
has existed in set_graph_function to avoid duplicating.
Signed-off-by: NLiming Wang <liming.wang@windriver.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix build bugs
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: new feature

This patch lets the swapper tasks of all CPUS be filtered by the
set_ftrace_pid file.

If '0' is echoed into this file, then all the idle tasks (aka swapper)
is flagged to be traced.  This affects all CPU idle tasks.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: clean up, extend PID filtering to PID namespaces

Eric Biederman suggested using the struct pid for filtering on
pids in the kernel. This patch is based off of a demonstration
of an implementation that Eric sent me in an email.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: New feature

This patch makes the changes to set_ftrace_pid apply to the function
graph tracer.

  # echo $$ > /debugfs/tracing/set_ftrace_pid
  # echo function_graph > /debugfs/tracing/current_tracer

Will cause only the current task to be traced. Note, the trace flags are
also inherited by child processes, so the children of the shell
will also be traced.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: clean up

Use the new task struct trace flags to determine if a process should be
traced or not.

Note: this moves the searching of the pid to the slow path of setting
the pid field. This needs to be converted to the pid name space.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

This patch adds the file:

   /debugfs/tracing/set_graph_function

which can be used along with the function graph tracer.

When this file is empty, the function graph tracer will act as
usual. When the file has a function in it, the function graph
tracer will only trace that function.

For example:

 # echo blk_unplug > /debugfs/tracing/set_graph_function
 # cat /debugfs/tracing/trace
 [...]
 ------------------------------------------
 | 2)  make-19003  =>  kjournald-2219
 ------------------------------------------

 2)               |  blk_unplug() {
 2)               |    dm_unplug_all() {
 2)               |      dm_get_table() {
 2)      1.381 us |        _read_lock();
 2)      0.911 us |        dm_table_get();
 2)      1. 76 us |        _read_unlock();
 2) +   12.912 us |      }
 2)               |      dm_table_unplug_all() {
 2)               |        blk_unplug() {
 2)      0.778 us |          generic_unplug_device();
 2)      2.409 us |        }
 2)      5.992 us |      }
 2)      0.813 us |      dm_table_put();
 2) +   29. 90 us |    }
 2) +   34.532 us |  }

You can add up to 32 functions into this file. Currently we limit it
to 32, but this may change with later improvements.

To add another function, use the append '>>':

  # echo sys_read >> /debugfs/tracing/set_graph_function
  # cat /debugfs/tracing/set_graph_function
  blk_unplug
  sys_read

Using the '>' will clear out the function and write anew:

  # echo sys_write > /debug/tracing/set_graph_function
  # cat /debug/tracing/set_graph_function
  sys_write

Note, if you have function graph running while doing this, the small
time between clearing it and updating it will cause the graph to
record all functions. This should not be an issue because after
it sets the filter, only those functions will be recorded from then on.
If you need to only record a particular function then set this
file first before starting the function graph tracer. In the future
this side effect may be corrected.

The set_graph_function file is similar to the set_ftrace_filter but
it does not take wild cards nor does it allow for more than one
function to be set with a single write. There is no technical reason why
this is the case, I just do not have the time yet to implement that.

Note, dynamic ftrace must be enabled for this to appear because it
uses the dynamic ftrace records to match the name to the mcount
call sites.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix to output of stack trace

If a function is not found in the stack of the stack tracer, the
number printed is quite strange. This fixes the algorithm to handle
missing functions better.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

CONFIG_FUNCTION_GRAPH_TRACER depends on FUNCTION_TRACER already,
(turning it non-default) so it so making it default-n is pointless.

So enable it by default - it's a nice extension of the function tracer.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: better trace output of duration for long calls

The old duration output didn't exceeded 9999.999 us to fit the column
and the nanosecs were always 3 numbers. As Ingo suggested, it's better
to have the whole microseconds elapsed time and shift the nanosecs precision
if needed to fit the maximum 7 numbers. And usec need more number, the case
should be rare and important enough to break a bit the column alignment to
show it.

So, depending of the duration value, we now have these patterns:

    u.nnn us
   uu.nnn us
  uuu.nnn us
 uuuu.nnn us
 uuuuu.nn us
 uuuuuu.n us
 uuuuuuuu..... us
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: extend function-graph output: let one know which thread called a function

This patch implements a helper function to print the couple cmdline/pid.
Its output is provided during task switching and on each row if the new
"funcgraph-proc" defualt-off option is set through trace_options file.

The output is center aligned and never exceeds 14 characters. The cmdline
is truncated over 7 chars.
But note that if the pid exceeds 6 characters, the column will overflow (but
the situation is abnormal).
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: feature, let entry function decide to trace or not

This patch lets the graph tracer entry function decide if the tracing
should be done at the end as well. This requires all function graph
entry functions return 1 if it should trace, or 0 if the return should
not be traced.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: clean up

Andrew Morton pointed out that the kernel convention of a variable
named page should be of type page struct. The ring buffer uses
a variable named "page" for a pointer to something else.

This patch converts those to be called "bpage" (as in "buffer page").
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: new ftrace_graph_stop function

While developing more features of function graph, I hit a bug that
caused the WARN_ON to trigger in the prepare_ftrace_return function.
Well, it was hard for me to find out that was happening because the
bug would not print, it would just cause a hard lockup or reboot.
The reason is that it is not safe to call printk from this function.

Looking further, I also found that it calls unregister_ftrace_graph,
which grabs a mutex and calls kstop machine. This would definitely
lock the box up if it were to trigger.

This patch adds a fast and safe ftrace_graph_stop() which will
stop the function tracer. Then it is safe to call the WARN ON.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: new API to ring buffer

This patch adds a new interface into the ring buffer that allows a
page to be read from the ring buffer on a given CPU. For every page
read, one must also be given to allow for a "swap" of the pages.

 rpage = ring_buffer_alloc_read_page(buffer);
 if (!rpage)
	goto err;
 ret = ring_buffer_read_page(buffer, &rpage, cpu, full);
 if (!ret)
	goto empty;
 process_page(rpage);
 ring_buffer_free_read_page(rpage);

The caller of these functions must handle any waits that are
needed to wait for new data. The ring_buffer_read_page will simply
return 0 if there is no data, or if "full" is set and the writer
is still on the current page.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>