linux-toradex.git/kernel/trace/trace_uprobe.c, branch v4.0-rc1

Merge tag 'trace-v3.20' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

2015-02-12T16:37:41+00:00

Pull tracing updates from Steven Rostedt:
 "The updates included in this pull request for ftrace are:

   o Several clean ups to the code

     One such clean up was to convert to 64 bit time keeping, in the
     ring buffer benchmark code.

   o Adding of __print_array() helper macro for TRACE_EVENT()

   o Updating the sample/trace_events/ to add samples of different ways
     to make trace events.  Lots of features have been added since the
     sample code was made, and these features are mostly unknown.
     Developers have been making their own hacks to do things that are
     already available.

   o Performance improvements.  Most notably, I found a performance bug
     where a waiter that is waiting for a full page from the ring buffer
     will see that a full page is not available, and go to sleep.  The
     sched event caused by it going to sleep would cause it to wake up
     again.  It would see that there was still not a full page, and go
     back to sleep again, and that would wake it up again, until finally
     it would see a full page.  This change has been marked for stable.

  Other improvements include removing global locks from fast paths"

* tag 'trace-v3.20' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  ring-buffer: Do not wake up a splice waiter when page is not full
  tracing: Fix unmapping loop in tracing_mark_write
  tracing: Add samples of DECLARE_EVENT_CLASS() and DEFINE_EVENT()
  tracing: Add TRACE_EVENT_FN example
  tracing: Add TRACE_EVENT_CONDITION sample
  tracing: Update the TRACE_EVENT fields available in the sample code
  tracing: Separate out initializing top level dir from instances
  tracing: Make tracing_init_dentry_tr() static
  trace: Use 64-bit timekeeping
  tracing: Add array printing helper
  tracing: Remove newline from trace_printk warning banner
  tracing: Use IS_ERR() check for return value of tracing_init_dentry()
  tracing: Remove unneeded includes of debugfs.h and fs.h
  tracing: Remove taking of trace_types_lock in pipe files
  tracing: Add ref count to tracer for when they are being read by pipe

tracing: Use IS_ERR() check for return value of tracing_init_dentry()

2015-01-22T16:19:49+00:00

tracing_init_dentry() will soon return NULL as a valid pointer for the
top level tracing directroy. NULL can not be used as an error value.
Instead, switch to ERR_PTR() and check the return status with
IS_ERR().

Signed-off-by: Steven Rostedt

perf: Avoid horrible stack usage

2015-01-14T14:11:45+00:00

Both Linus (most recent) and Steve (a while ago) reported that perf
related callbacks have massive stack bloat.

The problem is that software events need a pt_regs in order to
properly report the event location and unwind stack. And because we
could not assume one was present we allocated one on stack and filled
it with minimal bits required for operation.

Now, pt_regs is quite large, so this is undesirable. Furthermore it
turns out that most sites actually have a pt_regs pointer available,
making this even more onerous, as the stack space is pointless waste.

This patch addresses the problem by observing that software events
have well defined nesting semantics, therefore we can use static
per-cpu storage instead of on-stack.

Linus made the further observation that all but the scheduler callers
of perf_sw_event() have a pt_regs available, so we change the regular
perf_sw_event() to require a valid pt_regs (where it used to be
optional) and add perf_sw_event_sched() for the scheduler.

We have a scheduler specific call instead of a more generic _noregs()
like construct because we can assume non-recursion from the scheduler
and thereby simplify the code further (_noregs would have to put the
recursion context call inline in order to assertain which __perf_regs
element to use).

One last note on the implementation of perf_trace_buf_prepare(); we
allow .regs = NULL for those cases where we already have a pt_regs
pointer available and do not need another.

Reported-by: Linus Torvalds 
Reported-by: Steven Rostedt 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Arnaldo Carvalho de Melo 
Cc: Javi Merino 
Cc: Linus Torvalds 
Cc: Mathieu Desnoyers 
Cc: Oleg Nesterov 
Cc: Paul Mackerras 
Cc: Petr Mladek 
Cc: Steven Rostedt 
Cc: Tom Zanussi 
Cc: Vaibhav Nagarnaik 
Link: http://lkml.kernel.org/r/20141216115041.GW3337@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar

tracing: Deletion of an unnecessary check before iput()

2014-11-19T21:28:45+00:00

The iput() function tests whether its argument is NULL and then
returns immediately. Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.

Link: http://lkml.kernel.org/r/5468F875.7080907@users.sourceforge.net

Signed-off-by: Markus Elfring 
Signed-off-by: Steven Rostedt

tracing/uprobes: Do not use return values of trace_seq_printf()

2014-11-19T20:25:45+00:00

The functions trace_seq_printf() and friends will soon no longer have
return values. Using trace_seq_has_overflowed() and trace_handle_return()
should be used instead.

Link: http://lkml.kernel.org/r/20141114011411.693008134@goodmis.org
Link: http://lkml.kernel.org/r/20141115050602.333705855@goodmis.org

Reviewed-by: Masami Hiramatsu 
Acked-by: Srikar Dronamraju 
Acked-by: Namhyung Kim 
Signed-off-by: Steven Rostedt

trace: Replace single-character seq_puts with seq_putc

2014-11-14T12:55:55+00:00

Printing a single character to a seqfile might as well be done with
seq_putc instead of seq_puts; this avoids a strlen() call and a memory
access. It also shaves another few bytes off the generated code.

Link: http://lkml.kernel.org/r/1415479332-25944-4-git-send-email-linux@rasmusvillemoes.dk

Signed-off-by: Rasmus Villemoes 
Signed-off-by: Steven Rostedt

tracing: Replace seq_printf by simpler equivalents

2014-11-14T02:32:19+00:00

Using seq_printf to print a simple string or a single character is a
lot more expensive than it needs to be, since seq_puts and seq_putc
exist.

These patches do

  seq_printf(m, s) -> seq_puts(m, s)
  seq_printf(m, "%s", s) -> seq_puts(m, s)
  seq_printf(m, "%c", c) -> seq_putc(m, c)

Subsequent patches will simplify further.

Link: http://lkml.kernel.org/r/1415479332-25944-2-git-send-email-linux@rasmusvillemoes.dk

Signed-off-by: Rasmus Villemoes 
Signed-off-by: Steven Rostedt

tracing/uprobes: Kill the dead TRACE_EVENT_FL_USE_CALL_FILTER logic

2014-07-16T18:25:19+00:00

alloc_trace_uprobe() sets TRACE_EVENT_FL_USE_CALL_FILTER for unknown
reason and this is simply wrong. Fortunately this has no effect because
register_uprobe_event() clears call->flags after that.

Kill both. This trace_uprobe was kzalloc'ed and we rely on this fact
anyway.

Link: http://lkml.kernel.org/p/20140715184824.GA20505@redhat.com

Signed-off-by: Oleg Nesterov 
Acked-by: Srikar Dronamraju 
Signed-off-by: Steven Rostedt

tracing/uprobes: Fix the usage of uprobe_buffer_enable() in probe_event_enable()

2014-06-30T17:22:33+00:00

The usage of uprobe_buffer_enable() added by dcad1a20 is very wrong,

1. uprobe_buffer_enable() and uprobe_buffer_disable() are not balanced,
   _enable() should be called only if !enabled.

2. If uprobe_buffer_enable() fails probe_event_enable() should clear
   tp.flags and free event_file_link.

3. If uprobe_register() fails it should do uprobe_buffer_disable().

Link: http://lkml.kernel.org/p/20140627170146.GA18332@redhat.com

Acked-by: Namhyung Kim 
Acked-by: Srikar Dronamraju 
Reviewed-by: Masami Hiramatsu 
Fixes: dcad1a204f72 "tracing/uprobes: Fetch args before reserving a ring buffer"
Signed-off-by: Oleg Nesterov 
Signed-off-by: Steven Rostedt

tracing/uprobes: Kill the bogus UPROBE_HANDLER_REMOVE code in uprobe_dispatcher()

2014-06-30T17:22:23+00:00

I do not know why dd9fa555d7bb "tracing/uprobes: Move argument fetching
to uprobe_dispatcher()" added the UPROBE_HANDLER_REMOVE, but it looks
wrong.

OK, perhaps it makes sense to avoid store_trace_args() if the tracee is
nacked by uprobe_perf_filter(). But then we should kill the same code
in uprobe_perf_func() and unify the TRACE/PROFILE filtering (we need to
do this anyway to mix perf/ftrace). Until then this code actually adds
the pessimization because uprobe_perf_filter() will be called twice and
return T in likely case.

Link: http://lkml.kernel.org/p/20140627170143.GA18329@redhat.com

Acked-by: Namhyung Kim 
Acked-by: Srikar Dronamraju 
Signed-off-by: Oleg Nesterov 
Signed-off-by: Steven Rostedt