linux-toradex.git/kernel/tracepoint.c, branch v2.6.39-rc7

tracepoints: Fix section alignment using pointer array

2011-02-03T14:28:46+00:00

Make the tracepoints more robust, making them solid enough to handle compiler
changes by not relying on anything based on compiler-specific behavior with
respect to structure alignment. Implement an approach proposed by David Miller:
use an array of const pointers to refer to the individual structures, and export
this pointer array through the linker script rather than the structures per se.
It will consume 32 extra bytes per tracepoint (24 for structure padding and 8
for the pointers), but are less likely to break due to compiler changes.

History:

commit 7e066fb8 tracepoints: add DECLARE_TRACE() and DEFINE_TRACE()
added the aligned(32) type and variable attribute to the tracepoint structures
to deal with gcc happily aligning statically defined structures on 32-byte
multiples.

One attempt was to use a 8-byte alignment for tracepoint structures by applying
both the variable and type attribute to tracepoint structures definitions and
declarations. It worked fine with gcc 4.5.1, but broke with gcc 4.4.4 and 4.4.5.

The reason is that the "aligned" attribute only specify the _minimum_ alignment
for a structure, leaving both the compiler and the linker free to align on
larger multiples. Because tracepoint.c expects the structures to be placed as an
array within each section, up-alignment cause NULL-pointer exceptions due to the
extra unexpected padding.

(this patch applies on top of -tip)

Signed-off-by: Mathieu Desnoyers 
Acked-by: David S. Miller 
LKML-Reference: <20110126222622.GA10794@Krystal>
CC: Frederic Weisbecker 
CC: Ingo Molnar 
CC: Thomas Gleixner 
CC: Andrew Morton 
CC: Peter Zijlstra 
CC: Rusty Russell 
Signed-off-by: Steven Rostedt

jump_label: Use more consistent naming

2010-10-18T17:58:56+00:00

Now that there's still only a few users around, rename things to make
them more consistent.

Signed-off-by: Peter Zijlstra 
LKML-Reference: <20101014203625.448565169@chello.nl>
Signed-off-by: Ingo Molnar

jump label: Tracepoint support for jump labels

2010-09-22T20:31:01+00:00

Make use of the jump label infrastructure for tracepoints.

Signed-off-by: Jason Baron 
LKML-Reference: 
Signed-off-by: Steven Rostedt

tracing: Let tracepoints have data passed to tracepoint callbacks

2010-05-14T13:50:34+00:00

This patch adds data to be passed to tracepoint callbacks.

The created functions from DECLARE_TRACE() now need a mandatory data
parameter. For example:

DECLARE_TRACE(mytracepoint, int value, value)

Will create the register function:

int register_trace_mytracepoint((void(*)(void *data, int value))probe,
                                void *data);

As the first argument, all callbacks (probes) must take a (void *data)
parameter. So a callback for the above tracepoint will look like:

void myprobe(void *data, int value)
{
}

The callback may choose to ignore the data parameter.

This change allows callbacks to register a private data pointer along
with the function probe.

	void mycallback(void *data, int value);

	register_trace_mytracepoint(mycallback, mydata);

Then the mycallback() will receive the "mydata" as the first parameter
before the args.

A more detailed example:

  DECLARE_TRACE(mytracepoint, TP_PROTO(int status), TP_ARGS(status));

  /* In the C file */

  DEFINE_TRACE(mytracepoint, TP_PROTO(int status), TP_ARGS(status));

  [...]

       trace_mytracepoint(status);

  /* In a file registering this tracepoint */

  int my_callback(void *data, int status)
  {
	struct my_struct my_data = data;
	[...]
  }

  [...]
	my_data = kmalloc(sizeof(*my_data), GFP_KERNEL);
	init_my_data(my_data);
	register_trace_mytracepoint(my_callback, my_data);

The same callback can also be registered to the same tracepoint as long
as the data registered is different. Note, the data must also be used
to unregister the callback:

	unregister_trace_mytracepoint(my_callback, my_data);

Because of the data parameter, tracepoints declared this way can not have
no args. That is:

  DECLARE_TRACE(mytracepoint, TP_PROTO(void), TP_ARGS());

will cause an error.

If no arguments are needed, a new macro can be used instead:

  DECLARE_TRACE_NOARGS(mytracepoint);

Since there are no arguments, the proto and args fields are left out.

This is part of a series to make the tracepoint footprint smaller:

   text	   data	    bss	    dec	    hex	filename
4913961	1088356	 861512	6863829	 68bbd5	vmlinux.orig
4914025	1088868	 861512	6864405	 68be15	vmlinux.class
4918492	1084612	 861512	6864616	 68bee8	vmlinux.tracepoint

Again, this patch also increases the size of the kernel, but
lays the ground work for decreasing it.

 v5: Fixed net/core/drop_monitor.c to handle these updates.

 v4: Moved the DECLARE_TRACE() DECLARE_TRACE_NOARGS out of the
     #ifdef CONFIG_TRACE_POINTS, since the two are the same in both
     cases. The __DECLARE_TRACE() is what changes.
     Thanks to Frederic Weisbecker for pointing this out.

 v3: Made all register_* functions require data to be passed and
     all callbacks to take a void * parameter as its first argument.
     This makes the calling functions comply with C standards.

     Also added more comments to the modifications of DECLARE_TRACE().

 v2: Made the DECLARE_TRACE() have the ability to pass arguments
     and added a new DECLARE_TRACE_NOARGS() for tracepoints that
     do not need any arguments.

Acked-by: Mathieu Desnoyers 
Acked-by: Masami Hiramatsu 
Acked-by: Frederic Weisbecker 
Cc: Neil Horman 
Cc: David S. Miller 
Signed-off-by: Steven Rostedt

trivial: fix typo "to to" in multiple files

2009-09-21T13:14:55+00:00

Signed-off-by: Anand Gadiyar 
Signed-off-by: Jiri Kosina

tracing: Don't trace kernel thread syscalls

2009-08-26T19:29:52+00:00

Kernel threads don't call syscalls using the sysenter/sysexit
path. Instead they directly call the sys_* or do_* functions
that implement the syscalls inside the kernel.

The current syscall tracepoints only bind the sysenter/sysexit
path, then it has no effect to trace the kernel thread calls
to syscalls in that path.
Setting the TIF_SYSCALL_TRACEPOINT flag is then useless for these.

Actually there is only one case when a kernel thread can reach the
usual syscall exit tracing path: when we create a kernel thread, the
child comes to ret_from_fork and is the fork() return is then traced.
But this information alone is useless, then we don't want to set the
TIF flags for these threads.

Kernel threads have task_struct->mm set to NULL.
(Thanks to Heiko for that hint ;-)
The idea is then to check the mm field in syscall_regfunc() and
set the flag accordingly.

Signed-off-by: Hendrik Brueckner 
Cc: Jason Baron 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Lai Jiangshan 
Cc: Steven Rostedt 
Cc: Peter Zijlstra 
Cc: Mathieu Desnoyers 
Cc: Jiaying Zhang 
Cc: Martin Bligh 
Cc: Li Zefan 
Cc: Martin Schwidefsky 
Cc: Paul Mundt 
Cc: Heiko Carstens 
Cc: Hendrik Brueckner 
LKML-Reference: <20090825160237.GG4639@cetus.boeblingen.de.ibm.com>
Signed-off-by: Frederic Weisbecker

tracing: Move tracepoint callbacks from declaration to definition

2009-08-25T22:36:41+00:00

It's not strictly correct for the tracepoint reg/unreg callbacks to
occur when a client is hooking up, because the actual tracepoint may not
be present yet.  This happens to be fine for syscall, since that's in
the core kernel, but it would cause problems for tracepoints defined in
a module that hasn't been loaded yet.  It also means the reg/unreg has
to be EXPORTed for any modules to use the tracepoint (as in SystemTap).

This patch removes DECLARE_TRACE_WITH_CALLBACK, and instead introduces
DEFINE_TRACE_FN which stores the callbacks in struct tracepoint.  The
callbacks are used now when the active state of the tracepoint changes
in set_tracepoint & disable_tracepoint.

This also introduces TRACE_EVENT_FN, so ftrace events can also provide
registration callbacks if needed.

Signed-off-by: Josh Stone 
Cc: Jason Baron 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Li Zefan 
Cc: Steven Rostedt 
Cc: Peter Zijlstra 
Cc: Mathieu Desnoyers 
Cc: Jiaying Zhang 
Cc: Martin Bligh 
Cc: Lai Jiangshan 
Cc: Paul Mundt 
Cc: Martin Schwidefsky 
Cc: Heiko Carstens 
LKML-Reference: <1251150194-1713-4-git-send-email-jistone@redhat.com>
Signed-off-by: Frederic Weisbecker

tracing: Make syscall tracepoints conditional

2009-08-25T22:24:19+00:00

The syscall enter/exit tracepoints are only supported on archs that
HAVE_SYSCALL_TRACEPOINTS, so the declarations should be #ifdef'ed.
Also, the definition of syscall_regfunc and syscall_unregfunc should
depend on this same config, rather than the ftrace-specific one.

Signed-off-by: Josh Stone 
Cc: Jason Baron 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Li Zefan 
Cc: Steven Rostedt 
Cc: Peter Zijlstra 
Cc: Mathieu Desnoyers 
Cc: Jiaying Zhang 
Cc: Martin Bligh 
Cc: Lai Jiangshan 
LKML-Reference: <1251150194-1713-3-git-send-email-jistone@redhat.com>
Signed-off-by: Frederic Weisbecker

tracing: Rename FTRACE_SYSCALLS for tracepoints

2009-08-25T22:17:35+00:00

s/HAVE_FTRACE_SYSCALLS/HAVE_SYSCALL_TRACEPOINTS/g
s/TIF_SYSCALL_FTRACE/TIF_SYSCALL_TRACEPOINT/g

The syscall enter/exit tracing is no longer specific to just ftrace, so
they now have names that reflect their tie to tracepoints instead.

Signed-off-by: Josh Stone 
Cc: Jason Baron 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Li Zefan 
Cc: Steven Rostedt 
Cc: Peter Zijlstra 
Cc: Mathieu Desnoyers 
Cc: Jiaying Zhang 
Cc: Martin Bligh 
Cc: Lai Jiangshan 
Cc: Paul Mundt 
Cc: Martin Schwidefsky 
Cc: Heiko Carstens 
LKML-Reference: <1251150194-1713-2-git-send-email-jistone@redhat.com>
Signed-off-by: Frederic Weisbecker

tracing: Eliminate code duplication in kernel/tracepoint.c

2009-08-25T14:15:12+00:00

Signed-off-by: Anirban Sinha 
Reviewed-by: Li Zefan 
Cc: "Oleg Nesterov" 
LKML-Reference: 
Signed-off-by: Ingo Molnar