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Commit 03b30d15 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

Merge branch 'tracing/ftrace' into tracing/core

parents b43f7093 3690b5e6

Documentation/ftrace.txt

+74 −0
Original line number Diff line number Diff line
@@ -165,6 +165,8 @@ Here is the list of current tracers that may be configured. 
  nop - This is not a tracer. To remove all tracers from tracing

		simply echo "nop" into current_tracer.



  hw-branch-tracer - traces branches on all cpu's in a circular buffer.





Examples of using the tracer

----------------------------
@@ -1152,6 +1154,78 @@ int main (int argc, char **argv) 
        return 0;

}





hw-branch-tracer (x86 only)

---------------------------



This tracer uses the x86 last branch tracing hardware feature to

collect a branch trace on all cpus with relatively low overhead.



The tracer uses a fixed-size circular buffer per cpu and only

traces ring 0 branches. The trace file dumps that buffer in the

following format:



# tracer: hw-branch-tracer

#

# CPU#        TO  <-  FROM

   0  scheduler_tick+0xb5/0x1bf	  <-  task_tick_idle+0x5/0x6

   2  run_posix_cpu_timers+0x2b/0x72a	  <-  run_posix_cpu_timers+0x25/0x72a

   0  scheduler_tick+0x139/0x1bf	  <-  scheduler_tick+0xed/0x1bf

   0  scheduler_tick+0x17c/0x1bf	  <-  scheduler_tick+0x148/0x1bf

   2  run_posix_cpu_timers+0x9e/0x72a	  <-  run_posix_cpu_timers+0x5e/0x72a

   0  scheduler_tick+0x1b6/0x1bf	  <-  scheduler_tick+0x1aa/0x1bf





The tracer may be used to dump the trace for the oops'ing cpu on a

kernel oops into the system log. To enable this, ftrace_dump_on_oops

must be set. To set ftrace_dump_on_oops, one can either use the sysctl

function or set it via the proc system interface.



  sysctl kernel.ftrace_dump_on_oops=1



or



  echo 1 > /proc/sys/kernel/ftrace_dump_on_oops





Here's an example of such a dump after a null pointer dereference in a

kernel module:



[57848.105921] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000

[57848.106019] IP: [<ffffffffa0000006>] open+0x6/0x14 [oops]

[57848.106019] PGD 2354e9067 PUD 2375e7067 PMD 0

[57848.106019] Oops: 0002 [#1] SMP

[57848.106019] last sysfs file: /sys/devices/pci0000:00/0000:00:1e.0/0000:20:05.0/local_cpus

[57848.106019] Dumping ftrace buffer:

[57848.106019] ---------------------------------

[...]

[57848.106019]    0  chrdev_open+0xe6/0x165	  <-  cdev_put+0x23/0x24

[57848.106019]    0  chrdev_open+0x117/0x165	  <-  chrdev_open+0xfa/0x165

[57848.106019]    0  chrdev_open+0x120/0x165	  <-  chrdev_open+0x11c/0x165

[57848.106019]    0  chrdev_open+0x134/0x165	  <-  chrdev_open+0x12b/0x165

[57848.106019]    0  open+0x0/0x14 [oops]	  <-  chrdev_open+0x144/0x165

[57848.106019]    0  page_fault+0x0/0x30	  <-  open+0x6/0x14 [oops]

[57848.106019]    0  error_entry+0x0/0x5b	  <-  page_fault+0x4/0x30

[57848.106019]    0  error_kernelspace+0x0/0x31	  <-  error_entry+0x59/0x5b

[57848.106019]    0  error_sti+0x0/0x1	  <-  error_kernelspace+0x2d/0x31

[57848.106019]    0  page_fault+0x9/0x30	  <-  error_sti+0x0/0x1

[57848.106019]    0  do_page_fault+0x0/0x881	  <-  page_fault+0x1a/0x30

[...]

[57848.106019]    0  do_page_fault+0x66b/0x881	  <-  is_prefetch+0x1ee/0x1f2

[57848.106019]    0  do_page_fault+0x6e0/0x881	  <-  do_page_fault+0x67a/0x881

[57848.106019]    0  oops_begin+0x0/0x96	  <-  do_page_fault+0x6e0/0x881

[57848.106019]    0  trace_hw_branch_oops+0x0/0x2d	  <-  oops_begin+0x9/0x96

[...]

[57848.106019]    0  ds_suspend_bts+0x2a/0xe3	  <-  ds_suspend_bts+0x1a/0xe3

[57848.106019] ---------------------------------

[57848.106019] CPU 0

[57848.106019] Modules linked in: oops

[57848.106019] Pid: 5542, comm: cat Tainted: G        W  2.6.28 #23

[57848.106019] RIP: 0010:[<ffffffffa0000006>]  [<ffffffffa0000006>] open+0x6/0x14 [oops]

[57848.106019] RSP: 0018:ffff880235457d48  EFLAGS: 00010246

[...]





dynamic ftrace

--------------

arch/x86/kernel/ds.c

+17 −14
Original line number Diff line number Diff line
@@ -15,8 +15,8 @@ 
 * - buffer allocation (memory accounting)

 *

 *

 * Copyright (C) 2007-2008 Intel Corporation.

 * Markus Metzger <markus.t.metzger@intel.com>, 2007-2008

 * Copyright (C) 2007-2009 Intel Corporation.

 * Markus Metzger <markus.t.metzger@intel.com>, 2007-2009

 */
@@ -890,7 +890,7 @@ int ds_set_pebs_reset(struct pebs_tracer *tracer, u64 value) 
}



static const struct ds_configuration ds_cfg_netburst = {

	.name = "netburst",

	.name = "Netburst",

	.ctl[dsf_bts]		= (1 << 2) | (1 << 3),

	.ctl[dsf_bts_kernel]	= (1 << 5),

	.ctl[dsf_bts_user]	= (1 << 6),
@@ -904,7 +904,7 @@ static const struct ds_configuration ds_cfg_netburst = { 
#endif

};

static const struct ds_configuration ds_cfg_pentium_m = {

	.name = "pentium m",

	.name = "Pentium M",

	.ctl[dsf_bts]		= (1 << 6) | (1 << 7),



	.sizeof_field		= sizeof(long),
@@ -915,8 +915,8 @@ static const struct ds_configuration ds_cfg_pentium_m = { 
	.sizeof_rec[ds_pebs]	= sizeof(long) * 18,

#endif

};

static const struct ds_configuration ds_cfg_core2 = {

	.name = "core 2",

static const struct ds_configuration ds_cfg_core2_atom = {

	.name = "Core 2/Atom",

	.ctl[dsf_bts]		= (1 << 6) | (1 << 7),

	.ctl[dsf_bts_kernel]	= (1 << 9),

	.ctl[dsf_bts_user]	= (1 << 10),
@@ -949,19 +949,22 @@ void __cpuinit ds_init_intel(struct cpuinfo_x86 *c) 
	switch (c->x86) {

	case 0x6:

		switch (c->x86_model) {

		case 0 ... 0xC:

			/* sorry, don't know about them */

			break;

		case 0xD:

		case 0xE: /* Pentium M */

		case 0x9:

		case 0xd: /* Pentium M */

			ds_configure(&ds_cfg_pentium_m);

			break;

		default: /* Core2, Atom, ... */

			ds_configure(&ds_cfg_core2);

		case 0xf:

		case 0x17: /* Core2 */

		case 0x1c: /* Atom */

			ds_configure(&ds_cfg_core2_atom);

			break;

		case 0x1a: /* i7 */

		default:

			/* sorry, don't know about them */

			break;

		}

		break;

	case 0xF:

	case 0xf:

		switch (c->x86_model) {

		case 0x0:

		case 0x1:

arch/x86/kernel/dumpstack.c

+6 −0
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/bug.h>

#include <linux/nmi.h>

#include <linux/sysfs.h>

#include <linux/ftrace.h>



#include <asm/stacktrace.h>
@@ -195,6 +196,11 @@ unsigned __kprobes long oops_begin(void) 
	int cpu;

	unsigned long flags;



	/* notify the hw-branch tracer so it may disable tracing and

	   add the last trace to the trace buffer -

	   the earlier this happens, the more useful the trace. */

	trace_hw_branch_oops();



	oops_enter();



	/* racy, but better than risking deadlock. */

include/linux/ftrace.h

+13 −0
Original line number Diff line number Diff line
@@ -496,4 +496,17 @@ static inline int test_tsk_trace_graph(struct task_struct *tsk) 


#endif /* CONFIG_TRACING */





#ifdef CONFIG_HW_BRANCH_TRACER



void trace_hw_branch(u64 from, u64 to);

void trace_hw_branch_oops(void);



#else /* CONFIG_HW_BRANCH_TRACER */



static inline void trace_hw_branch(u64 from, u64 to) {}

static inline void trace_hw_branch_oops(void) {}



#endif /* CONFIG_HW_BRANCH_TRACER */



#endif /* _LINUX_FTRACE_H */

kernel/trace/trace.h

+0 −1
Original line number Diff line number Diff line
@@ -438,7 +438,6 @@ void trace_function(struct trace_array *tr, 


void trace_graph_return(struct ftrace_graph_ret *trace);

int trace_graph_entry(struct ftrace_graph_ent *trace);

void trace_hw_branch(struct trace_array *tr, u64 from, u64 to);



void tracing_start_cmdline_record(void);

void tracing_stop_cmdline_record(void);