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x86, hw-branch-tracer: keep resources on stop

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Distinguish init/reset and start/stop:

init/reset will allocate and release bts tracing resources
stop/start will suspend and resume bts tracing

Return an error on init() if no cpu can be traced.

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
LKML-Reference: <20090313104852.A30168@sedona.ch.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Markus Metzger 2009-03-13 10:48:52 +01:00 committed by Ingo Molnar
parent b8e4719545
commit ba9372a8f3
1 changed files with 85 additions and 34 deletions
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119
kernel/trace/trace_hw_branches.c
View file

@ -19,7 +19,7 @@
#include "trace_output.h"
#define SIZEOF_BTS (1 << 13)
#define BTS_BUFFER_SIZE (1 << 13)
/*
* The tracer lock protects the below per-cpu tracer array.
@ -33,53 +33,68 @@
*/
static DEFINE_SPINLOCK(bts_tracer_lock);
static DEFINE_PER_CPU(struct bts_tracer *, tracer);
static DEFINE_PER_CPU(unsigned char[SIZEOF_BTS], buffer);
static DEFINE_PER_CPU(unsigned char[BTS_BUFFER_SIZE], buffer);
#define this_tracer per_cpu(tracer, smp_processor_id())
#define this_buffer per_cpu(buffer, smp_processor_id())
static int __read_mostly trace_hw_branches_enabled;
static int trace_hw_branches_enabled __read_mostly;
static int trace_hw_branches_suspended __read_mostly;
static struct trace_array *hw_branch_trace __read_mostly;
/*
* Start tracing on the current cpu.
* Initialize the tracer for the current cpu.
* The argument is ignored.
*
* pre: bts_tracer_lock must be locked.
*/
static void bts_trace_start_cpu(void *arg)
static void bts_trace_init_cpu(void *arg)
{
if (this_tracer)
ds_release_bts(this_tracer);
this_tracer =
ds_request_bts(/* task = */ NULL, this_buffer, SIZEOF_BTS,
/* ovfl = */ NULL, /* th = */ (size_t)-1,
BTS_KERNEL);
this_tracer = ds_request_bts(NULL, this_buffer, BTS_BUFFER_SIZE,
NULL, (size_t)-1, BTS_KERNEL);
if (IS_ERR(this_tracer)) {
this_tracer = NULL;
return;
}
}
static void bts_trace_start(struct trace_array *tr)
static int bts_trace_init(struct trace_array *tr)
{
int cpu, avail;
spin_lock(&bts_tracer_lock);
on_each_cpu(bts_trace_start_cpu, NULL, 1);
trace_hw_branches_enabled = 1;
hw_branch_trace = tr;
on_each_cpu(bts_trace_init_cpu, NULL, 1);
/* Check on how many cpus we could enable tracing */
avail = 0;
for_each_online_cpu(cpu)
if (per_cpu(tracer, cpu))
avail++;
trace_hw_branches_enabled = (avail ? 1 : 0);
trace_hw_branches_suspended = 0;
spin_unlock(&bts_tracer_lock);
/* If we could not enable tracing on a single cpu, we fail. */
return avail ? 0 : -EOPNOTSUPP;
}
/*
* Stop tracing on the current cpu.
* Release the tracer for the current cpu.
* The argument is ignored.
*
* pre: bts_tracer_lock must be locked.
*/
static void bts_trace_stop_cpu(void *arg)
static void bts_trace_release_cpu(void *arg)
{
if (this_tracer) {
ds_release_bts(this_tracer);
@ -87,12 +102,57 @@ static void bts_trace_stop_cpu(void *arg)
}
}
static void bts_trace_reset(struct trace_array *tr)
{
spin_lock(&bts_tracer_lock);
on_each_cpu(bts_trace_release_cpu, NULL, 1);
trace_hw_branches_enabled = 0;
trace_hw_branches_suspended = 0;
spin_unlock(&bts_tracer_lock);
}
/*
* Resume tracing on the current cpu.
* The argument is ignored.
*
* pre: bts_tracer_lock must be locked.
*/
static void bts_trace_resume_cpu(void *arg)
{
if (this_tracer)
ds_resume_bts(this_tracer);
}
static void bts_trace_start(struct trace_array *tr)
{
spin_lock(&bts_tracer_lock);
on_each_cpu(bts_trace_resume_cpu, NULL, 1);
trace_hw_branches_suspended = 0;
spin_unlock(&bts_tracer_lock);
}
/*
* Suspend tracing on the current cpu.
* The argument is ignored.
*
* pre: bts_tracer_lock must be locked.
*/
static void bts_trace_suspend_cpu(void *arg)
{
if (this_tracer)
ds_suspend_bts(this_tracer);
}
static void bts_trace_stop(struct trace_array *tr)
{
spin_lock(&bts_tracer_lock);
trace_hw_branches_enabled = 0;
on_each_cpu(bts_trace_stop_cpu, NULL, 1);
on_each_cpu(bts_trace_suspend_cpu, NULL, 1);
trace_hw_branches_suspended = 1;
spin_unlock(&bts_tracer_lock);
}
@ -110,10 +170,14 @@ static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
switch (action) {
case CPU_ONLINE:
case CPU_DOWN_FAILED:
smp_call_function_single(cpu, bts_trace_start_cpu, NULL, 1);
smp_call_function_single(cpu, bts_trace_init_cpu, NULL, 1);
if (trace_hw_branches_suspended)
smp_call_function_single(cpu, bts_trace_suspend_cpu,
NULL, 1);
break;
case CPU_DOWN_PREPARE:
smp_call_function_single(cpu, bts_trace_stop_cpu, NULL, 1);
smp_call_function_single(cpu, bts_trace_release_cpu, NULL, 1);
break;
}
@ -126,20 +190,6 @@ static struct notifier_block bts_hotcpu_notifier __cpuinitdata = {
.notifier_call = bts_hotcpu_handler
};
static int bts_trace_init(struct trace_array *tr)
{
hw_branch_trace = tr;
bts_trace_start(tr);
return 0;
}
static void bts_trace_reset(struct trace_array *tr)
{
bts_trace_stop(tr);
}
static void bts_trace_print_header(struct seq_file *m)
{
seq_puts(m, "# CPU# TO <- FROM\n");
@ -228,7 +278,7 @@ static void trace_bts_at(const struct bts_trace *trace, void *at)
*/
static void trace_bts_cpu(void *arg)
{
struct trace_array *tr = (struct trace_array *) arg;
struct trace_array *tr = (struct trace_array *)arg;
const struct bts_trace *trace;
unsigned char *at;
@ -276,7 +326,8 @@ void trace_hw_branch_oops(void)
{
spin_lock(&bts_tracer_lock);
trace_bts_cpu(hw_branch_trace);
if (trace_hw_branches_enabled)
trace_bts_cpu(hw_branch_trace);
spin_unlock(&bts_tracer_lock);
}