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x86, bts, hw-branch-tracer: add _noirq variants to the debug store interface

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The hw-branch-tracer uses debug store functions from an on_each_cpu()
context, which is simply wrong since the functions may sleep.

Add _noirq variants for most functions, which  may be called with
interrupts disabled.

Separate per-cpu and per-task tracing and allow per-cpu tracing to be
controlled from any cpu.

Make the hw-branch-tracer use the new debug store interface, synchronize
with hotplug cpu event using get/put_online_cpus(), and remove the
unnecessary spinlock.

Make the ptrace bts and the ds selftest code use the new interface.

Defer the ds selftest.

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Cc: roland@redhat.com
Cc: eranian@googlemail.com
Cc: oleg@redhat.com
Cc: juan.villacis@intel.com
Cc: ak@linux.jf.intel.com
LKML-Reference: <20090403144555.658136000@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Markus Metzger
2009-04-03 16:43:40 +02:00
committed by Ingo Molnar
parent 35bb7600c1
commit de79f54f53
5 changed files with 492 additions and 246 deletions
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191
kernel/trace/trace_hw_branches.c
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@@ -4,7 +4,6 @@
* Copyright (C) 2008-2009 Intel Corporation.
* Markus Metzger <markus.t.metzger@gmail.com>, 2008-2009
*/
#include <linux/spinlock.h>
#include <linux/kallsyms.h>
#include <linux/debugfs.h>
#include <linux/ftrace.h>
@@ -21,168 +20,113 @@
#define BTS_BUFFER_SIZE (1 << 13)
/*
* The tracer lock protects the below per-cpu tracer array.
* It needs to be held to:
* - start tracing on all cpus
* - stop tracing on all cpus
* - start tracing on a single hotplug cpu
* - stop tracing on a single hotplug cpu
* - read the trace from all cpus
* - read the trace from a single cpu
*/
static DEFINE_SPINLOCK(bts_tracer_lock);
static DEFINE_PER_CPU(struct bts_tracer *, tracer);
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 trace_hw_branches_enabled __read_mostly;
static int trace_hw_branches_suspended __read_mostly;
static struct trace_array *hw_branch_trace __read_mostly;
/*
* Initialize the tracer for the current cpu.
* The argument is ignored.
*
* pre: bts_tracer_lock must be locked.
*/
static void bts_trace_init_cpu(void *arg)
static void bts_trace_init_cpu(int cpu)
{
if (this_tracer)
ds_release_bts(this_tracer);
per_cpu(tracer, cpu) =
ds_request_bts_cpu(cpu, per_cpu(buffer, cpu), BTS_BUFFER_SIZE,
NULL, (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;
}
if (IS_ERR(per_cpu(tracer, cpu)))
per_cpu(tracer, cpu) = NULL;
}
static int bts_trace_init(struct trace_array *tr)
{
int cpu, avail;
spin_lock(&bts_tracer_lock);
int cpu;
hw_branch_trace = tr;
trace_hw_branches_enabled = 0;
on_each_cpu(bts_trace_init_cpu, NULL, 1);
get_online_cpus();
for_each_online_cpu(cpu) {
bts_trace_init_cpu(cpu);
/* 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);
if (likely(per_cpu(tracer, cpu)))
trace_hw_branches_enabled = 1;
}
trace_hw_branches_suspended = 0;
spin_unlock(&bts_tracer_lock);
put_online_cpus();
/* If we could not enable tracing on a single cpu, we fail. */
return avail ? 0 : -EOPNOTSUPP;
}
/*
* Release the tracer for the current cpu.
* The argument is ignored.
*
* pre: bts_tracer_lock must be locked.
*/
static void bts_trace_release_cpu(void *arg)
{
if (this_tracer) {
ds_release_bts(this_tracer);
this_tracer = NULL;
}
return trace_hw_branches_enabled ? 0 : -EOPNOTSUPP;
}
static void bts_trace_reset(struct trace_array *tr)
{
spin_lock(&bts_tracer_lock);
int cpu;
on_each_cpu(bts_trace_release_cpu, NULL, 1);
get_online_cpus();
for_each_online_cpu(cpu) {
if (likely(per_cpu(tracer, cpu))) {
ds_release_bts(per_cpu(tracer, cpu));
per_cpu(tracer, cpu) = NULL;
}
}
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);
put_online_cpus();
}
static void bts_trace_start(struct trace_array *tr)
{
spin_lock(&bts_tracer_lock);
int cpu;
on_each_cpu(bts_trace_resume_cpu, NULL, 1);
get_online_cpus();
for_each_online_cpu(cpu)
if (likely(per_cpu(tracer, cpu)))
ds_resume_bts(per_cpu(tracer, cpu));
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);
put_online_cpus();
}
static void bts_trace_stop(struct trace_array *tr)
{
spin_lock(&bts_tracer_lock);
int cpu;
on_each_cpu(bts_trace_suspend_cpu, NULL, 1);
get_online_cpus();
for_each_online_cpu(cpu)
if (likely(per_cpu(tracer, cpu)))
ds_suspend_bts(per_cpu(tracer, cpu));
trace_hw_branches_suspended = 1;
spin_unlock(&bts_tracer_lock);
put_online_cpus();
}
static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
spin_lock(&bts_tracer_lock);
if (!trace_hw_branches_enabled)
goto out;
int cpu = (long)hcpu;
switch (action) {
case CPU_ONLINE:
case CPU_DOWN_FAILED:
smp_call_function_single(cpu, bts_trace_init_cpu, NULL, 1);
/* The notification is sent with interrupts enabled. */
if (trace_hw_branches_enabled) {
bts_trace_init_cpu(cpu);
if (trace_hw_branches_suspended)
smp_call_function_single(cpu, bts_trace_suspend_cpu,
NULL, 1);
if (trace_hw_branches_suspended &&
likely(per_cpu(tracer, cpu)))
ds_suspend_bts(per_cpu(tracer, cpu));
}
break;
case CPU_DOWN_PREPARE:
smp_call_function_single(cpu, bts_trace_release_cpu, NULL, 1);
break;
/* The notification is sent with interrupts enabled. */
if (likely(per_cpu(tracer, cpu))) {
ds_release_bts(per_cpu(tracer, cpu));
per_cpu(tracer, cpu) = NULL;
}
}
out:
spin_unlock(&bts_tracer_lock);
return NOTIFY_DONE;
}
@@ -274,7 +218,7 @@ static void trace_bts_at(const struct bts_trace *trace, void *at)
/*
* Collect the trace on the current cpu and write it into the ftrace buffer.
*
* pre: bts_tracer_lock must be locked
* pre: tracing must be suspended on the current cpu
*/
static void trace_bts_cpu(void *arg)
{
@@ -291,10 +235,9 @@ static void trace_bts_cpu(void *arg)
if (unlikely(!this_tracer))
return;
ds_suspend_bts(this_tracer);
trace = ds_read_bts(this_tracer);
if (!trace)
goto out;
return;
for (at = trace->ds.top; (void *)at < trace->ds.end;
at += trace->ds.size)
@@ -303,18 +246,27 @@ static void trace_bts_cpu(void *arg)
for (at = trace->ds.begin; (void *)at < trace->ds.top;
at += trace->ds.size)
trace_bts_at(trace, at);
out:
ds_resume_bts(this_tracer);
}
static void trace_bts_prepare(struct trace_iterator *iter)
{
spin_lock(&bts_tracer_lock);
int cpu;
get_online_cpus();
for_each_online_cpu(cpu)
if (likely(per_cpu(tracer, cpu)))
ds_suspend_bts(per_cpu(tracer, cpu));
/*
* We need to collect the trace on the respective cpu since ftrace
* implicitly adds the record for the current cpu.
* Once that is more flexible, we could collect the data from any cpu.
*/
on_each_cpu(trace_bts_cpu, iter->tr, 1);
spin_unlock(&bts_tracer_lock);
for_each_online_cpu(cpu)
if (likely(per_cpu(tracer, cpu)))
ds_resume_bts(per_cpu(tracer, cpu));
put_online_cpus();
}
static void trace_bts_close(struct trace_iterator *iter)
@@ -324,12 +276,11 @@ static void trace_bts_close(struct trace_iterator *iter)
void trace_hw_branch_oops(void)
{
spin_lock(&bts_tracer_lock);
if (trace_hw_branches_enabled)
if (this_tracer) {
ds_suspend_bts_noirq(this_tracer);
trace_bts_cpu(hw_branch_trace);
spin_unlock(&bts_tracer_lock);
ds_resume_bts_noirq(this_tracer);
}
}
struct tracer bts_tracer __read_mostly =