x86, ftrace, hw-branch-tracer: support hotplug cpus

Support hotplug cpus.

Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Markus Metzger 2009-01-19 10:26:53 +01:00 committed by Ingo Molnar
parent b43f70933e
commit 5c5317de14

View file

@ -1,7 +1,8 @@
/*
* h/w branch tracer for x86 based on bts
*
* Copyright (C) 2008 Markus Metzger <markus.t.metzger@gmail.com>
* Copyright (C) 2008-2009 Intel Corporation.
* Markus Metzger <markus.t.metzger@gmail.com>, 2008-2009
*
*/
@ -10,6 +11,9 @@
#include <linux/debugfs.h>
#include <linux/ftrace.h>
#include <linux/kallsyms.h>
#include <linux/mutex.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <asm/ds.h>
@ -19,13 +23,31 @@
#define SIZEOF_BTS (1 << 13)
/* The tracer mutex 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_MUTEX(bts_tracer_mutex);
static DEFINE_PER_CPU(struct bts_tracer *, tracer);
static DEFINE_PER_CPU(unsigned char[SIZEOF_BTS], 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;
/*
* Start tracing on the current cpu.
* The argument is ignored.
*
* pre: bts_tracer_mutex must be locked.
*/
static void bts_trace_start_cpu(void *arg)
{
if (this_tracer)
@ -43,14 +65,20 @@ static void bts_trace_start_cpu(void *arg)
static void bts_trace_start(struct trace_array *tr)
{
int cpu;
mutex_lock(&bts_tracer_mutex);
tracing_reset_online_cpus(tr);
on_each_cpu(bts_trace_start_cpu, NULL, 1);
trace_hw_branches_enabled = 1;
for_each_cpu(cpu, cpu_possible_mask)
smp_call_function_single(cpu, bts_trace_start_cpu, NULL, 1);
mutex_unlock(&bts_tracer_mutex);
}
/*
* Start tracing on the current cpu.
* The argument is ignored.
*
* pre: bts_tracer_mutex must be locked.
*/
static void bts_trace_stop_cpu(void *arg)
{
if (this_tracer) {
@ -61,20 +89,58 @@ static void bts_trace_stop_cpu(void *arg)
static void bts_trace_stop(struct trace_array *tr)
{
int cpu;
mutex_lock(&bts_tracer_mutex);
for_each_cpu(cpu, cpu_possible_mask)
smp_call_function_single(cpu, bts_trace_stop_cpu, NULL, 1);
trace_hw_branches_enabled = 0;
on_each_cpu(bts_trace_stop_cpu, NULL, 1);
mutex_unlock(&bts_tracer_mutex);
}
static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
mutex_lock(&bts_tracer_mutex);
if (!trace_hw_branches_enabled)
goto out;
switch (action) {
case CPU_ONLINE:
case CPU_DOWN_FAILED:
smp_call_function_single(cpu, bts_trace_start_cpu, NULL, 1);
break;
case CPU_DOWN_PREPARE:
smp_call_function_single(cpu, bts_trace_stop_cpu, NULL, 1);
break;
}
out:
mutex_unlock(&bts_tracer_mutex);
return NOTIFY_DONE;
}
static struct notifier_block bts_hotcpu_notifier __cpuinitdata = {
.notifier_call = bts_hotcpu_handler
};
static int bts_trace_init(struct trace_array *tr)
{
register_hotcpu_notifier(&bts_hotcpu_notifier);
tracing_reset_online_cpus(tr);
bts_trace_start(tr);
return 0;
}
static void bts_trace_reset(struct trace_array *tr)
{
bts_trace_stop(tr);
unregister_hotcpu_notifier(&bts_hotcpu_notifier);
}
static void bts_trace_print_header(struct seq_file *m)
{
seq_puts(m,
@ -108,18 +174,34 @@ void trace_hw_branch(struct trace_array *tr, u64 from, u64 to)
{
struct ring_buffer_event *event;
struct hw_branch_entry *entry;
unsigned long irq;
unsigned long irq1, irq2;
int cpu;
event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry), &irq);
if (!event)
if (unlikely(!tr))
return;
if (unlikely(!trace_hw_branches_enabled))
return;
local_irq_save(irq1);
cpu = raw_smp_processor_id();
if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
goto out;
event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry), &irq2);
if (!event)
goto out;
entry = ring_buffer_event_data(event);
tracing_generic_entry_update(&entry->ent, 0, from);
entry->ent.type = TRACE_HW_BRANCHES;
entry->ent.cpu = smp_processor_id();
entry->ent.cpu = cpu;
entry->from = from;
entry->to = to;
ring_buffer_unlock_commit(tr->buffer, event, irq);
ring_buffer_unlock_commit(tr->buffer, event, irq2);
out:
atomic_dec(&tr->data[cpu]->disabled);
local_irq_restore(irq1);
}
static void trace_bts_at(struct trace_array *tr,
@ -143,6 +225,11 @@ static void trace_bts_at(struct trace_array *tr,
}
}
/*
* Collect the trace on the current cpu and write it into the ftrace buffer.
*
* pre: bts_tracer_mutex must be locked
*/
static void trace_bts_cpu(void *arg)
{
struct trace_array *tr = (struct trace_array *) arg;
@ -152,6 +239,9 @@ static void trace_bts_cpu(void *arg)
if (!this_tracer)
return;
if (unlikely(atomic_read(&tr->data[raw_smp_processor_id()]->disabled)))
return;
ds_suspend_bts(this_tracer);
trace = ds_read_bts(this_tracer);
if (!trace)
@ -171,17 +261,18 @@ out:
static void trace_bts_prepare(struct trace_iterator *iter)
{
int cpu;
mutex_lock(&bts_tracer_mutex);
for_each_cpu(cpu, cpu_possible_mask)
smp_call_function_single(cpu, trace_bts_cpu, iter->tr, 1);
on_each_cpu(trace_bts_cpu, iter->tr, 1);
mutex_unlock(&bts_tracer_mutex);
}
struct tracer bts_tracer __read_mostly =
{
.name = "hw-branch-tracer",
.init = bts_trace_init,
.reset = bts_trace_stop,
.reset = bts_trace_reset,
.print_header = bts_trace_print_header,
.print_line = bts_trace_print_line,
.start = bts_trace_start,