Commit 5c5317de authored by Markus Metzger's avatar Markus Metzger Committed by Ingo Molnar
Browse files

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



Support hotplug cpus.

Reported-by: default avatarAndi Kleen <ak@linux.intel.com>
Signed-off-by: default avatarMarkus Metzger <markus.t.metzger@intel.com>
Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent b43f7093

kernel/trace/trace_hw_branches.c

+107 −16
Original line number Diff line number Diff line 
/*

 * 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);



	trace_hw_branches_enabled = 0;

	on_each_cpu(bts_trace_stop_cpu, NULL, 1);



	for_each_cpu(cpu, cpu_possible_mask)

	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 @@ static void trace_bts_cpu(void *arg) 


static void trace_bts_prepare(struct trace_iterator *iter)

{

	int cpu;

	mutex_lock(&bts_tracer_mutex);



	on_each_cpu(trace_bts_cpu, iter->tr, 1);



	for_each_cpu(cpu, cpu_possible_mask)

		smp_call_function_single(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,