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Commit ba9372a8 authored by Markus Metzger's avatar Markus Metzger Committed by Ingo Molnar
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x86, hw-branch-tracer: keep resources on stop 



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: default avatarMarkus Metzger <markus.t.metzger@intel.com>
LKML-Reference: <20090313104852.A30168@sedona.ch.intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent b8e47195

kernel/trace/trace_hw_branches.c

+85 −34
Original line number Diff line number Diff line
@@ -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_stop(struct trace_array *tr)

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;

	on_each_cpu(bts_trace_stop_cpu, NULL, 1);

	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);



	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");
@@ -276,6 +326,7 @@ void trace_hw_branch_oops(void) 
{

	spin_lock(&bts_tracer_lock);



	if (trace_hw_branches_enabled)

		trace_bts_cpu(hw_branch_trace);



	spin_unlock(&bts_tracer_lock);