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Commit 8aabee57 authored by Steven Rostedt's avatar Steven Rostedt
Browse files

ring-buffer: remove unneeded get_online_cpus 



Impact: speed up and remove possible races

The get_online_cpus was added to the ring buffer because the original
design would free the ring buffer on a CPU that was being taken
off line. The final design kept the ring buffer around even when the
CPU was taken off line. This is to allow a user to still read the
information on that ring buffer.

Most of the get_online_cpus are no longer needed since the ring buffer will
not disappear from the use cases.

Reported-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
parent 59222efe

kernel/trace/ring_buffer.c

+14 −76
Original line number Diff line number Diff line
@@ -1561,15 +1561,11 @@ void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu) 
{

	struct ring_buffer_per_cpu *cpu_buffer;



	get_online_cpus();



	if (!cpumask_test_cpu(cpu, buffer->cpumask))

		goto out;

		return;



	cpu_buffer = buffer->buffers[cpu];

	atomic_inc(&cpu_buffer->record_disabled);

 out:

	put_online_cpus();

}

EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
@@ -1585,15 +1581,11 @@ void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu) 
{

	struct ring_buffer_per_cpu *cpu_buffer;



	get_online_cpus();



	if (!cpumask_test_cpu(cpu, buffer->cpumask))

		goto out;

		return;



	cpu_buffer = buffer->buffers[cpu];

	atomic_dec(&cpu_buffer->record_disabled);

 out:

	put_online_cpus();

}

EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
@@ -1605,17 +1597,13 @@ EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu); 
unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)

{

	struct ring_buffer_per_cpu *cpu_buffer;

	unsigned long ret = 0;



	get_online_cpus();

	unsigned long ret;



	if (!cpumask_test_cpu(cpu, buffer->cpumask))

		goto out;

		return 0;



	cpu_buffer = buffer->buffers[cpu];

	ret = cpu_buffer->entries;

 out:

	put_online_cpus();



	return ret;

}
@@ -1629,17 +1617,13 @@ EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu); 
unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)

{

	struct ring_buffer_per_cpu *cpu_buffer;

	unsigned long ret = 0;



	get_online_cpus();

	unsigned long ret;



	if (!cpumask_test_cpu(cpu, buffer->cpumask))

		goto out;

		return 0;



	cpu_buffer = buffer->buffers[cpu];

	ret = cpu_buffer->overrun;

 out:

	put_online_cpus();



	return ret;

}
@@ -1658,16 +1642,12 @@ unsigned long ring_buffer_entries(struct ring_buffer *buffer) 
	unsigned long entries = 0;

	int cpu;



	get_online_cpus();



	/* if you care about this being correct, lock the buffer */

	for_each_buffer_cpu(buffer, cpu) {

		cpu_buffer = buffer->buffers[cpu];

		entries += cpu_buffer->entries;

	}



	put_online_cpus();



	return entries;

}

EXPORT_SYMBOL_GPL(ring_buffer_entries);
@@ -1685,16 +1665,12 @@ unsigned long ring_buffer_overruns(struct ring_buffer *buffer) 
	unsigned long overruns = 0;

	int cpu;



	get_online_cpus();



	/* if you care about this being correct, lock the buffer */

	for_each_buffer_cpu(buffer, cpu) {

		cpu_buffer = buffer->buffers[cpu];

		overruns += cpu_buffer->overrun;

	}



	put_online_cpus();



	return overruns;

}

EXPORT_SYMBOL_GPL(ring_buffer_overruns);
@@ -2093,21 +2069,16 @@ struct ring_buffer_event * 
ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)

{

	struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];

	struct ring_buffer_event *event = NULL;

	struct ring_buffer_event *event;

	unsigned long flags;



	get_online_cpus();



	if (!cpumask_test_cpu(cpu, buffer->cpumask))

		goto out;

		return NULL;



	spin_lock_irqsave(&cpu_buffer->reader_lock, flags);

	event = rb_buffer_peek(buffer, cpu, ts);

	spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);



 out:

	put_online_cpus();



	return event;

}
@@ -2189,17 +2160,15 @@ struct ring_buffer_iter * 
ring_buffer_read_start(struct ring_buffer *buffer, int cpu)

{

	struct ring_buffer_per_cpu *cpu_buffer;

	struct ring_buffer_iter *iter = NULL;

	struct ring_buffer_iter *iter;

	unsigned long flags;



	get_online_cpus();



	if (!cpumask_test_cpu(cpu, buffer->cpumask))

		goto out;

		return NULL;



	iter = kmalloc(sizeof(*iter), GFP_KERNEL);

	if (!iter)

		goto out;

		return NULL;



	cpu_buffer = buffer->buffers[cpu];
@@ -2214,9 +2183,6 @@ ring_buffer_read_start(struct ring_buffer *buffer, int cpu) 
	__raw_spin_unlock(&cpu_buffer->lock);

	spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);



 out:

	put_online_cpus();



	return iter;

}

EXPORT_SYMBOL_GPL(ring_buffer_read_start);
@@ -2309,13 +2275,9 @@ void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu) 
{

	struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];

	unsigned long flags;

	int resched;



	/* Can't use get_online_cpus because this can be in atomic */

	resched = ftrace_preempt_disable();



	if (!cpumask_test_cpu(cpu, buffer->cpumask))

		goto out;

		return;



	spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
@@ -2326,8 +2288,6 @@ void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu) 
	__raw_spin_unlock(&cpu_buffer->lock);



	spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);

 out:

	ftrace_preempt_enable(resched);

}

EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
@@ -2337,16 +2297,10 @@ EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu); 
 */

void ring_buffer_reset(struct ring_buffer *buffer)

{

	int resched;

	int cpu;



	/* Can't use get_online_cpus because this can be in atomic */

	resched = ftrace_preempt_disable();



	for_each_buffer_cpu(buffer, cpu)

		ring_buffer_reset_cpu(buffer, cpu);



	ftrace_preempt_enable(resched);

}

EXPORT_SYMBOL_GPL(ring_buffer_reset);
@@ -2359,8 +2313,6 @@ int ring_buffer_empty(struct ring_buffer *buffer) 
	struct ring_buffer_per_cpu *cpu_buffer;

	int cpu;



	get_online_cpus();



	/* yes this is racy, but if you don't like the race, lock the buffer */

	for_each_buffer_cpu(buffer, cpu) {

		cpu_buffer = buffer->buffers[cpu];
@@ -2368,8 +2320,6 @@ int ring_buffer_empty(struct ring_buffer *buffer) 
			return 0;

	}



	put_online_cpus();



	return 1;

}

EXPORT_SYMBOL_GPL(ring_buffer_empty);
@@ -2382,18 +2332,14 @@ EXPORT_SYMBOL_GPL(ring_buffer_empty); 
int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)

{

	struct ring_buffer_per_cpu *cpu_buffer;

	int ret = 1;



	get_online_cpus();

	int ret;



	if (!cpumask_test_cpu(cpu, buffer->cpumask))

		goto out;

		return 1;



	cpu_buffer = buffer->buffers[cpu];

	ret = rb_per_cpu_empty(cpu_buffer);



 out:

	put_online_cpus();



	return ret;

}
@@ -2416,8 +2362,6 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a, 
	struct ring_buffer_per_cpu *cpu_buffer_b;

	int ret = -EINVAL;



	get_online_cpus();



	if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||

	    !cpumask_test_cpu(cpu, buffer_b->cpumask))

		goto out;
@@ -2466,8 +2410,6 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a, 


	ret = 0;

out:

	put_online_cpus();



	return ret;

}

EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
@@ -2583,8 +2525,6 @@ int ring_buffer_read_page(struct ring_buffer *buffer, 
	u64 save_timestamp;

	int ret = -1;



	get_online_cpus();



	if (!cpumask_test_cpu(cpu, buffer->cpumask))

		goto out;
@@ -2681,8 +2621,6 @@ int ring_buffer_read_page(struct ring_buffer *buffer, 
	spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);



 out:

	put_online_cpus();



	return ret;

}