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Commit d4788207 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
Browse files

ring-buffer: add locks around rb_per_cpu_empty 



The checking of whether the buffer is empty or not needs to be serialized
among the readers. Add the reader spin lock around it.

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 5f78abee

kernel/trace/ring_buffer.c

+9 −2
Original line number Diff line number Diff line
@@ -2756,12 +2756,17 @@ EXPORT_SYMBOL_GPL(ring_buffer_reset); 
int ring_buffer_empty(struct ring_buffer *buffer)

{

	struct ring_buffer_per_cpu *cpu_buffer;

	unsigned long flags;

	int cpu;

	int ret;



	/* 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];

		if (!rb_per_cpu_empty(cpu_buffer))

		spin_lock_irqsave(&cpu_buffer->reader_lock, flags);

		ret = rb_per_cpu_empty(cpu_buffer);

		spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);

		if (!ret)

			return 0;

	}
@@ -2777,14 +2782,16 @@ EXPORT_SYMBOL_GPL(ring_buffer_empty); 
int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)

{

	struct ring_buffer_per_cpu *cpu_buffer;

	unsigned long flags;

	int ret;



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

		return 1;



	cpu_buffer = buffer->buffers[cpu];

	spin_lock_irqsave(&cpu_buffer->reader_lock, flags);

	ret = rb_per_cpu_empty(cpu_buffer);



	spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);



	return ret;

}