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: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 2e99dba..969f7cb 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2756,12 +2756,17 @@
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 @@
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;
}