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-rw-r--r--kernel/trace/Kconfig8
-rw-r--r--kernel/trace/ring_buffer.c4
2 files changed, 12 insertions, 0 deletions
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 163fbfc2f39..1ea0d1234f4 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -62,6 +62,12 @@ config EVENT_TRACING
config CONTEXT_SWITCH_TRACER
bool
+config RING_BUFFER_ALLOW_SWAP
+ bool
+ help
+ Allow the use of ring_buffer_swap_cpu.
+ Adds a very slight overhead to tracing when enabled.
+
# All tracer options should select GENERIC_TRACER. For those options that are
# enabled by all tracers (context switch and event tracer) they select TRACING.
# This allows those options to appear when no other tracer is selected. But the
@@ -146,6 +152,7 @@ config IRQSOFF_TRACER
select TRACE_IRQFLAGS
select GENERIC_TRACER
select TRACER_MAX_TRACE
+ select RING_BUFFER_ALLOW_SWAP
help
This option measures the time spent in irqs-off critical
sections, with microsecond accuracy.
@@ -167,6 +174,7 @@ config PREEMPT_TRACER
depends on PREEMPT
select GENERIC_TRACER
select TRACER_MAX_TRACE
+ select RING_BUFFER_ALLOW_SWAP
help
This option measures the time spent in preemption off critical
sections, with microsecond accuracy.
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 1766c0e8db5..454e74e718c 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2084,6 +2084,7 @@ rb_reserve_next_event(struct ring_buffer *buffer,
rb_start_commit(cpu_buffer);
+#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
/*
* Due to the ability to swap a cpu buffer from a buffer
* it is possible it was swapped before we committed.
@@ -2096,6 +2097,7 @@ rb_reserve_next_event(struct ring_buffer *buffer,
local_dec(&cpu_buffer->commits);
return NULL;
}
+#endif
length = rb_calculate_event_length(length);
again:
@@ -3498,6 +3500,7 @@ int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
}
EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
+#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
/**
* ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
* @buffer_a: One buffer to swap with
@@ -3573,6 +3576,7 @@ out:
return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
+#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
/**
* ring_buffer_alloc_read_page - allocate a page to read from buffer