ftrace/fastboot: disable tracers self-tests when boot tracer is selected

The tracing engine resets the ring buffer and the tracers touch it
too during self-tests. These self-tests happen during tracers registering
and work against boot tracing which is logging initcalls.

We have to disable tracing self-tests if the boot-tracer is selected.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 3 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 81a17ef6b942..4feb3c81f94d 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -126,7 +126,9 @@ config BOOT_TRACER
           the timings of the initcalls. Its aim is to be parsed by the
           /scripts/bootgraph.pl tool to produce pretty graphics about
           boot inefficiencies, giving a visual representation of the
-          delays during initcalls.
+          delays during initcalls. Note that tracers self tests can't
+          be enabled if this tracer is selected since only one tracer
+          should touch the tracing buffer at a time.
 
 config STACK_TRACER
         bool "Trace max stack"
@@ -168,8 +170,7 @@ config FTRACE_SELFTEST
 
 config FTRACE_STARTUP_TEST
         bool "Perform a startup test on ftrace"
-        depends on TRACING
-        depends on DEBUG_KERNEL
+        depends on TRACING && DEBUG_KERNEL && !BOOT_TRACER
         select FTRACE_SELFTEST
         help
           This option performs a series of startup tests on ftrace. On bootup