[PATCH] tracing/markers: make markers select tracepoints

[Frederic Weisbecker]

Sometimes it happens that KConfig dependencies are not handled
like in the following scenario:

- config A
   bool

- config B
   bool
   depends on A

-config C
   bool
   select B

If one selects C, then it will select B without checking its dependency to A, if A
hasn't been selected elsewhere, it will result in a build crash.

This is what happens on the following build error:

kernel/built-in.o: In function `marker_update_probe_range':
(.text+0x52f64): undefined reference to `tracepoint_probe_register_noupdate'
kernel/built-in.o: In function `marker_update_probe_range':
(.text+0x52f74): undefined reference to `tracepoint_probe_unregister_noupdate'
kernel/built-in.o: In function `marker_update_probe_range':
(.text+0x52fb9): undefined reference to `tracepoint_probe_unregister_noupdate'
kernel/built-in.o: In function `marker_update_probes':
marker.c:(.text+0x530ba): undefined reference to `tracepoint_probe_update_all'

CONFIG_KVM_TRACE will select CONFIG_MARKER, but the latter depends on CONFIG_TRACEPOINTS
which will not be selected.

A temporary fix is to make CONFIG_MARKER select CONFIG_TRACEPOINTS, though it doesn't
fix the source KConfig dependency handling problem.

Reported-by: Ingo Molnar <mingo@xxxxxxx>
Cc: Roman Zippel <zippel@xxxxxxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
---
 init/Kconfig |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index b6400a5..a93f957 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -975,7 +975,7 @@ config TRACEPOINTS
 
 config MARKERS
 	bool "Activate markers"
-	depends on TRACEPOINTS
+	select TRACEPOINTS
 	help
 	  Place an empty function call at each marker site. Can be
 	  dynamically changed for a probe function.
-- 
1.6.1


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