[PATCH] perf_counter: more barrier in blank weak function

[Yinghai Lu]

Impact: fix panic possible panic

Some versions of GCC inline the weak global function if it's empty.
Add a barrier() to work it around.

Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
 kernel/perf_counter.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index d7a79f3..37f7716 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -45,8 +45,8 @@ hw_perf_counter_init(struct perf_counter *counter)
 }
 
 u64 __weak hw_perf_save_disable(void)		{ return 0; }
-void __weak hw_perf_restore(u64 ctrl)		{ }
-void __weak hw_perf_counter_setup(void)		{ }
+void __weak hw_perf_restore(u64 ctrl)		{ barrier(); }
+void __weak hw_perf_counter_setup(void)		{ barrier(); }
 
 static void
 list_add_counter(struct perf_counter *counter, struct perf_counter_context *ctx)
--
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