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[PATCH] jump_label: invoke jump_label_test() via early_initcall()

Fengguang Wu reported that running the rcuperf test during boot can cause
the jump_label_test() to hit a WARN_ON(). The issue is that the core jump
label code relies on kernel_text_address() to detect when it can no longer
update branches that may be contained in __init sections. The
kernel_text_address() in turn assumes that if the system_state variable is
greter than or equal to SYSTEM_RUNNING then __init sections are no longer
valid (since the assumption is that they have been freed). However, when
rcuperf is setup to run in early boot it can call kernel_power_off() which
sets the system_state to SYSTEM_POWER_OFF.

Since rcuperf initialization is invoked via a module_init(), we can make
the dependency of jump_label_test() needing to complete before rcuperf
explicit by calling it via early_initcall().

Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Jason Baron <jbaron@xxxxxxxxxx>
 kernel/jump_label.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 0bf2e8f5..7c3774a 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -769,7 +769,7 @@ static __init int jump_label_test(void)
 	return 0;
 #endif /* HAVE_JUMP_LABEL */