linux-kernel - [PATCH] jump_label: invoke jump_label_test() via early

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Date:   Mon, 13 Nov 2017 16:48:47 -0500
From:   Jason Baron <jbaron@...mai.com>
To:     rostedt@...dmis.org, peterz@...radead.org
Cc:     linux-kernel@...r.kernel.org,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Ingo Molnar <mingo@...nel.org>
Subject: [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greter than or equal to SYSTEM_RUNNING then __init sections are no longer
valid (since the assumption is that they have been freed).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@...el.com>
Cc: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Jason Baron <jbaron@...mai.com>
---
 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;
 }
-late_initcall(jump_label_test);
+early_initcall(jump_label_test);
 #endif /* STATIC_KEYS_SELFTEST */

 #endif /* HAVE_JUMP_LABEL */
-- 
2.6.1