linux-kernel - [tip:locking/urgent] jump_label: Invoke jump_label_test() via early

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Date:   Tue, 14 Nov 2017 01:32:08 -0800
From:   tip-bot for Jason Baron <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...nel.org, rostedt@...dmis.org, paulmck@...ux.vnet.ibm.com,
        hpa@...or.com, torvalds@...ux-foundation.org, tglx@...utronix.de,
        jbaron@...mai.com, fengguang.wu@...el.com
Subject: [tip:locking/urgent] jump_label: Invoke jump_label_test() via
 early_initcall()

Commit-ID:  92ee46efeb505ead3ab06d3c5ce695637ed5f152
Gitweb:     https://git.kernel.org/tip/92ee46efeb505ead3ab06d3c5ce695637ed5f152
Author:     Jason Baron <jbaron@...mai.com>
AuthorDate: Mon, 13 Nov 2017 16:48:47 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 14 Nov 2017 08:41:41 +0100

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greter than or equal to SYSTEM_RUNNING then __init sections are no longer
valid (since the assumption is that they have been freed).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>
Signed-off-by: Jason Baron <jbaron@...mai.com>
Acked-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1510609727-2238-1-git-send-email-jbaron@akamai.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 8ff4ca4..8594d24 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 */