From 9badbabee2f555e9722e7e48a4312e5b5038ba82 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <frederic@kernel.org>
Date: Mon, 6 Nov 2017 16:01:23 +0100
Subject: [PATCH] x86: Use lockdep to assert IRQs are disabled/enabled

References: bnc#1068202 Avoid irqs_disabled debugging checks in fast paths
Patch-mainline: v4.15-rc1
Git-commit: 7a10e2a9190628a4024ea394ce7bd641ae40ffd1

Use lockdep to check that IRQs are enabled or disabled as expected. This
way the sanity check only shows overhead when concurrency correctness
debug code is enabled.

It also makes no more sense to fix the IRQ flags when a bug is detected
as the assertion is now pure config-dependent debugging. And to quote
Peter Zijlstra:

	The whole if !disabled, disable logic is uber paranoid programming,
	but I don't think we've ever seen that WARN trigger, and if it does
	(and then burns the kernel) we at least know what happend.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: David S . Miller <davem@davemloft.net>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/1509980490-4285-8-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 arch/x86/entry/common.c   | 4 +---
 arch/x86/kernel/smpboot.c | 2 +-
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index cdefcfdd9e63..58e639190aab 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -183,9 +183,7 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
 	struct thread_info *ti = current_thread_info();
 	u32 cached_flags;
 
-	if (IS_ENABLED(CONFIG_PROVE_LOCKING) && WARN_ON(!irqs_disabled()))
-		local_irq_disable();
-
+	lockdep_assert_irqs_disabled();
 	lockdep_sys_exit();
 
 	cached_flags = READ_ONCE(ti->flags);
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 4899684fe181..4949ab5b8f34 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1097,7 +1097,7 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)
 	unsigned long flags;
 	int err;
 
-	WARN_ON(irqs_disabled());
+	lockdep_assert_irqs_enabled();
 
 	pr_debug("++++++++++++++++++++=_---CPU UP  %u\n", cpu);