linux-kernel - [PATCH] paravirt/locks: avoid modifying static key before jump_label

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Message-Id: <20171023134948.24886-1-jgross@suse.com>
Date:   Mon, 23 Oct 2017 15:49:48 +0200
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     hpa@...or.com, tglx@...utronix.de, mingo@...hat.com, arnd@...db.de,
        peterz@...radead.org, Juergen Gross <jgross@...e.com>
Subject: [PATCH] paravirt/locks: avoid modifying static key before jump_label_init()

Don't try to set the static virt_spin_lock_key to a value before
jump_label_init() has been called, as this will result in a WARN().

Solve the problem by introducing a new lock_init() hook called after
jump_label_init() instead of doing the call inside of
smp_prepare_boot_cpu().

Signed-off-by: Juergen Gross <jgross@...e.com>
---
Based on kernel/git/tip/tip.git locking/core
---
 arch/x86/include/asm/qspinlock.h | 5 +----
 arch/x86/kernel/smpboot.c        | 1 -
 include/asm-generic/qspinlock.h  | 6 ++++++
 include/linux/spinlock.h         | 4 ++++
 include/linux/spinlock_up.h      | 4 ++++
 init/main.c                      | 2 ++
 kernel/locking/spinlock.c        | 7 +++++++
 7 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h
index 308dfd0714c7..a53ef9ed0dc1 100644
--- a/arch/x86/include/asm/qspinlock.h
+++ b/arch/x86/include/asm/qspinlock.h
@@ -49,6 +49,7 @@ static inline void queued_spin_unlock(struct qspinlock *lock)
 #ifdef CONFIG_PARAVIRT
 DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key);
 
+#define native_pv_lock_init native_pv_lock_init
 void native_pv_lock_init(void) __init;
 
 #define virt_spin_lock virt_spin_lock
@@ -70,10 +71,6 @@ static inline bool virt_spin_lock(struct qspinlock *lock)
 
 	return true;
 }
-#else
-static inline void native_pv_lock_init(void)
-{
-}
 #endif /* CONFIG_PARAVIRT */
 
 #include <asm-generic/qspinlock.h>
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 361f91674ce5..55a3121dd479 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1385,7 +1385,6 @@ void __init native_smp_prepare_boot_cpu(void)
 	/* already set me in cpu_online_mask in boot_cpu_init() */
 	cpumask_set_cpu(me, cpu_callout_mask);
 	cpu_set_state_online(me);
-	native_pv_lock_init();
 }
 
 void __init native_smp_cpus_done(unsigned int max_cpus)
diff --git a/include/asm-generic/qspinlock.h b/include/asm-generic/qspinlock.h
index 66260777d644..42784a353401 100644
--- a/include/asm-generic/qspinlock.h
+++ b/include/asm-generic/qspinlock.h
@@ -111,6 +111,12 @@ static __always_inline bool virt_spin_lock(struct qspinlock *lock)
 }
 #endif
 
+#ifndef native_pv_lock_init
+static __always_inline void native_pv_lock_init(void)
+{
+}
+#endif
+
 /*
  * Remapping spinlock architecture specific functions to the corresponding
  * queued spinlock functions.
diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index 69e079c5ff98..6654ff285e5c 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -420,4 +420,8 @@ extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
 #define atomic_dec_and_lock(atomic, lock) \
 		__cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
 
+#ifdef CONFIG_SMP
+void lock_init(void) __init;
+#endif
+
 #endif /* __LINUX_SPINLOCK_H */
diff --git a/include/linux/spinlock_up.h b/include/linux/spinlock_up.h
index 612fb530af41..bc4787900ad7 100644
--- a/include/linux/spinlock_up.h
+++ b/include/linux/spinlock_up.h
@@ -80,4 +80,8 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
 #define arch_read_can_lock(lock)	(((void)(lock), 1))
 #define arch_write_can_lock(lock)	(((void)(lock), 1))
 
+static inline lock_init(void)
+{
+}
+
 #endif /* __LINUX_SPINLOCK_UP_H */
diff --git a/init/main.c b/init/main.c
index 0ee9c6866ada..e5c9f9bcd311 100644
--- a/init/main.c
+++ b/init/main.c
@@ -88,6 +88,7 @@
 #include <linux/io.h>
 #include <linux/cache.h>
 #include <linux/rodata_test.h>
+#include <linux/spinlock.h>
 
 #include <asm/io.h>
 #include <asm/bugs.h>
@@ -567,6 +568,7 @@ asmlinkage __visible void __init start_kernel(void)
 	sort_main_extable();
 	trap_init();
 	mm_init();
+	lock_init();
 
 	ftrace_init();
 
diff --git a/kernel/locking/spinlock.c b/kernel/locking/spinlock.c
index 4b082b5cac9e..f086e444c2ac 100644
--- a/kernel/locking/spinlock.c
+++ b/kernel/locking/spinlock.c
@@ -397,3 +397,10 @@ notrace int in_lock_functions(unsigned long addr)
 	&& addr < (unsigned long)__lock_text_end;
 }
 EXPORT_SYMBOL(in_lock_functions);
+
+void __init lock_init(void)
+{
+#ifdef CONFIG_QUEUED_SPINLOCKS
+	native_pv_lock_init();
+#endif
+}
-- 
2.12.3