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Date:	Sun, 24 Feb 2008 20:33:51 -0800
From:	David Brownell <david-b@...bell.net>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Linux Kernel list <linux-kernel@...r.kernel.org>, mingo@...hat.com
Subject: [patch 2.6.25-rc3] lockdep:  add spin_lock_irq_nested()

> > >     ==> LOCKDEP feature is evidently missing:
> > >             spin_lock_irq_nested(lock_ptr, lock_class)
> > 
> > This rant is more lines than adding the API :-/ the reason for it not
> > being there is simple, it wasn't needed up until now.
> 
> I suspected that was the case, but for all I knew there was some
> religious objection. 

Does this look about right?  Or, I suppose it could just call
the _spin_lock_irqsave_nested() routine and discard the result.

- Dave

=========	 CUT HERE
Add new spin_lock_irq_nested() call, so that lockdep can work with the
code which uses spin_*_irq() calls that don't save/restore flags.

Signed-off-by: David Brownell <dbrownell@...rs.sourceforge.net>
---
Against 2.6.25-rc3

 include/linux/spinlock.h         |    6 ++++++
 include/linux/spinlock_api_smp.h |    2 ++
 kernel/spinlock.c                |   21 +++++++++++++++++++--
 3 files changed, 27 insertions(+), 2 deletions(-)

--- a/include/linux/spinlock.h	2008-02-24 18:50:50.000000000 -0800
+++ b/include/linux/spinlock.h	2008-02-24 19:02:39.000000000 -0800
@@ -196,9 +196,13 @@ do {								\
 #define write_lock_irqsave(lock, flags)	flags = _write_lock_irqsave(lock)
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
+#define spin_lock_irq_nested(lock, subclass) \
+	_spin_lock_irq_nested(lock, subclass)
 #define spin_lock_irqsave_nested(lock, flags, subclass) \
 	flags = _spin_lock_irqsave_nested(lock, subclass)
 #else
+#define spin_lock_irq_nested(lock, subclass) \
+	_spin_lock_irq(lock)
 #define spin_lock_irqsave_nested(lock, flags, subclass) \
 	flags = _spin_lock_irqsave(lock)
 #endif
@@ -208,6 +212,8 @@ do {								\
 #define spin_lock_irqsave(lock, flags)	_spin_lock_irqsave(lock, flags)
 #define read_lock_irqsave(lock, flags)	_read_lock_irqsave(lock, flags)
 #define write_lock_irqsave(lock, flags)	_write_lock_irqsave(lock, flags)
+#define spin_lock_irq_nested(lock, subclass) \
+	spin_lock_irq(lock)
 #define spin_lock_irqsave_nested(lock, flags, subclass)	\
 	spin_lock_irqsave(lock, flags)
 
--- a/include/linux/spinlock_api_smp.h	2008-02-24 18:50:50.000000000 -0800
+++ b/include/linux/spinlock_api_smp.h	2008-02-24 19:02:39.000000000 -0800
@@ -28,6 +28,8 @@ void __lockfunc _spin_lock_bh(spinlock_t
 void __lockfunc _read_lock_bh(rwlock_t *lock)		__acquires(lock);
 void __lockfunc _write_lock_bh(rwlock_t *lock)		__acquires(lock);
 void __lockfunc _spin_lock_irq(spinlock_t *lock)	__acquires(lock);
+void __lockfunc _spin_lock_irq_nested(spinlock_t *lock, int subclass)
+							__acquires(lock);
 void __lockfunc _read_lock_irq(rwlock_t *lock)		__acquires(lock);
 void __lockfunc _write_lock_irq(rwlock_t *lock)		__acquires(lock);
 unsigned long __lockfunc _spin_lock_irqsave(spinlock_t *lock)
--- a/kernel/spinlock.c	2008-02-24 18:50:50.000000000 -0800
+++ b/kernel/spinlock.c	2008-02-24 19:02:39.000000000 -0800
@@ -290,8 +290,26 @@ void __lockfunc _spin_lock_nested(spinlo
 	spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
 	LOCK_CONTENDED(lock, _raw_spin_trylock, _raw_spin_lock);
 }
-
 EXPORT_SYMBOL(_spin_lock_nested);
+
+void __lockfunc _spin_lock_irq_nested(spinlock_t *lock, int subclass)
+{
+	local_irq_disable();
+	preempt_disable();
+	spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
+	/*
+	 * On lockdep we dont want the hand-coded irq-enable of
+	 * _raw_spin_lock_flags() code, because lockdep assumes
+	 * that interrupts are not re-enabled during lock-acquire:
+	 */
+#ifdef CONFIG_LOCKDEP
+	LOCK_CONTENDED(lock, _raw_spin_trylock, _raw_spin_lock);
+#else
+	_raw_spin_lock_flags(lock, &flags);
+#endif
+}
+EXPORT_SYMBOL(_spin_lock_irq_nested);
+
 unsigned long __lockfunc _spin_lock_irqsave_nested(spinlock_t *lock, int subclass)
 {
 	unsigned long flags;
@@ -311,7 +329,6 @@ unsigned long __lockfunc _spin_lock_irqs
 #endif
 	return flags;
 }
-
 EXPORT_SYMBOL(_spin_lock_irqsave_nested);
 
 #endif
--
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