From: Robin Holt <holt@sgi.com>
Date: Thu, 2 Apr 2009 23:59:45 +0000 (-0700)
Subject: Factor out #ifdefs from kernel/spinlock.c to LOCK_CONTENDED_FLAGS
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=e8c158bb313c1df421eab7dc4299cd39cbbf5895;p=openwrt%2Fstaging%2Fblogic.git

Factor out #ifdefs from kernel/spinlock.c to LOCK_CONTENDED_FLAGS

SGI has observed that on large systems, interrupts are not serviced for a
long period of time when waiting for a rwlock.  The following patch series
re-enables irqs while waiting for the lock, resembling the code which is
already there for spinlocks.

I only made the ia64 version, because the patch adds some overhead to the
fast path.  I assume there is currently no demand to have this for other
architectures, because the systems are not so large.  Of course, the
possibility to implement raw_{read|write}_lock_flags for any architecture
is still there.

This patch:

The new macro LOCK_CONTENDED_FLAGS expands to the correct implementation
depending on the config options, so that IRQ's are re-enabled when
possible, but they remain disabled if CONFIG_LOCKDEP is set.

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Signed-off-by: Robin Holt <holt@sgi.com>
Cc: <linux-arch@vger.kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 5a58ea3e91e9..da5a5a1f4cd2 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -364,6 +364,23 @@ do {								\
 
 #endif /* CONFIG_LOCK_STAT */
 
+#ifdef CONFIG_LOCKDEP
+
+/*
+ * On lockdep we dont want the hand-coded irq-enable of
+ * _raw_*_lock_flags() code, because lockdep assumes
+ * that interrupts are not re-enabled during lock-acquire:
+ */
+#define LOCK_CONTENDED_FLAGS(_lock, try, lock, lockfl, flags) \
+	LOCK_CONTENDED((_lock), (try), (lock))
+
+#else /* CONFIG_LOCKDEP */
+
+#define LOCK_CONTENDED_FLAGS(_lock, try, lock, lockfl, flags) \
+	lockfl((_lock), (flags))
+
+#endif /* CONFIG_LOCKDEP */
+
 #ifdef CONFIG_GENERIC_HARDIRQS
 extern void early_init_irq_lock_class(void);
 #else
diff --git a/kernel/spinlock.c b/kernel/spinlock.c
index 29ab20749dd3..7283c6dc2d59 100644
--- a/kernel/spinlock.c
+++ b/kernel/spinlock.c
@@ -299,16 +299,8 @@ unsigned long __lockfunc _spin_lock_irqsave_nested(spinlock_t *lock, int subclas
 	local_irq_save(flags);
 	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
+	LOCK_CONTENDED_FLAGS(lock, _raw_spin_trylock, _raw_spin_lock,
+				_raw_spin_lock_flags, &flags);
 	return flags;
 }
 EXPORT_SYMBOL(_spin_lock_irqsave_nested);