linux-kernel - [PATCH [RT] 02/14] spinlock: make preemptible-waiter feature a specific config option

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Date:	Thu, 21 Feb 2008 10:26:36 -0500
From:	Gregory Haskins <ghaskins@...ell.com>
To:	mingo@...e.hu, a.p.zijlstra@...llo.nl, tglx@...utronix.de,
	rostedt@...dmis.org, linux-rt-users@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, bill.huey@...il.com,
	kevin@...man.org, cminyard@...sta.com, dsingleton@...sta.com,
	dwalker@...sta.com, npiggin@...e.de, dsaxena@...xity.net,
	ak@...e.de, gregkh@...e.de, sdietrich@...ell.com,
	pmorreale@...ell.com, mkohari@...ell.com, ghaskins@...ell.com
Subject: [PATCH [RT] 02/14] spinlock: make preemptible-waiter feature a
	specific config option

We introduce a configuration variable for the feature to make it easier for
various architectures and/or configs to enable or disable it based on their
requirements.  

Signed-off-by: Gregory Haskins <ghaskins@...ell.com>
---

 kernel/Kconfig.preempt |    9 +++++++++
 kernel/spinlock.c      |    7 +++----
 lib/Kconfig.debug      |    1 +
 3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index 41a0d88..5b45213 100644
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -86,6 +86,15 @@ config PREEMPT
 	default y
 	depends on PREEMPT_DESKTOP || PREEMPT_RT
 
+config DISABLE_PREEMPT_SPINLOCK_WAITERS
+        bool
+	default n
+
+config PREEMPT_SPINLOCK_WAITERS
+        bool
+	default y
+	depends on PREEMPT && SMP && !DISABLE_PREEMPT_SPINLOCK_WAITERS
+
 config PREEMPT_SOFTIRQS
 	bool "Thread Softirqs"
 	default n
diff --git a/kernel/spinlock.c b/kernel/spinlock.c
index b0e7f02..2e6a904 100644
--- a/kernel/spinlock.c
+++ b/kernel/spinlock.c
@@ -116,8 +116,7 @@ EXPORT_SYMBOL(__write_trylock_irqsave);
  * even on CONFIG_PREEMPT, because lockdep assumes that interrupts are
  * not re-enabled during lock-acquire (which the preempt-spin-ops do):
  */
-#if !defined(CONFIG_PREEMPT) || !defined(CONFIG_SMP) || \
-	defined(CONFIG_DEBUG_LOCK_ALLOC)
+#if !defined(CONFIG_PREEMPT_SPINLOCK_WAITERS)
 
 void __lockfunc __read_lock(raw_rwlock_t *lock)
 {
@@ -244,7 +243,7 @@ void __lockfunc __write_lock(raw_rwlock_t *lock)
 
 EXPORT_SYMBOL(__write_lock);
 
-#else /* CONFIG_PREEMPT: */
+#else /* CONFIG_PREEMPT_SPINLOCK_WAITERS */
 
 /*
  * This could be a long-held lock. We both prepare to spin for a long
@@ -334,7 +333,7 @@ BUILD_LOCK_OPS(spin, raw_spinlock);
 BUILD_LOCK_OPS(read, raw_rwlock);
 BUILD_LOCK_OPS(write, raw_rwlock);
 
-#endif /* CONFIG_PREEMPT */
+#endif /* CONFIG_PREEMPT_SPINLOCK_WAITERS */
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9208791..f2889b2 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -233,6 +233,7 @@ config DEBUG_LOCK_ALLOC
 	bool "Lock debugging: detect incorrect freeing of live locks"
 	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 	select DEBUG_SPINLOCK
+	select DISABLE_PREEMPT_SPINLOCK_WAITERS
 	select DEBUG_MUTEXES
 	select LOCKDEP
 	help

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