From: David Woodhouse <dwmw2@infradead.org>

Debgging infrastructure to drop a stack trace if someone calls one of the
sleep_on() functions without lock_kernel() held.



---

 include/linux/smp_lock.h |    4 +++-
 kernel/sched.c           |   15 +++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff -puN include/linux/smp_lock.h~sleep_on-needs_lock_kernel include/linux/smp_lock.h
--- 25/include/linux/smp_lock.h~sleep_on-needs_lock_kernel	2004-02-06 18:52:50.000000000 -0800
+++ 25-akpm/include/linux/smp_lock.h	2004-02-06 18:52:50.000000000 -0800
@@ -5,7 +5,9 @@
 #include <linux/sched.h>
 #include <linux/spinlock.h>
 
-#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
+#define BKL_DEBUG /* For testing for sleep_on() abuse */
+
+#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT) || defined(BKL_DEBUG)
 
 extern spinlock_t kernel_flag;
 
diff -puN kernel/sched.c~sleep_on-needs_lock_kernel kernel/sched.c
--- 25/kernel/sched.c~sleep_on-needs_lock_kernel	2004-02-06 18:52:50.000000000 -0800
+++ 25-akpm/kernel/sched.c	2004-02-06 18:52:50.000000000 -0800
@@ -2219,10 +2219,21 @@ EXPORT_SYMBOL(wait_for_completion);
 	__remove_wait_queue(q, &wait);			\
 	spin_unlock_irqrestore(&q->lock, flags);
 
+#define SLEEP_ON_BKLCHECK				\
+	if (unlikely(!kernel_locked()) &&		\
+	    sleep_on_bkl_warnings < 10) {		\
+		sleep_on_bkl_warnings++;		\
+		WARN_ON(1);				\
+	}
+
+static int sleep_on_bkl_warnings;
+
 void interruptible_sleep_on(wait_queue_head_t *q)
 {
 	SLEEP_ON_VAR
 
+	SLEEP_ON_BKLCHECK
+
 	current->state = TASK_INTERRUPTIBLE;
 
 	SLEEP_ON_HEAD
@@ -2236,6 +2247,8 @@ long interruptible_sleep_on_timeout(wait
 {
 	SLEEP_ON_VAR
 
+	SLEEP_ON_BKLCHECK
+
 	current->state = TASK_INTERRUPTIBLE;
 
 	SLEEP_ON_HEAD
@@ -2251,6 +2264,8 @@ void sleep_on(wait_queue_head_t *q)
 {
 	SLEEP_ON_VAR
 
+	SLEEP_ON_BKLCHECK
+
 	current->state = TASK_UNINTERRUPTIBLE;
 
 	SLEEP_ON_HEAD

_