[PATCH] might_sleep() improvements

From: Mitchell Blank Jr <mitch@sfgoth.com>

This patch makes the following improvements to might_sleep():

 o Add a "might_sleep_if()" macro for when we might sleep only if some
   condition is met.  It's a bit tidier, and has an unlikely() in it.

 o Add might_sleep checks to skb_share_check() and skb_unshare() which
   sometimes need to allocate memory.

 o Make all architectures call might_sleep() in both down() and
   down_interruptible().  Before only ppc, ppc64, and i386 did this check.
   (sh did the check on down() but not down_interruptible())

arch/sparc64/kernel/semaphore.c

@@ -110,6 +110,7 @@ static void __down(struct semaphore * sem)
 
 void down(struct semaphore *sem)
 {
+	might_sleep();
 	/* This atomically does:
 	 * 	old_val = sem->count;
 	 *	new_val = sem->count - 1;
@@ -219,6 +220,7 @@ int down_interruptible(struct semaphore *sem)
 {
 	int ret = 0;
 	
+	might_sleep();
 	/* This atomically does:
 	 * 	old_val = sem->count;
 	 *	new_val = sem->count - 1;

include/asm-alpha/semaphore.h

@@ -88,14 +88,18 @@ extern void __up_wakeup(struct semaphore *);
 
 static inline void __down(struct semaphore *sem)
 {
-	long count = atomic_dec_return(&sem->count);
+	long count;
+	might_sleep();
+	count = atomic_dec_return(&sem->count);
 	if (unlikely(count < 0))
 		__down_failed(sem);
 }
 
 static inline int __down_interruptible(struct semaphore *sem)
 {
-	long count = atomic_dec_return(&sem->count);
+	long count;
+	might_sleep();
+	count = atomic_dec_return(&sem->count);
 	if (unlikely(count < 0))
 		return __down_failed_interruptible(sem);
 	return 0;

include/asm-arm/semaphore.h

@@ -88,7 +88,7 @@ static inline void down(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
-
+	might_sleep();
 	__down_op(sem, __down_failed);
 }
 
@@ -101,7 +101,7 @@ static inline int down_interruptible (struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
-
+	might_sleep();
 	return __down_op_ret(sem, __down_interruptible_failed);
 }
 

include/asm-arm26/semaphore.h

@@ -84,7 +84,7 @@ static inline void down(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
-
+	might_sleep();
 	__down_op(sem, __down_failed);
 }
 
@@ -97,7 +97,7 @@ static inline int down_interruptible (struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
-
+	might_sleep();
 	return __down_op_ret(sem, __down_interruptible_failed);
 }
 

include/asm-cris/semaphore.h

@@ -79,6 +79,7 @@ extern inline void down(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
+	might_sleep();
 
 	/* atomically decrement the semaphores count, and if its negative, we wait */
 	local_save_flags(flags);
@@ -104,6 +105,7 @@ extern inline int down_interruptible(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
+	might_sleep();
 
 	/* atomically decrement the semaphores count, and if its negative, we wait */
 	local_save_flags(flags);

include/asm-h8300/semaphore.h

@@ -90,6 +90,7 @@ static inline void down(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
+	might_sleep();
 
 	count = &(sem->count);
 	__asm__ __volatile__(
@@ -117,6 +118,7 @@ static inline int down_interruptible(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
+	might_sleep();
 
 	count = &(sem->count);
 	__asm__ __volatile__(

include/asm-ia64/semaphore.h

@@ -73,6 +73,7 @@ down (struct semaphore *sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
+	might_sleep();
 	if (atomic_dec_return(&sem->count) < 0)
 		__down(sem);
 }
@@ -89,6 +90,7 @@ down_interruptible (struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
+	might_sleep();
 	if (atomic_dec_return(&sem->count) < 0)
 		ret = __down_interruptible(sem);
 	return ret;

include/asm-m68k/semaphore.h

@@ -89,7 +89,7 @@ extern inline void down(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
-
+	might_sleep();
 	__asm__ __volatile__(
 		"| atomic down operation\n\t"
 		"subql #1,%0@\n\t"
@@ -112,7 +112,7 @@ extern inline int down_interruptible(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
-
+	might_sleep();
 	__asm__ __volatile__(
 		"| atomic interruptible down operation\n\t"
 		"subql #1,%1@\n\t"

include/asm-m68knommu/semaphore.h

@@ -88,7 +88,7 @@ extern inline void down(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
-
+	might_sleep();
 	__asm__ __volatile__(
 		"| atomic down operation\n\t"
 		"movel	%0, %%a1\n\t"
@@ -108,7 +108,7 @@ extern inline int down_interruptible(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
-
+	might_sleep();
 	__asm__ __volatile__(
 		"| atomic down operation\n\t"
 		"movel	%1, %%a1\n\t"

include/asm-mips/semaphore.h

@@ -88,6 +88,7 @@ static inline void down(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
+	might_sleep();
 	if (atomic_dec_return(&sem->count) < 0)
 		__down(sem);
 }
@@ -103,6 +104,7 @@ static inline int down_interruptible(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
+	might_sleep();
 	if (atomic_dec_return(&sem->count) < 0)
 		ret = __down_interruptible(sem);
 	return ret;

include/asm-parisc/semaphore.h

@@ -84,7 +84,7 @@ extern __inline__ void down(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
-
+	might_sleep();
 	spin_lock_irq(&sem->sentry);
 	if (sem->count > 0) {
 		sem->count--;
@@ -100,7 +100,7 @@ extern __inline__ int down_interruptible(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
-
+	might_sleep();
 	spin_lock_irq(&sem->sentry);
 	if (sem->count > 0) {
 		sem->count--;

include/asm-s390/semaphore.h

@@ -60,6 +60,7 @@ asmlinkage void __up(struct semaphore * sem);
 
 static inline void down(struct semaphore * sem)
 {
+	might_sleep();
 	if (atomic_dec_return(&sem->count) < 0)
 		__down(sem);
 }
@@ -68,6 +69,7 @@ static inline int down_interruptible(struct semaphore * sem)
 {
 	int ret = 0;
 
+	might_sleep();
 	if (atomic_dec_return(&sem->count) < 0)
 		ret = __down_interruptible(sem);
 	return ret;

include/asm-sh/semaphore.h

@@ -107,6 +107,7 @@ static inline int down_interruptible(struct semaphore * sem)
 	CHECK_MAGIC(sem->__magic);
 #endif
 
+	might_sleep();
 	if (atomic_dec_return(&sem->count) < 0)
 		ret = __down_interruptible(sem);
 	return ret;

include/asm-sparc/semaphore.h

@@ -71,6 +71,7 @@ static inline void down(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
+	might_sleep();
 
 	ptr = &(sem->count.counter);
 	increment = 1;
@@ -107,6 +108,7 @@ static inline int down_interruptible(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
+	might_sleep();
 
 	ptr = &(sem->count.counter);
 	increment = 1;

include/asm-v850/semaphore.h

@@ -57,6 +57,7 @@ extern void __up (struct semaphore * sem);
 
 extern inline void down (struct semaphore * sem)
 {
+	might_sleep();
 	if (atomic_dec_return (&sem->count) < 0)
 		__down (sem);
 }
@@ -64,6 +65,7 @@ extern inline void down (struct semaphore * sem)
 extern inline int down_interruptible (struct semaphore * sem)
 {
 	int ret = 0;
+	might_sleep();
 	if (atomic_dec_return (&sem->count) < 0)
 		ret = __down_interruptible (sem);
 	return ret;

include/asm-x86_64/semaphore.h

@@ -118,6 +118,7 @@ static inline void down(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
+	might_sleep();
 
 	__asm__ __volatile__(
 		"# atomic down operation\n\t"
@@ -144,6 +145,7 @@ static inline int down_interruptible(struct semaphore * sem)
 #if WAITQUEUE_DEBUG
 	CHECK_MAGIC(sem->__magic);
 #endif
+	might_sleep();
 
 	__asm__ __volatile__(
 		"# atomic interruptible down operation\n\t"

include/linux/kernel.h

@@ -52,8 +52,10 @@ struct completion;
 #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
 void __might_sleep(char *file, int line);
 #define might_sleep() __might_sleep(__FILE__, __LINE__)
+#define might_sleep_if(cond) do { if (unlikely(cond)) might_sleep(); } while (0)
 #else
 #define might_sleep() do {} while(0)
+#define might_sleep_if(cond) do {} while (0)
 #endif
 
 extern struct notifier_block *panic_notifier_list;

include/linux/skbuff.h

@@ -389,6 +389,7 @@ static inline int skb_shared(struct sk_buff *skb)
  */
 static inline struct sk_buff *skb_share_check(struct sk_buff *skb, int pri)
 {
+	might_sleep_if(pri & __GFP_WAIT);
 	if (skb_shared(skb)) {
 		struct sk_buff *nskb = skb_clone(skb, pri);
 		kfree_skb(skb);
@@ -419,6 +420,7 @@ static inline struct sk_buff *skb_share_check(struct sk_buff *skb, int pri)
  */
 static inline struct sk_buff *skb_unshare(struct sk_buff *skb, int pri)
 {
+	might_sleep_if(pri & __GFP_WAIT);
 	if (skb_cloned(skb)) {
 		struct sk_buff *nskb = skb_copy(skb, pri);
 		kfree_skb(skb);	/* Free our shared copy */

mm/page_alloc.c

@@ -543,8 +543,7 @@ __alloc_pages(unsigned int gfp_mask, unsigned int order,
 	int do_retry;
 	struct reclaim_state reclaim_state;
 
-	if (wait)
-		might_sleep();
+	might_sleep_if(wait);
 
 	cold = 0;
 	if (gfp_mask & __GFP_COLD)

mm/rmap.c

@@ -503,8 +503,7 @@ struct pte_chain *pte_chain_alloc(int gfp_flags)
 	struct pte_chain *ret;
 	struct pte_chain **pte_chainp;
 
-	if (gfp_flags & __GFP_WAIT)
-		might_sleep();
+	might_sleep_if(gfp_flags & __GFP_WAIT);
 
 	pte_chainp = &get_cpu_var(local_pte_chain);
 	if (*pte_chainp) {

mm/slab.c

@@ -1814,8 +1814,7 @@ static void* cache_alloc_refill(kmem_cache_t* cachep, int flags)
 static inline void
 cache_alloc_debugcheck_before(kmem_cache_t *cachep, int flags)
 {
-	if (flags & __GFP_WAIT)
-		might_sleep();
+	might_sleep_if(flags & __GFP_WAIT);
 #if DEBUG
 	kmem_flagcheck(cachep, flags);
 #endif