locking/core: Remove {read,spin,write}_can_lock()

Outside of the locking code itself, {read,spin,write}_can_lock() have no
users in tree. Apparmor (the last remaining user of write_can_lock()) got
moved over to lockdep by the previous patch.

This patch removes the use of {read,spin,write}_can_lock() from the
BUILD_LOCK_OPS macro, deferring to the trylock operation for testing the
lock status, and subsequently removes the unused macros altogether. They
aren't guaranteed to work in a concurrent environment and can give
incorrect results in the case of qrwlock.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/1507055129-12300-2-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/alpha/include/asm/spinlock.h

@@ -54,16 +54,6 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
 
 /***********************************************************/
 
-static inline int arch_read_can_lock(arch_rwlock_t *lock)
-{
-	return (lock->lock & 1) == 0;
-}
-
-static inline int arch_write_can_lock(arch_rwlock_t *lock)
-{
-	return lock->lock == 0;
-}
-
 static inline void arch_read_lock(arch_rwlock_t *lock)
 {
 	long regx;

arch/arc/include/asm/spinlock.h

@@ -410,9 +410,6 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
 
 #endif
 
-#define arch_read_can_lock(x)	((x)->counter > 0)
-#define arch_write_can_lock(x)	((x)->counter == __ARCH_RW_LOCK_UNLOCKED__)
-
 #define arch_read_lock_flags(lock, flags)	arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags)	arch_write_lock(lock)
 

arch/arm/include/asm/spinlock.h

@@ -193,9 +193,6 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
 	dsb_sev();
 }
 
-/* write_can_lock - would write_trylock() succeed? */
-#define arch_write_can_lock(x)		(ACCESS_ONCE((x)->lock) == 0)
-
 /*
  * Read locks are a bit more hairy:
  *  - Exclusively load the lock value.
@@ -273,9 +270,6 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
 	}
 }
 
-/* read_can_lock - would read_trylock() succeed? */
-#define arch_read_can_lock(x)		(ACCESS_ONCE((x)->lock) < 0x80000000)
-
 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 

arch/blackfin/include/asm/spinlock.h

@@ -48,16 +48,6 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
 	__raw_spin_unlock_asm(&lock->lock);
 }
 
-static inline int arch_read_can_lock(arch_rwlock_t *rw)
-{
-	return __raw_uncached_fetch_asm(&rw->lock) > 0;
-}
-
-static inline int arch_write_can_lock(arch_rwlock_t *rw)
-{
-	return __raw_uncached_fetch_asm(&rw->lock) == RW_LOCK_BIAS;
-}
-
 static inline void arch_read_lock(arch_rwlock_t *rw)
 {
 	__raw_read_lock_asm(&rw->lock);

arch/hexagon/include/asm/spinlock.h

@@ -86,16 +86,6 @@ static inline int arch_read_trylock(arch_rwlock_t *lock)
 	return temp;
 }
 
-static inline int arch_read_can_lock(arch_rwlock_t *rwlock)
-{
-	return rwlock->lock == 0;
-}
-
-static inline int arch_write_can_lock(arch_rwlock_t *rwlock)
-{
-	return rwlock->lock == 0;
-}
-
 /*  Stuffs a -1 in the lock value?  */
 static inline void arch_write_lock(arch_rwlock_t *lock)
 {

arch/ia64/include/asm/spinlock.h

@@ -127,9 +127,6 @@ static __always_inline void arch_spin_lock_flags(arch_spinlock_t *lock,
 	arch_spin_lock(lock);
 }
 
-#define arch_read_can_lock(rw)		(*(volatile int *)(rw) >= 0)
-#define arch_write_can_lock(rw)	(*(volatile int *)(rw) == 0)
-
 #ifdef ASM_SUPPORTED
 
 static __always_inline void

arch/m32r/include/asm/spinlock.h

@@ -137,18 +137,6 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
  * semaphore.h for details.  -ben
  */
 
-/**
- * read_can_lock - would read_trylock() succeed?
- * @lock: the rwlock in question.
- */
-#define arch_read_can_lock(x) ((int)(x)->lock > 0)
-
-/**
- * write_can_lock - would write_trylock() succeed?
- * @lock: the rwlock in question.
- */
-#define arch_write_can_lock(x) ((x)->lock == RW_LOCK_BIAS)
-
 static inline void arch_read_lock(arch_rwlock_t *rw)
 {
 	unsigned long tmp0, tmp1;

arch/metag/include/asm/spinlock_lnkget.h

@@ -136,21 +136,6 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
 		      : "memory");
 }
 
-/* write_can_lock - would write_trylock() succeed? */
-static inline int arch_write_can_lock(arch_rwlock_t *rw)
-{
-	int ret;
-
-	asm volatile ("LNKGETD	%0, [%1]\n"
-		      "CMP	%0, #0\n"
-		      "MOV	%0, #1\n"
-		      "XORNZ     %0, %0, %0\n"
-		      : "=&d" (ret)
-		      : "da" (&rw->lock)
-		      : "cc");
-	return ret;
-}
-
 /*
  * Read locks are a bit more hairy:
  *  - Exclusively load the lock value.
@@ -224,21 +209,6 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
 	return tmp;
 }
 
-/* read_can_lock - would read_trylock() succeed? */
-static inline int arch_read_can_lock(arch_rwlock_t *rw)
-{
-	int tmp;
-
-	asm volatile ("LNKGETD	%0, [%1]\n"
-		      "CMP	%0, %2\n"
-		      "MOV	%0, #1\n"
-		      "XORZ	%0, %0, %0\n"
-		      : "=&d" (tmp)
-		      : "da" (&rw->lock), "bd" (0x80000000)
-		      : "cc");
-	return tmp;
-}
-
 #define	arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define	arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 

arch/metag/include/asm/spinlock_lock1.h

@@ -104,16 +104,6 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
 	rw->lock = 0;
 }
 
-/* write_can_lock - would write_trylock() succeed? */
-static inline int arch_write_can_lock(arch_rwlock_t *rw)
-{
-	unsigned int ret;
-
-	barrier();
-	ret = rw->lock;
-	return (ret == 0);
-}
-
 /*
  * Read locks are a bit more hairy:
  *  - Exclusively load the lock value.
@@ -171,14 +161,4 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
 	return (ret < 0x80000000);
 }
 
-/* read_can_lock - would read_trylock() succeed? */
-static inline int arch_read_can_lock(arch_rwlock_t *rw)
-{
-	unsigned int ret;
-
-	barrier();
-	ret = rw->lock;
-	return (ret < 0x80000000);
-}
-
 #endif /* __ASM_SPINLOCK_LOCK1_H */

arch/mn10300/include/asm/spinlock.h

@@ -98,18 +98,6 @@ static inline void arch_spin_lock_flags(arch_spinlock_t *lock,
  * read-locks.
  */
 
-/**
- * read_can_lock - would read_trylock() succeed?
- * @lock: the rwlock in question.
- */
-#define arch_read_can_lock(x) ((int)(x)->lock > 0)
-
-/**
- * write_can_lock - would write_trylock() succeed?
- * @lock: the rwlock in question.
- */
-#define arch_write_can_lock(x) ((x)->lock == RW_LOCK_BIAS)
-
 /*
  * On mn10300, we implement read-write locks as a 32-bit counter
  * with the high bit (sign) being the "contended" bit.

arch/parisc/include/asm/spinlock.h

@@ -168,24 +168,6 @@ static __inline__ int arch_write_trylock(arch_rwlock_t *rw)
 	return result;
 }
 
-/*
- * read_can_lock - would read_trylock() succeed?
- * @lock: the rwlock in question.
- */
-static __inline__ int arch_read_can_lock(arch_rwlock_t *rw)
-{
-	return rw->counter >= 0;
-}
-
-/*
- * write_can_lock - would write_trylock() succeed?
- * @lock: the rwlock in question.
- */
-static __inline__ int arch_write_can_lock(arch_rwlock_t *rw)
-{
-	return !rw->counter;
-}
-
 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 

arch/powerpc/include/asm/spinlock.h

@@ -181,9 +181,6 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
  * read-locks.
  */
 
-#define arch_read_can_lock(rw)		((rw)->lock >= 0)
-#define arch_write_can_lock(rw)	(!(rw)->lock)
-
 #ifdef CONFIG_PPC64
 #define __DO_SIGN_EXTEND	"extsw	%0,%0\n"
 #define WRLOCK_TOKEN		LOCK_TOKEN	/* it's negative */

arch/s390/include/asm/spinlock.h

@@ -110,18 +110,6 @@ static inline void arch_spin_unlock(arch_spinlock_t *lp)
  * read-locks.
  */
 
-/**
- * read_can_lock - would read_trylock() succeed?
- * @lock: the rwlock in question.
- */
-#define arch_read_can_lock(x) ((int)(x)->lock >= 0)
-
-/**
- * write_can_lock - would write_trylock() succeed?
- * @lock: the rwlock in question.
- */
-#define arch_write_can_lock(x) ((x)->lock == 0)
-
 extern int _raw_read_trylock_retry(arch_rwlock_t *lp);
 extern int _raw_write_trylock_retry(arch_rwlock_t *lp);
 

arch/sh/include/asm/spinlock-cas.h

@@ -53,18 +53,6 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
  * read-locks.
  */
 
-/**
- * read_can_lock - would read_trylock() succeed?
- * @lock: the rwlock in question.
- */
-#define arch_read_can_lock(x)	((x)->lock > 0)
-
-/**
- * write_can_lock - would write_trylock() succeed?
- * @lock: the rwlock in question.
- */
-#define arch_write_can_lock(x)	((x)->lock == RW_LOCK_BIAS)
-
 static inline void arch_read_lock(arch_rwlock_t *rw)
 {
 	unsigned old;

arch/sh/include/asm/spinlock-llsc.h

@@ -89,18 +89,6 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
  * read-locks.
  */
 
-/**
- * read_can_lock - would read_trylock() succeed?
- * @lock: the rwlock in question.
- */
-#define arch_read_can_lock(x)	((x)->lock > 0)
-
-/**
- * write_can_lock - would write_trylock() succeed?
- * @lock: the rwlock in question.
- */
-#define arch_write_can_lock(x)	((x)->lock == RW_LOCK_BIAS)
-
 static inline void arch_read_lock(arch_rwlock_t *rw)
 {
 	unsigned long tmp;

arch/sparc/include/asm/spinlock_32.h

@@ -190,9 +190,6 @@ static inline int __arch_read_trylock(arch_rwlock_t *rw)
 #define arch_read_relax(lock)	cpu_relax()
 #define arch_write_relax(lock)	cpu_relax()
 
-#define arch_read_can_lock(rw) (!((rw)->lock & 0xff))
-#define arch_write_can_lock(rw) (!(rw)->lock)
-
 #endif /* !(__ASSEMBLY__) */
 
 #endif /* __SPARC_SPINLOCK_H */

arch/tile/include/asm/spinlock_32.h

@@ -79,22 +79,6 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
 #define _RD_COUNT_SHIFT 24
 #define _RD_COUNT_WIDTH 8
 
-/**
- * arch_read_can_lock() - would read_trylock() succeed?
- */
-static inline int arch_read_can_lock(arch_rwlock_t *rwlock)
-{
-	return (rwlock->lock << _RD_COUNT_WIDTH) == 0;
-}
-
-/**
- * arch_write_can_lock() - would write_trylock() succeed?
- */
-static inline int arch_write_can_lock(arch_rwlock_t *rwlock)
-{
-	return rwlock->lock == 0;
-}
-
 /**
  * arch_read_lock() - acquire a read lock.
  */

arch/tile/include/asm/spinlock_64.h

@@ -93,24 +93,6 @@ static inline int arch_write_val_locked(int val)
 	return val < 0;  /* Optimize "val & __WRITE_LOCK_BIT". */
 }
 
-/**
- * read_can_lock - would read_trylock() succeed?
- * @lock: the rwlock in question.
- */
-static inline int arch_read_can_lock(arch_rwlock_t *rw)
-{
-	return !arch_write_val_locked(rw->lock);
-}
-
-/**
- * write_can_lock - would write_trylock() succeed?
- * @lock: the rwlock in question.
- */
-static inline int arch_write_can_lock(arch_rwlock_t *rw)
-{
-	return rw->lock == 0;
-}
-
 extern void __read_lock_failed(arch_rwlock_t *rw);
 
 static inline void arch_read_lock(arch_rwlock_t *rw)

arch/xtensa/include/asm/spinlock.h

@@ -97,8 +97,6 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
  *  0x80000000  one writer owns the rwlock, no other writers, no readers
  */
 
-#define arch_write_can_lock(x)  ((x)->lock == 0)
-
 static inline void arch_write_lock(arch_rwlock_t *rw)
 {
 	unsigned long tmp;

include/asm-generic/qrwlock.h

@@ -52,24 +52,6 @@
 extern void queued_read_lock_slowpath(struct qrwlock *lock, u32 cnts);
 extern void queued_write_lock_slowpath(struct qrwlock *lock);
 
-/**
- * queued_read_can_lock- would read_trylock() succeed?
- * @lock: Pointer to queue rwlock structure
- */
-static inline int queued_read_can_lock(struct qrwlock *lock)
-{
-	return !(atomic_read(&lock->cnts) & _QW_WMASK);
-}
-
-/**
- * queued_write_can_lock- would write_trylock() succeed?
- * @lock: Pointer to queue rwlock structure
- */
-static inline int queued_write_can_lock(struct qrwlock *lock)
-{
-	return !atomic_read(&lock->cnts);
-}
-
 /**
  * queued_read_trylock - try to acquire read lock of a queue rwlock
  * @lock : Pointer to queue rwlock structure
@@ -169,8 +151,6 @@ static inline void queued_write_unlock(struct qrwlock *lock)
  * Remapping rwlock architecture specific functions to the corresponding
  * queue rwlock functions.
  */
-#define arch_read_can_lock(l)	queued_read_can_lock(l)
-#define arch_write_can_lock(l)	queued_write_can_lock(l)
 #define arch_read_lock(l)	queued_read_lock(l)
 #define arch_write_lock(l)	queued_write_lock(l)
 #define arch_read_trylock(l)	queued_read_trylock(l)