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>

2 files changed, 0 insertions, 34 deletions

diff --git a/arch/tile/include/asm/spinlock_32.h b/arch/tile/include/asm/spinlock_32.h
index cba8ba9b8da6..91d05f21cba9 100644
--- a/arch/tile/include/asm/spinlock_32.h
+++ b/arch/tile/include/asm/spinlock_32.h
@@ -80,22 +80,6 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
 #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.
  */
 void arch_read_lock(arch_rwlock_t *rwlock);
diff --git a/arch/tile/include/asm/spinlock_64.h b/arch/tile/include/asm/spinlock_64.h
index 9a2c2d605752..c802f48badf4 100644
--- a/arch/tile/include/asm/spinlock_64.h
+++ b/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)