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>

4 files changed, 0 insertions, 37 deletions

diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h
index 7d026bf..5092532 100644
--- a/include/asm-generic/qrwlock.h
+++ b/include/asm-generic/qrwlock.h
@@ -53,24 +53,6 @@ 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
  * Return: 1 if lock acquired, 0 if failed
@@ -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)
diff --git a/include/linux/rwlock.h b/include/linux/rwlock.h
index bc2994e..766c5ca 100644
--- a/include/linux/rwlock.h
+++ b/include/linux/rwlock.h
@@ -50,9 +50,6 @@ do {								\
 # define do_raw_write_unlock(rwlock)	do {arch_write_unlock(&(rwlock)->raw_lock); __release(lock); } while (0)
 #endif
 
-#define read_can_lock(rwlock)		arch_read_can_lock(&(rwlock)->raw_lock)
-#define write_can_lock(rwlock)		arch_write_can_lock(&(rwlock)->raw_lock)
-
 /*
  * Define the various rw_lock methods.  Note we define these
  * regardless of whether CONFIG_SMP or CONFIG_PREEMPT are set. The various
diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index 69e079c..1e3e480 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -278,12 +278,6 @@ static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
 	1 : ({ local_irq_restore(flags); 0; }); \
 })
 
-/**
- * raw_spin_can_lock - would raw_spin_trylock() succeed?
- * @lock: the spinlock in question.
- */
-#define raw_spin_can_lock(lock)	(!raw_spin_is_locked(lock))
-
 /* Include rwlock functions */
 #include <linux/rwlock.h>
 
@@ -396,11 +390,6 @@ static __always_inline int spin_is_contended(spinlock_t *lock)
 	return raw_spin_is_contended(&lock->rlock);
 }
 
-static __always_inline int spin_can_lock(spinlock_t *lock)
-{
-	return raw_spin_can_lock(&lock->rlock);
-}
-
 #define assert_spin_locked(lock)	assert_raw_spin_locked(&(lock)->rlock)
 
 /*
diff --git a/include/linux/spinlock_up.h b/include/linux/spinlock_up.h
index 612fb53..901cf8f 100644
--- a/include/linux/spinlock_up.h
+++ b/include/linux/spinlock_up.h
@@ -77,7 +77,4 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
 
 #define arch_spin_is_contended(lock)	(((void)(lock), 0))
 
-#define arch_read_can_lock(lock)	(((void)(lock), 1))
-#define arch_write_can_lock(lock)	(((void)(lock), 1))
-
 #endif /* __LINUX_SPINLOCK_UP_H */