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

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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 <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Will Deacon 2017-10-03 19:25:27 +01:00 • committed by Ingo Molnar
commit a8a217c221
24 changed files with 2 additions and 253 deletions
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16
arch/tile/include/asm/spinlock_32.h
View file

@ -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.
*/

18
arch/tile/include/asm/spinlock_64.h
View file

@ -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)