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authorWill Deacon <will.deacon@arm.com>2018-06-19 13:53:12 +0100
committerIngo Molnar <mingo@kernel.org>2018-06-21 12:52:12 +0200
commit84c6591103dbeaf393a092a3fc7b09510825f6b9 (patch)
treea5c66f057f1ba7db4c9a4725b5827f40206f6d86
parente986a0d6cb36b54838b2f5f8ac2bb5f9baadd977 (diff)
locking/atomics, asm-generic/bitops/lock.h: Rewrite using atomic_fetch_*()
The lock bitops can be implemented more efficiently using the atomic_fetch_*() ops, which provide finer-grained control over the memory ordering semantics than the bitops. Signed-off-by: Will Deacon <will.deacon@arm.com> Acked-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: linux-arm-kernel@lists.infradead.org Cc: yamada.masahiro@socionext.com Link: https://lore.kernel.org/lkml/1529412794-17720-8-git-send-email-will.deacon@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--include/asm-generic/bitops/lock.h68
1 files changed, 56 insertions, 12 deletions
diff --git a/include/asm-generic/bitops/lock.h b/include/asm-generic/bitops/lock.h
index 67ab280ad134..3ae021368f48 100644
--- a/include/asm-generic/bitops/lock.h
+++ b/include/asm-generic/bitops/lock.h
@@ -2,6 +2,10 @@
#ifndef _ASM_GENERIC_BITOPS_LOCK_H_
#define _ASM_GENERIC_BITOPS_LOCK_H_
+#include <linux/atomic.h>
+#include <linux/compiler.h>
+#include <asm/barrier.h>
+
/**
* test_and_set_bit_lock - Set a bit and return its old value, for lock
* @nr: Bit to set
@@ -11,7 +15,20 @@
* the returned value is 0.
* It can be used to implement bit locks.
*/
-#define test_and_set_bit_lock(nr, addr) test_and_set_bit(nr, addr)
+static inline int test_and_set_bit_lock(unsigned int nr,
+ volatile unsigned long *p)
+{
+ long old;
+ unsigned long mask = BIT_MASK(nr);
+
+ p += BIT_WORD(nr);
+ if (READ_ONCE(*p) & mask)
+ return 1;
+
+ old = atomic_long_fetch_or_acquire(mask, (atomic_long_t *)p);
+ return !!(old & mask);
+}
+
/**
* clear_bit_unlock - Clear a bit in memory, for unlock
@@ -20,11 +37,11 @@
*
* This operation is atomic and provides release barrier semantics.
*/
-#define clear_bit_unlock(nr, addr) \
-do { \
- smp_mb__before_atomic(); \
- clear_bit(nr, addr); \
-} while (0)
+static inline void clear_bit_unlock(unsigned int nr, volatile unsigned long *p)
+{
+ p += BIT_WORD(nr);
+ atomic_long_fetch_andnot_release(BIT_MASK(nr), (atomic_long_t *)p);
+}
/**
* __clear_bit_unlock - Clear a bit in memory, for unlock
@@ -37,11 +54,38 @@ do { \
*
* See for example x86's implementation.
*/
-#define __clear_bit_unlock(nr, addr) \
-do { \
- smp_mb__before_atomic(); \
- clear_bit(nr, addr); \
-} while (0)
+static inline void __clear_bit_unlock(unsigned int nr,
+ volatile unsigned long *p)
+{
+ unsigned long old;
-#endif /* _ASM_GENERIC_BITOPS_LOCK_H_ */
+ p += BIT_WORD(nr);
+ old = READ_ONCE(*p);
+ old &= ~BIT_MASK(nr);
+ atomic_long_set_release((atomic_long_t *)p, old);
+}
+
+/**
+ * clear_bit_unlock_is_negative_byte - Clear a bit in memory and test if bottom
+ * byte is negative, for unlock.
+ * @nr: the bit to clear
+ * @addr: the address to start counting from
+ *
+ * This is a bit of a one-trick-pony for the filemap code, which clears
+ * PG_locked and tests PG_waiters,
+ */
+#ifndef clear_bit_unlock_is_negative_byte
+static inline bool clear_bit_unlock_is_negative_byte(unsigned int nr,
+ volatile unsigned long *p)
+{
+ long old;
+ unsigned long mask = BIT_MASK(nr);
+
+ p += BIT_WORD(nr);
+ old = atomic_long_fetch_andnot_release(mask, (atomic_long_t *)p);
+ return !!(old & BIT(7));
+}
+#define clear_bit_unlock_is_negative_byte clear_bit_unlock_is_negative_byte
+#endif
+#endif /* _ASM_GENERIC_BITOPS_LOCK_H_ */