Commit 26333576 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

bitops: introduce lock ops



Introduce test_and_set_bit_lock / clear_bit_unlock bitops with lock semantics.
Convert all architectures to use the generic implementation.
Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Acked-By: default avatarDavid Howells <dhowells@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Bryan Wu <bryan.wu@analog.com>
Cc: Mikael Starvik <starvik@axis.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Greg Ungerer <gerg@uclinux.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Matthew Wilcox <willy@debian.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Kazumoto Kojima <kkojima@rr.iij4u.or.jp>
Cc: Richard Curnow <rc@rc0.org.uk>
Cc: William Lee Irwin III <wli@holomorphy.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Miles Bader <uclinux-v850@lsi.nec.co.jp>
Cc: Andi Kleen <ak@muc.de>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 38048983
......@@ -418,6 +418,20 @@ brothers:
*/
smp_mb__after_clear_bit();
There are two special bitops with lock barrier semantics (acquire/release,
same as spinlocks). These operate in the same way as their non-_lock/unlock
postfixed variants, except that they are to provide acquire/release semantics,
respectively. This means they can be used for bit_spin_trylock and
bit_spin_unlock type operations without specifying any more barriers.
int test_and_set_bit_lock(unsigned long nr, unsigned long *addr);
void clear_bit_unlock(unsigned long nr, unsigned long *addr);
void __clear_bit_unlock(unsigned long nr, unsigned long *addr);
The __clear_bit_unlock version is non-atomic, however it still implements
unlock barrier semantics. This can be useful if the lock itself is protecting
the other bits in the word.
Finally, there are non-atomic versions of the bitmask operations
provided. They are used in contexts where some other higher-level SMP
locking scheme is being used to protect the bitmask, and thus less
......
......@@ -1479,7 +1479,8 @@ kernel.
Any atomic operation that modifies some state in memory and returns information
about the state (old or new) implies an SMP-conditional general memory barrier
(smp_mb()) on each side of the actual operation. These include:
(smp_mb()) on each side of the actual operation (with the exception of
explicit lock operations, described later). These include:
xchg();
cmpxchg();
......@@ -1536,10 +1537,19 @@ If they're used for constructing a lock of some description, then they probably
do need memory barriers as a lock primitive generally has to do things in a
specific order.
Basically, each usage case has to be carefully considered as to whether memory
barriers are needed or not.
The following operations are special locking primitives:
test_and_set_bit_lock();
clear_bit_unlock();
__clear_bit_unlock();
These implement LOCK-class and UNLOCK-class operations. These should be used in
preference to other operations when implementing locking primitives, because
their implementations can be optimised on many architectures.
[!] Note that special memory barrier primitives are available for these
situations because on some CPUs the atomic instructions used imply full memory
barriers, and so barrier instructions are superfluous in conjunction with them,
......
......@@ -367,6 +367,7 @@ static inline unsigned int hweight8(unsigned int w)
#else
#include <asm-generic/bitops/hweight.h>
#endif
#include <asm-generic/bitops/lock.h>
#endif /* __KERNEL__ */
......
......@@ -286,6 +286,7 @@ static inline int constant_fls(int x)
#include <asm-generic/bitops/sched.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
/*
* Ext2 is defined to use little-endian byte ordering.
......
......@@ -288,6 +288,7 @@ static inline int ffs(unsigned long word)
#include <asm-generic/bitops/fls64.h>
#include <asm-generic/bitops/sched.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
#include <asm-generic/bitops/ext2-non-atomic.h>
#include <asm-generic/bitops/ext2-atomic.h>
......
......@@ -199,6 +199,7 @@ static __inline__ int __test_bit(int nr, const void *addr)
#include <asm-generic/bitops/find.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
#include <asm-generic/bitops/ext2-atomic.h>
#include <asm-generic/bitops/ext2-non-atomic.h>
......
......@@ -154,6 +154,7 @@ static inline int test_and_change_bit(int nr, volatile unsigned long *addr)
#include <asm-generic/bitops/fls64.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/find.h>
#include <asm-generic/bitops/lock.h>
#include <asm-generic/bitops/ext2-non-atomic.h>
......
......@@ -302,6 +302,7 @@ int __ilog2_u64(u64 n)
#include <asm-generic/bitops/sched.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
#include <asm-generic/bitops/ext2-non-atomic.h>
......
......@@ -22,6 +22,7 @@
#include <asm-generic/bitops/sched.h>
#include <asm-generic/bitops/ffs.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
#include <asm-generic/bitops/ext2-non-atomic.h>
#include <asm-generic/bitops/ext2-atomic.h>
......
#ifndef _ASM_GENERIC_BITOPS_LOCK_H_
#define _ASM_GENERIC_BITOPS_LOCK_H_
/**
* test_and_set_bit_lock - Set a bit and return its old value, for lock
* @nr: Bit to set
* @addr: Address to count from
*
* This operation is atomic and provides acquire barrier semantics.
* It can be used to implement bit locks.
*/
#define test_and_set_bit_lock(nr, addr) test_and_set_bit(nr, addr)
/**
* clear_bit_unlock - Clear a bit in memory, for unlock
* @nr: the bit to set
* @addr: the address to start counting from
*
* This operation is atomic and provides release barrier semantics.
*/
#define clear_bit_unlock(nr, addr) \
do { \
smp_mb__before_clear_bit(); \
clear_bit(nr, addr); \
} while (0)
/**
* __clear_bit_unlock - Clear a bit in memory, for unlock
* @nr: the bit to set
* @addr: the address to start counting from
*
* This operation is like clear_bit_unlock, however it is not atomic.
* It does provide release barrier semantics so it can be used to unlock
* a bit lock, however it would only be used if no other CPU can modify
* any bits in the memory until the lock is released (a good example is
* if the bit lock itself protects access to the other bits in the word).
*/
#define __clear_bit_unlock(nr, addr) \
do { \
smp_mb(); \
__clear_bit(nr, addr); \
} while (0)
#endif /* _ASM_GENERIC_BITOPS_LOCK_H_ */
......@@ -194,6 +194,7 @@ static __inline__ unsigned long __ffs(unsigned long word)
#include <asm-generic/bitops/find.h>
#include <asm-generic/bitops/sched.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
#include <asm-generic/bitops/ext2-non-atomic.h>
#include <asm-generic/bitops/ext2-atomic.h>
#include <asm-generic/bitops/minix.h>
......
......@@ -371,6 +371,8 @@ hweight64 (unsigned long x)
#define hweight16(x) (unsigned int) hweight64((x) & 0xfffful)
#define hweight8(x) (unsigned int) hweight64((x) & 0xfful)
#include <asm-generic/bitops/lock.h>
#endif /* __KERNEL__ */
#include <asm-generic/bitops/find.h>
......
......@@ -255,6 +255,7 @@ static __inline__ int test_and_change_bit(int nr, volatile void * addr)
#include <asm-generic/bitops/find.h>
#include <asm-generic/bitops/ffs.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
#endif /* __KERNEL__ */
......
......@@ -314,6 +314,7 @@ static inline int fls(int x)
#include <asm-generic/bitops/fls64.h>
#include <asm-generic/bitops/sched.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
/* Bitmap functions for the minix filesystem */
......
......@@ -160,6 +160,7 @@ static __inline__ int __test_bit(int nr, const volatile unsigned long * addr)
#include <asm-generic/bitops/find.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
static __inline__ int ext2_set_bit(int nr, volatile void * addr)
{
......
......@@ -556,6 +556,7 @@ static inline int ffs(int word)
#include <asm-generic/bitops/sched.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
#include <asm-generic/bitops/ext2-non-atomic.h>
#include <asm-generic/bitops/ext2-atomic.h>
#include <asm-generic/bitops/minix.h>
......
......@@ -208,6 +208,7 @@ static __inline__ int fls(int x)
#include <asm-generic/bitops/fls64.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
#include <asm-generic/bitops/sched.h>
#endif /* __KERNEL__ */
......
......@@ -266,6 +266,7 @@ static __inline__ int fls(unsigned int x)
#include <asm-generic/bitops/fls64.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
#define find_first_zero_bit(addr, size) find_next_zero_bit((addr), (size), 0)
unsigned long find_next_zero_bit(const unsigned long *addr,
......
......@@ -746,6 +746,7 @@ static inline int sched_find_first_bit(unsigned long *b)
#include <asm-generic/bitops/fls64.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
/*
* ATTENTION: intel byte ordering convention for ext2 and minix !!
......
......@@ -137,6 +137,7 @@ static inline unsigned long __ffs(unsigned long word)
#include <asm-generic/bitops/find.h>
#include <asm-generic/bitops/ffs.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
#include <asm-generic/bitops/sched.h>
#include <asm-generic/bitops/ext2-non-atomic.h>
#include <asm-generic/bitops/ext2-atomic.h>
......
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