[PATCH v4 2/3] locking/rwsem: Remove rwsem-spinlock.c & use rwsem-xadd.c for all archs

Waiman Long
2019-02-13T22:00:16Z

Currently, we have two different implementation of rwsem:
1) CONFIG_RWSEM_GENERIC_SPINLOCK (rwsem-spinlock.c)
2) CONFIG_RWSEM_XCHGADD_ALGORITHM (rwsem-xadd.c)

As we are going to use a single generic implementation for rwsem-xadd.c
and no architecture-specific code will be needed, there is no point
in keeping two different implementations of rwsem. In most cases, the
performance of rwsem-spinlock.c will be worse. It also doesn't get all
the performance tuning and optimizations that had been implemented in
rwsem-xadd.c over the years.

For simplication, we are going to remove rwsem-spinlock.c and make all
architectures use a single implementation of rwsem - rwsem-xadd.c.

All references to RWSEM_GENERIC_SPINLOCK and RWSEM_XCHGADD_ALGORITHM
in the code are removed.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Waiman Long <longman@redhat.com>
---
arch/alpha/Kconfig | 7 -
arch/arc/Kconfig | 3 -
arch/arm/Kconfig | 4 -
arch/arm64/Kconfig | 3 -
arch/c6x/Kconfig | 3 -
arch/csky/Kconfig | 3 -
arch/h8300/Kconfig | 3 -
arch/hexagon/Kconfig | 6 -
arch/ia64/Kconfig | 4 -
arch/m68k/Kconfig | 7 -
arch/microblaze/Kconfig | 6 -
arch/mips/Kconfig | 7 -
arch/nds32/Kconfig | 3 -
arch/nios2/Kconfig | 3 -
arch/openrisc/Kconfig | 6 -
arch/parisc/Kconfig | 6 -
arch/powerpc/Kconfig | 7 -
arch/riscv/Kconfig | 3 -
arch/s390/Kconfig | 6 -
arch/sh/Kconfig | 6 -
arch/sparc/Kconfig | 8 -
arch/unicore32/Kconfig | 6 -
arch/x86/Kconfig | 3 -
arch/x86/um/Kconfig | 6 -
arch/xtensa/Kconfig | 3 -
include/linux/rwsem-spinlock.h | 47 ------
include/linux/rwsem.h | 5 -
kernel/Kconfig.locks | 2 +-
kernel/locking/Makefile | 4 +-
kernel/locking/rwsem-spinlock.c | 339 ----------------------------------------
kernel/locking/rwsem.h | 3 -
31 files changed, 2 insertions(+), 520 deletions(-)
delete mode 100644 include/linux/rwsem-spinlock.h
delete mode 100644 kernel/locking/rwsem-spinlock.c

diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 584a6e1..27c8712 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -49,13 +49,6 @@ config MMU
bool
default y

-config RWSEM_GENERIC_SPINLOCK
- bool
-
-config RWSEM_XCHGADD_ALGORITHM
- bool
- default y
-
config ARCH_HAS_ILOG2_U32
bool
default n
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 376366a..c0dd229 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -63,9 +63,6 @@ config SCHED_OMIT_FRAME_POINTER
config GENERIC_CSUM
def_bool y

-config RWSEM_GENERIC_SPINLOCK
- def_bool y
-
config ARCH_DISCONTIGMEM_ENABLE
def_bool n

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 664e918..4d81f69 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -176,10 +176,6 @@ config TRACE_IRQFLAGS_SUPPORT
bool
default !CPU_V7M

-config RWSEM_XCHGADD_ALGORITHM
- bool
- default y
-
config ARCH_HAS_ILOG2_U32
bool

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index a4168d3..24bbcfa 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -238,9 +238,6 @@ config LOCKDEP_SUPPORT
config TRACE_IRQFLAGS_SUPPORT
def_bool y

-config RWSEM_XCHGADD_ALGORITHM
- def_bool y
-
config GENERIC_BUG
def_bool y
depends on BUG
diff --git a/arch/c6x/Kconfig b/arch/c6x/Kconfig
index 456e154..f114655 100644
--- a/arch/c6x/Kconfig
+++ b/arch/c6x/Kconfig
@@ -26,9 +26,6 @@ config MMU
config FPU
def_bool n

-config RWSEM_GENERIC_SPINLOCK
- def_bool y
-
config GENERIC_CALIBRATE_DELAY
def_bool y

diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
index 398113c..90279a1 100644
--- a/arch/csky/Kconfig
+++ b/arch/csky/Kconfig
@@ -93,9 +93,6 @@ config GENERIC_HWEIGHT
config MMU
def_bool y

-config RWSEM_GENERIC_SPINLOCK
- def_bool y
-
config STACKTRACE_SUPPORT
def_bool y

diff --git a/arch/h8300/Kconfig b/arch/h8300/Kconfig
index 6472a06..ba33326 100644
--- a/arch/h8300/Kconfig
+++ b/arch/h8300/Kconfig
@@ -26,9 +26,6 @@ config H8300
config CPU_BIG_ENDIAN
def_bool y

-config RWSEM_GENERIC_SPINLOCK
- def_bool y
-
config GENERIC_HWEIGHT
def_bool y

diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig
index fb2fbfc..5d07c8d 100644
--- a/arch/hexagon/Kconfig
+++ b/arch/hexagon/Kconfig
@@ -64,12 +64,6 @@ config GENERIC_CSUM
config GENERIC_IRQ_PROBE
def_bool y

-config RWSEM_GENERIC_SPINLOCK
- def_bool n
-
-config RWSEM_XCHGADD_ALGORITHM
- def_bool y
-
config GENERIC_HWEIGHT
def_bool y

diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 8d7396b..73a26f0 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -83,10 +83,6 @@ config STACKTRACE_SUPPORT
config GENERIC_LOCKBREAK
def_bool n

-config RWSEM_XCHGADD_ALGORITHM
- bool
- default y
-
config HUGETLB_PAGE_SIZE_VARIABLE
bool
depends on HUGETLB_PAGE
diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index e173ea2..6ace0b2 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -31,13 +31,6 @@ config M68K
config CPU_BIG_ENDIAN
def_bool y

-config RWSEM_GENERIC_SPINLOCK
- bool
- default y
-
-config RWSEM_XCHGADD_ALGORITHM
- bool
-
config ARCH_HAS_ILOG2_U32
bool

diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
index 58aff26..d459c70 100644
--- a/arch/microblaze/Kconfig
+++ b/arch/microblaze/Kconfig
@@ -57,15 +57,9 @@ config CPU_LITTLE_ENDIAN

endchoice

-config RWSEM_GENERIC_SPINLOCK
- def_bool y
-
config ZONE_DMA
def_bool y

-config RWSEM_XCHGADD_ALGORITHM
- bool
-
config ARCH_HAS_ILOG2_U32
def_bool n

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index a84c24d..6ad1882 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1037,13 +1037,6 @@ source "arch/mips/paravirt/Kconfig"

endmenu

-config RWSEM_GENERIC_SPINLOCK
- bool
- default y
-
-config RWSEM_XCHGADD_ALGORITHM
- bool
-
config GENERIC_HWEIGHT
bool
default y
diff --git a/arch/nds32/Kconfig b/arch/nds32/Kconfig
index dda1906..6a3c53d 100644
--- a/arch/nds32/Kconfig
+++ b/arch/nds32/Kconfig
@@ -59,9 +59,6 @@ config GENERIC_LOCKBREAK
def_bool y
depends on PREEMPT

-config RWSEM_GENERIC_SPINLOCK
- def_bool y
-
config TRACE_IRQFLAGS_SUPPORT
def_bool y

diff --git a/arch/nios2/Kconfig b/arch/nios2/Kconfig
index 532343e..715e6c0 100644
--- a/arch/nios2/Kconfig
+++ b/arch/nios2/Kconfig
@@ -39,9 +39,6 @@ config NO_IOPORT_MAP
config FPU
def_bool n

-config RWSEM_GENERIC_SPINLOCK
- def_bool y
-
config TRACE_IRQFLAGS_SUPPORT
def_bool n

diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
index 09ab59e..9f51da5 100644
--- a/arch/openrisc/Kconfig
+++ b/arch/openrisc/Kconfig
@@ -42,12 +42,6 @@ config CPU_BIG_ENDIAN
config MMU
def_bool y

-config RWSEM_GENERIC_SPINLOCK
- def_bool y
-
-config RWSEM_XCHGADD_ALGORITHM
- def_bool n
-
config GENERIC_HWEIGHT
def_bool y

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 7ca2c3e..8efbeea 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -74,12 +74,6 @@ config GENERIC_LOCKBREAK
default y
depends on SMP && PREEMPT

-config RWSEM_GENERIC_SPINLOCK
- def_bool y
-
-config RWSEM_XCHGADD_ALGORITHM
- bool
-
config ARCH_HAS_ILOG2_U32
bool
default n
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 2890d36..466e90f 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -103,13 +103,6 @@ config LOCKDEP_SUPPORT
bool
default y

-config RWSEM_GENERIC_SPINLOCK
- bool
-
-config RWSEM_XCHGADD_ALGORITHM
- bool
- default y
-
config GENERIC_LOCKBREAK
bool
default y
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 515fc3c..2b34482 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -69,9 +69,6 @@ config STACKTRACE_SUPPORT
config TRACE_IRQFLAGS_SUPPORT
def_bool y

-config RWSEM_GENERIC_SPINLOCK
- def_bool y
-
config GENERIC_BUG
def_bool y
depends on BUG
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index ed554b0..0ec9d8e 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -14,12 +14,6 @@ config LOCKDEP_SUPPORT
config STACKTRACE_SUPPORT
def_bool y

-config RWSEM_GENERIC_SPINLOCK
- bool
-
-config RWSEM_XCHGADD_ALGORITHM
- def_bool y
-
config ARCH_HAS_ILOG2_U32
def_bool n

diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index a9c36f9..4f8c747 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -89,12 +89,6 @@ config ARCH_DEFCONFIG
default "arch/sh/configs/shx3_defconfig" if SUPERH32
default "arch/sh/configs/cayman_defconfig" if SUPERH64

-config RWSEM_GENERIC_SPINLOCK
- def_bool y
-
-config RWSEM_XCHGADD_ALGORITHM
- bool
-
config GENERIC_BUG
def_bool y
depends on BUG && SUPERH32
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index d5dd652..6d0036a 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -190,14 +190,6 @@ config NR_CPUS

source "kernel/Kconfig.hz"

-config RWSEM_GENERIC_SPINLOCK
- bool
- default y if SPARC32
-
-config RWSEM_XCHGADD_ALGORITHM
- bool
- default y if SPARC64
-
config GENERIC_HWEIGHT
bool
default y
diff --git a/arch/unicore32/Kconfig b/arch/unicore32/Kconfig
index c3a41bf..e080087 100644
--- a/arch/unicore32/Kconfig
+++ b/arch/unicore32/Kconfig
@@ -38,12 +38,6 @@ config STACKTRACE_SUPPORT
config LOCKDEP_SUPPORT
def_bool y

-config RWSEM_GENERIC_SPINLOCK
- def_bool y
-
-config RWSEM_XCHGADD_ALGORITHM
- bool
-
config ARCH_HAS_ILOG2_U32
bool

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 6826143..be6cc2c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -269,9 +269,6 @@ config ARCH_MAY_HAVE_PC_FDC
def_bool y
depends on ISA_DMA_API

-config RWSEM_XCHGADD_ALGORITHM
- def_bool y
-
config GENERIC_CALIBRATE_DELAY
def_bool y

diff --git a/arch/x86/um/Kconfig b/arch/x86/um/Kconfig
index f518b47..4dc3217 100644
--- a/arch/x86/um/Kconfig
+++ b/arch/x86/um/Kconfig
@@ -32,12 +32,6 @@ config ARCH_DEFCONFIG
default "arch/um/configs/i386_defconfig" if X86_32
default "arch/um/configs/x86_64_defconfig" if X86_64

-config RWSEM_XCHGADD_ALGORITHM
- def_bool 64BIT
-
-config RWSEM_GENERIC_SPINLOCK
- def_bool !RWSEM_XCHGADD_ALGORITHM
-
config 3_LEVEL_PGTABLES
bool "Three-level pagetables" if !64BIT
default 64BIT
diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index ce91682..4f0a903 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -43,9 +43,6 @@ config XTENSA
with reasonable minimum requirements. The Xtensa Linux project has
a home page at <http://www.linux-xtensa.org/>.

-config RWSEM_XCHGADD_ALGORITHM
- def_bool y
-
config GENERIC_HWEIGHT
def_bool y

diff --git a/include/linux/rwsem-spinlock.h b/include/linux/rwsem-spinlock.h
deleted file mode 100644
index e475683..0000000
--- a/include/linux/rwsem-spinlock.h
+++ /dev/null
@@ -1,47 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/* rwsem-spinlock.h: fallback C implementation
- *
- * Copyright (c) 2001 David Howells (dhowells@redhat.com).
- * - Derived partially from ideas by Andrea Arcangeli <andrea@suse.de>
- * - Derived also from comments by Linus
- */
-
-#ifndef _LINUX_RWSEM_SPINLOCK_H
-#define _LINUX_RWSEM_SPINLOCK_H
-
-#ifndef _LINUX_RWSEM_H
-#error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead"
-#endif
-
-#ifdef __KERNEL__
-/*
- * the rw-semaphore definition
- * - if count is 0 then there are no active readers or writers
- * - if count is +ve then that is the number of active readers
- * - if count is -1 then there is one active writer
- * - if wait_list is not empty, then there are processes waiting for the semaphore
- */
-struct rw_semaphore {
- __s32 count;
- raw_spinlock_t wait_lock;
- struct list_head wait_list;
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
- struct lockdep_map dep_map;
-#endif
-};
-
-#define RWSEM_UNLOCKED_VALUE 0x00000000
-
-extern void __down_read(struct rw_semaphore *sem);
-extern int __must_check __down_read_killable(struct rw_semaphore *sem);
-extern int __down_read_trylock(struct rw_semaphore *sem);
-extern void __down_write(struct rw_semaphore *sem);
-extern int __must_check __down_write_killable(struct rw_semaphore *sem);
-extern int __down_write_trylock(struct rw_semaphore *sem);
-extern void __up_read(struct rw_semaphore *sem);
-extern void __up_write(struct rw_semaphore *sem);
-extern void __downgrade_write(struct rw_semaphore *sem);
-extern int rwsem_is_locked(struct rw_semaphore *sem);
-
-#endif /* __KERNEL__ */
-#endif /* _LINUX_RWSEM_SPINLOCK_H */
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 6e56006..0fc4106 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -22,10 +22,6 @@

struct rw_semaphore;

-#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
-#include <linux/rwsem-spinlock.h> /* use a generic implementation */
-#define __RWSEM_INIT_COUNT(name) .count = RWSEM_UNLOCKED_VALUE
-#else
/* All arch specific implementations share the same struct */
struct rw_semaphore {
atomic_long_t count;
@@ -65,7 +61,6 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)

#define RWSEM_UNLOCKED_VALUE 0L
#define __RWSEM_INIT_COUNT(name) .count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE)
-#endif

/* Common initializer macros and functions */

diff --git a/kernel/Kconfig.locks b/kernel/Kconfig.locks
index 84d882f..74775ed 100644
--- a/kernel/Kconfig.locks
+++ b/kernel/Kconfig.locks
@@ -229,7 +229,7 @@ config MUTEX_SPIN_ON_OWNER

config RWSEM_SPIN_ON_OWNER
def_bool y
- depends on SMP && RWSEM_XCHGADD_ALGORITHM && ARCH_SUPPORTS_ATOMIC_RMW
+ depends on SMP && ARCH_SUPPORTS_ATOMIC_RMW

config LOCK_SPIN_ON_OWNER
def_bool y
diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile
index 392c7f2..1af83e9 100644
--- a/kernel/locking/Makefile
+++ b/kernel/locking/Makefile
@@ -3,7 +3,7 @@
# and is generally not a function of system call inputs.
KCOV_INSTRUMENT := n

-obj-y += mutex.o semaphore.o rwsem.o percpu-rwsem.o
+obj-y += mutex.o semaphore.o rwsem.o percpu-rwsem.o rwsem-xadd.o

ifdef CONFIG_FUNCTION_TRACER
CFLAGS_REMOVE_lockdep.o = $(CC_FLAGS_FTRACE)
@@ -25,8 +25,6 @@ obj-$(CONFIG_RT_MUTEXES) += rtmutex.o
obj-$(CONFIG_DEBUG_RT_MUTEXES) += rtmutex-debug.o
obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock_debug.o
-obj-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
-obj-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem-xadd.o
obj-$(CONFIG_QUEUED_RWLOCKS) += qrwlock.o
obj-$(CONFIG_LOCK_TORTURE_TEST) += locktorture.o
obj-$(CONFIG_WW_MUTEX_SELFTEST) += test-ww_mutex.o
diff --git a/kernel/locking/rwsem-spinlock.c b/kernel/locking/rwsem-spinlock.c
deleted file mode 100644
index a7ffb2a..0000000
--- a/kernel/locking/rwsem-spinlock.c
+++ /dev/null
@@ -1,339 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/* rwsem-spinlock.c: R/W semaphores: contention handling functions for
- * generic spinlock implementation
- *
- * Copyright (c) 2001 David Howells (dhowells@redhat.com).
- * - Derived partially from idea by Andrea Arcangeli <andrea@suse.de>
- * - Derived also from comments by Linus
- */
-#include <linux/rwsem.h>
-#include <linux/sched/signal.h>
-#include <linux/sched/debug.h>
-#include <linux/export.h>
-
-enum rwsem_waiter_type {
- RWSEM_WAITING_FOR_WRITE,
- RWSEM_WAITING_FOR_READ
-};
-
-struct rwsem_waiter {
- struct list_head list;
- struct task_struct *task;
- enum rwsem_waiter_type type;
-};
-
-int rwsem_is_locked(struct rw_semaphore *sem)
-{
- int ret = 1;
- unsigned long flags;
-
- if (raw_spin_trylock_irqsave(&sem->wait_lock, flags)) {
- ret = (sem->count != 0);
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
- }
- return ret;
-}
-EXPORT_SYMBOL(rwsem_is_locked);
-
-/*
- * initialise the semaphore
- */
-void __init_rwsem(struct rw_semaphore *sem, const char *name,
- struct lock_class_key *key)
-{
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
- /*
- * Make sure we are not reinitializing a held semaphore:
- */
- debug_check_no_locks_freed((void *)sem, sizeof(*sem));
- lockdep_init_map(&sem->dep_map, name, key, 0);
-#endif
- sem->count = 0;
- raw_spin_lock_init(&sem->wait_lock);
- INIT_LIST_HEAD(&sem->wait_list);
-}
-EXPORT_SYMBOL(__init_rwsem);
-
-/*
- * handle the lock release when processes blocked on it that can now run
- * - if we come here, then:
- * - the 'active count' _reached_ zero
- * - the 'waiting count' is non-zero
- * - the spinlock must be held by the caller
- * - woken process blocks are discarded from the list after having task zeroed
- * - writers are only woken if wakewrite is non-zero
- */
-static inline struct rw_semaphore *
-__rwsem_do_wake(struct rw_semaphore *sem, int wakewrite)
-{
- struct rwsem_waiter *waiter;
- struct task_struct *tsk;
- int woken;
-
- waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
-
- if (waiter->type == RWSEM_WAITING_FOR_WRITE) {
- if (wakewrite)
- /* Wake up a writer. Note that we do not grant it the
- * lock - it will have to acquire it when it runs. */
- wake_up_process(waiter->task);
- goto out;
- }
-
- /* grant an infinite number of read locks to the front of the queue */
- woken = 0;
- do {
- struct list_head *next = waiter->list.next;
-
- list_del(&waiter->list);
- tsk = waiter->task;
- /*
- * Make sure we do not wakeup the next reader before
- * setting the nil condition to grant the next reader;
- * otherwise we could miss the wakeup on the other
- * side and end up sleeping again. See the pairing
- * in rwsem_down_read_failed().
- */
- smp_mb();
- waiter->task = NULL;
- wake_up_process(tsk);
- put_task_struct(tsk);
- woken++;
- if (next == &sem->wait_list)
- break;
- waiter = list_entry(next, struct rwsem_waiter, list);
- } while (waiter->type != RWSEM_WAITING_FOR_WRITE);
-
- sem->count += woken;
-
- out:
- return sem;
-}
-
-/*
- * wake a single writer
- */
-static inline struct rw_semaphore *
-__rwsem_wake_one_writer(struct rw_semaphore *sem)
-{
- struct rwsem_waiter *waiter;
-
- waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
- wake_up_process(waiter->task);
-
- return sem;
-}
-
-/*
- * get a read lock on the semaphore
- */
-int __sched __down_read_common(struct rw_semaphore *sem, int state)
-{
- struct rwsem_waiter waiter;
- unsigned long flags;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- if (sem->count >= 0 && list_empty(&sem->wait_list)) {
- /* granted */
- sem->count++;
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
- goto out;
- }
-
- /* set up my own style of waitqueue */
- waiter.task = current;
- waiter.type = RWSEM_WAITING_FOR_READ;
- get_task_struct(current);
-
- list_add_tail(&waiter.list, &sem->wait_list);
-
- /* wait to be given the lock */
- for (;;) {
- if (!waiter.task)
- break;
- if (signal_pending_state(state, current))
- goto out_nolock;
- set_current_state(state);
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
- schedule();
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
- }
-
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
- out:
- return 0;
-
-out_nolock:
- /*
- * We didn't take the lock, so that there is a writer, which
- * is owner or the first waiter of the sem. If it's a waiter,
- * it will be woken by current owner. Not need to wake anybody.
- */
- list_del(&waiter.list);
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
- return -EINTR;
-}
-
-void __sched __down_read(struct rw_semaphore *sem)
-{
- __down_read_common(sem, TASK_UNINTERRUPTIBLE);
-}
-
-int __sched __down_read_killable(struct rw_semaphore *sem)
-{
- return __down_read_common(sem, TASK_KILLABLE);
-}
-
-/*
- * trylock for reading -- returns 1 if successful, 0 if contention
- */
-int __down_read_trylock(struct rw_semaphore *sem)
-{
- unsigned long flags;
- int ret = 0;
-
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- if (sem->count >= 0 && list_empty(&sem->wait_list)) {
- /* granted */
- sem->count++;
- ret = 1;
- }
-
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
-
- return ret;
-}
-
-/*
- * get a write lock on the semaphore
- */
-int __sched __down_write_common(struct rw_semaphore *sem, int state)
-{
- struct rwsem_waiter waiter;
- unsigned long flags;
- int ret = 0;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- /* set up my own style of waitqueue */
- waiter.task = current;
- waiter.type = RWSEM_WAITING_FOR_WRITE;
- list_add_tail(&waiter.list, &sem->wait_list);
-
- /* wait for someone to release the lock */
- for (;;) {
- /*
- * That is the key to support write lock stealing: allows the
- * task already on CPU to get the lock soon rather than put
- * itself into sleep and waiting for system woke it or someone
- * else in the head of the wait list up.
- */
- if (sem->count == 0)
- break;
- if (signal_pending_state(state, current))
- goto out_nolock;
-
- set_current_state(state);
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
- schedule();
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
- }
- /* got the lock */
- sem->count = -1;
- list_del(&waiter.list);
-
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
-
- return ret;
-
-out_nolock:
- list_del(&waiter.list);
- if (!list_empty(&sem->wait_list) && sem->count >= 0)
- __rwsem_do_wake(sem, 0);
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
-
- return -EINTR;
-}
-
-void __sched __down_write(struct rw_semaphore *sem)
-{
- __down_write_common(sem, TASK_UNINTERRUPTIBLE);
-}
-
-int __sched __down_write_killable(struct rw_semaphore *sem)
-{
- return __down_write_common(sem, TASK_KILLABLE);
-}
-
-/*
- * trylock for writing -- returns 1 if successful, 0 if contention
- */
-int __down_write_trylock(struct rw_semaphore *sem)
-{
- unsigned long flags;
- int ret = 0;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- if (sem->count == 0) {
- /* got the lock */
- sem->count = -1;
- ret = 1;
- }
-
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
-
- return ret;
-}
-
-/*
- * release a read lock on the semaphore
- */
-void __up_read(struct rw_semaphore *sem)
-{
- unsigned long flags;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- if (--sem->count == 0 && !list_empty(&sem->wait_list))
- sem = __rwsem_wake_one_writer(sem);
-
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
-}
-
-/*
- * release a write lock on the semaphore
- */
-void __up_write(struct rw_semaphore *sem)
-{
- unsigned long flags;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- sem->count = 0;
- if (!list_empty(&sem->wait_list))
- sem = __rwsem_do_wake(sem, 1);
-
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
-}
-
-/*
- * downgrade a write lock into a read lock
- * - just wake up any readers at the front of the queue
- */
-void __downgrade_write(struct rw_semaphore *sem)
-{
- unsigned long flags;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- sem->count = 1;
- if (!list_empty(&sem->wait_list))
- sem = __rwsem_do_wake(sem, 0);
-
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
-}
-
diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h
index 067e265..45ee002 100644
--- a/kernel/locking/rwsem.h
+++ b/kernel/locking/rwsem.h
@@ -153,7 +153,6 @@ static inline void rwsem_clear_reader_owned(struct rw_semaphore *sem)
}
#endif

-#ifdef CONFIG_RWSEM_XCHGADD_ALGORITHM
/*
* lock for reading
*/
@@ -260,5 +259,3 @@ static inline void __downgrade_write(struct rw_semaphore *sem)
if (tmp < 0)
rwsem_downgrade_wake(sem);
}
-
-#endif /* CONFIG_RWSEM_XCHGADD_ALGORITHM */
--
1.8.3.1