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[PATCH] unify x86/x86-64 semaphore code

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This patch moves the common code in x86 and x86-64's semaphore.c into a
single file in lib/semaphore-sleepers.c.  The arch specific asm stubs are
left in the arch tree (in semaphore.c for i386 and in the asm for x86-64).
There should be no changes in code/functionality with this patch.

Signed-off-by: Benjamin LaHaise <benjamin.c.lahaise@intel.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Benjamin LaHaise 2005-09-03 15:56:52 -07:00 committed by Linus Torvalds
parent 4ad8d38342
commit 52fdd08903
9 changed files with 26 additions and 175 deletions
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4
arch/i386/Kconfig
View File

@ -14,6 +14,10 @@ config X86
486, 586, Pentiums, and various instruction-set-compatible chips by
AMD, Cyrix, and others.
config SEMAPHORE_SLEEPERS
bool
default y
config MMU
bool
default y

162
arch/i386/kernel/semaphore.c
View File

@ -13,170 +13,8 @@
* rw semaphores implemented November 1999 by Benjamin LaHaise <bcrl@kvack.org>
*/
#include <linux/config.h>
#include <linux/sched.h>
#include <linux/err.h>
#include <linux/init.h>
#include <asm/semaphore.h>
/*
* Semaphores are implemented using a two-way counter:
* The "count" variable is decremented for each process
* that tries to acquire the semaphore, while the "sleeping"
* variable is a count of such acquires.
*
* Notably, the inline "up()" and "down()" functions can
* efficiently test if they need to do any extra work (up
* needs to do something only if count was negative before
* the increment operation.
*
* "sleeping" and the contention routine ordering is protected
* by the spinlock in the semaphore's waitqueue head.
*
* Note that these functions are only called when there is
* contention on the lock, and as such all this is the
* "non-critical" part of the whole semaphore business. The
* critical part is the inline stuff in <asm/semaphore.h>
* where we want to avoid any extra jumps and calls.
*/
/*
* Logic:
* - only on a boundary condition do we need to care. When we go
* from a negative count to a non-negative, we wake people up.
* - when we go from a non-negative count to a negative do we
* (a) synchronize with the "sleeper" count and (b) make sure
* that we're on the wakeup list before we synchronize so that
* we cannot lose wakeup events.
*/
static fastcall void __attribute_used__ __up(struct semaphore *sem)
{
wake_up(&sem->wait);
}
static fastcall void __attribute_used__ __sched __down(struct semaphore * sem)
{
struct task_struct *tsk = current;
DECLARE_WAITQUEUE(wait, tsk);
unsigned long flags;
tsk->state = TASK_UNINTERRUPTIBLE;
spin_lock_irqsave(&sem->wait.lock, flags);
add_wait_queue_exclusive_locked(&sem->wait, &wait);
sem->sleepers++;
for (;;) {
int sleepers = sem->sleepers;
/*
* Add "everybody else" into it. They aren't
* playing, because we own the spinlock in
* the wait_queue_head.
*/
if (!atomic_add_negative(sleepers - 1, &sem->count)) {
sem->sleepers = 0;
break;
}
sem->sleepers = 1; /* us - see -1 above */
spin_unlock_irqrestore(&sem->wait.lock, flags);
schedule();
spin_lock_irqsave(&sem->wait.lock, flags);
tsk->state = TASK_UNINTERRUPTIBLE;
}
remove_wait_queue_locked(&sem->wait, &wait);
wake_up_locked(&sem->wait);
spin_unlock_irqrestore(&sem->wait.lock, flags);
tsk->state = TASK_RUNNING;
}
static fastcall int __attribute_used__ __sched __down_interruptible(struct semaphore * sem)
{
int retval = 0;
struct task_struct *tsk = current;
DECLARE_WAITQUEUE(wait, tsk);
unsigned long flags;
tsk->state = TASK_INTERRUPTIBLE;
spin_lock_irqsave(&sem->wait.lock, flags);
add_wait_queue_exclusive_locked(&sem->wait, &wait);
sem->sleepers++;
for (;;) {
int sleepers = sem->sleepers;
/*
* With signals pending, this turns into
* the trylock failure case - we won't be
* sleeping, and we* can't get the lock as
* it has contention. Just correct the count
* and exit.
*/
if (signal_pending(current)) {
retval = -EINTR;
sem->sleepers = 0;
atomic_add(sleepers, &sem->count);
break;
}
/*
* Add "everybody else" into it. They aren't
* playing, because we own the spinlock in
* wait_queue_head. The "-1" is because we're
* still hoping to get the semaphore.
*/
if (!atomic_add_negative(sleepers - 1, &sem->count)) {
sem->sleepers = 0;
break;
}
sem->sleepers = 1; /* us - see -1 above */
spin_unlock_irqrestore(&sem->wait.lock, flags);
schedule();
spin_lock_irqsave(&sem->wait.lock, flags);
tsk->state = TASK_INTERRUPTIBLE;
}
remove_wait_queue_locked(&sem->wait, &wait);
wake_up_locked(&sem->wait);
spin_unlock_irqrestore(&sem->wait.lock, flags);
tsk->state = TASK_RUNNING;
return retval;
}
/*
* Trylock failed - make sure we correct for
* having decremented the count.
*
* We could have done the trylock with a
* single "cmpxchg" without failure cases,
* but then it wouldn't work on a 386.
*/
static fastcall int __attribute_used__ __down_trylock(struct semaphore * sem)
{
int sleepers;
unsigned long flags;
spin_lock_irqsave(&sem->wait.lock, flags);
sleepers = sem->sleepers + 1;
sem->sleepers = 0;
/*
* Add "everybody else" and us into it. They aren't
* playing, because we own the spinlock in the
* wait_queue_head.
*/
if (!atomic_add_negative(sleepers, &sem->count)) {
wake_up_locked(&sem->wait);
}
spin_unlock_irqrestore(&sem->wait.lock, flags);
return 1;
}
/*
* The semaphore operations have a special calling sequence that
* allow us to do a simpler in-line version of them. These routines

4
arch/um/Kconfig_i386
View File

@ -6,6 +6,10 @@ config 64BIT
bool
default n
config SEMAPHORE_SLEEPERS
bool
default y
config TOP_ADDR
hex
default 0xc0000000 if !HOST_2G_2G

4
arch/um/Kconfig_x86_64
View File

@ -6,6 +6,10 @@ config 64BIT
bool
default y
config SEMAPHORE_SLEEPERS
bool
default y
config TOP_ADDR
hex
default 0x80000000

5
arch/um/sys-x86_64/Makefile
View File

@ -6,7 +6,7 @@
#XXX: why into lib-y?
lib-y = bitops.o bugs.o csum-partial.o delay.o fault.o mem.o memcpy.o \
ptrace.o ptrace_user.o semaphore.o sigcontext.o signal.o stub.o \
ptrace.o ptrace_user.o sigcontext.o signal.o stub.o \
stub_segv.o syscalls.o syscall_table.o sysrq.o thunk.o
obj-y := ksyms.o
@ -15,7 +15,7 @@ obj-$(CONFIG_MODULES) += module.o um_module.o
USER_OBJS := ptrace_user.o sigcontext.o
SYMLINKS = bitops.c csum-copy.S csum-partial.c csum-wrappers.c memcpy.S \
semaphore.c thunk.S module.c
thunk.S module.c
include arch/um/scripts/Makefile.rules
@ -24,7 +24,6 @@ csum-copy.S-dir = lib
csum-partial.c-dir = lib
csum-wrappers.c-dir = lib
memcpy.S-dir = lib
semaphore.c-dir = kernel
thunk.S-dir = lib
module.c-dir = kernel

4
arch/x86_64/Kconfig
View File

@ -24,6 +24,10 @@ config X86
bool
default y
config SEMAPHORE_SLEEPERS
bool
default y
config MMU
bool
default y

2
arch/x86_64/kernel/Makefile
View File

@ -4,7 +4,7 @@
extra-y := head.o head64.o init_task.o vmlinux.lds
EXTRA_AFLAGS := -traditional
obj-y := process.o semaphore.o signal.o entry.o traps.o irq.o \
obj-y := process.o signal.o entry.o traps.o irq.o \
ptrace.o time.o ioport.o ldt.o setup.o i8259.o sys_x86_64.o \
x8664_ksyms.o i387.o syscall.o vsyscall.o \
setup64.o bootflag.o e820.o reboot.o quirks.o

1
lib/Makefile
View File

@ -18,6 +18,7 @@ endif
lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
lib-$(CONFIG_SEMAPHORE_SLEEPERS) += semaphore-sleepers.o
lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o
obj-$(CONFIG_LOCK_KERNEL) += kernel_lock.o
obj-$(CONFIG_DEBUG_PREEMPT) += smp_processor_id.o

15
arch/x86_64/kernel/semaphore.c → lib/semaphore-sleepers.c
View File

@ -1,5 +1,5 @@
/*
* x86_64 semaphore implementation.
* i386 and x86-64 semaphore implementation.
*
* (C) Copyright 1999 Linus Torvalds
*
@ -14,9 +14,8 @@
*/
#include <linux/config.h>
#include <linux/sched.h>
#include <linux/err.h>
#include <linux/init.h>
#include <asm/errno.h>
#include <asm/semaphore.h>
/*
@ -50,12 +49,12 @@
* we cannot lose wakeup events.
*/
void __up(struct semaphore *sem)
fastcall void __up(struct semaphore *sem)
{
wake_up(&sem->wait);
}
void __sched __down(struct semaphore * sem)
fastcall void __sched __down(struct semaphore * sem)
{
struct task_struct *tsk = current;
DECLARE_WAITQUEUE(wait, tsk);
@ -92,7 +91,7 @@ void __sched __down(struct semaphore * sem)
tsk->state = TASK_RUNNING;
}
int __sched __down_interruptible(struct semaphore * sem)
fastcall int __sched __down_interruptible(struct semaphore * sem)
{
int retval = 0;
struct task_struct *tsk = current;
@ -155,7 +154,7 @@ int __sched __down_interruptible(struct semaphore * sem)
* single "cmpxchg" without failure cases,
* but then it wouldn't work on a 386.
*/
int __down_trylock(struct semaphore * sem)
fastcall int __down_trylock(struct semaphore * sem)
{
int sleepers;
unsigned long flags;
@ -176,5 +175,3 @@ int __down_trylock(struct semaphore * sem)
spin_unlock_irqrestore(&sem->wait.lock, flags);
return 1;
}