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authorMatthew Wilcox <matthew@wil.cx>2008-03-07 21:55:58 -0500
committerMatthew Wilcox <willy@linux.intel.com>2008-04-17 10:42:34 -0400
commit64ac24e738823161693bf791f87adc802cf529ff (patch)
tree19c0b0cf314d4394ca580c05b86cdf874ce0a167 /arch/xtensa/kernel
parente48b3deee475134585eed03e7afebe4bf9e0dba9 (diff)
Generic semaphore implementation
Semaphores are no longer performance-critical, so a generic C implementation is better for maintainability, debuggability and extensibility. Thanks to Peter Zijlstra for fixing the lockdep warning. Thanks to Harvey Harrison for pointing out that the unlikely() was unnecessary. Signed-off-by: Matthew Wilcox <willy@linux.intel.com> Acked-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/xtensa/kernel')
-rw-r--r--arch/xtensa/kernel/Makefile2
-rw-r--r--arch/xtensa/kernel/semaphore.c226
-rw-r--r--arch/xtensa/kernel/xtensa_ksyms.c9
3 files changed, 1 insertions, 236 deletions
diff --git a/arch/xtensa/kernel/Makefile b/arch/xtensa/kernel/Makefile
index f582d6a24ec2..7419dbccf027 100644
--- a/arch/xtensa/kernel/Makefile
+++ b/arch/xtensa/kernel/Makefile
@@ -5,7 +5,7 @@
extra-y := head.o vmlinux.lds
-obj-y := align.o entry.o irq.o coprocessor.o process.o ptrace.o semaphore.o \
+obj-y := align.o entry.o irq.o coprocessor.o process.o ptrace.o \
setup.o signal.o syscall.o time.o traps.o vectors.o platform.o \
pci-dma.o init_task.o io.o
diff --git a/arch/xtensa/kernel/semaphore.c b/arch/xtensa/kernel/semaphore.c
deleted file mode 100644
index 995c6410ae10..000000000000
--- a/arch/xtensa/kernel/semaphore.c
+++ /dev/null
@@ -1,226 +0,0 @@
-/*
- * arch/xtensa/kernel/semaphore.c
- *
- * Generic semaphore code. Buyer beware. Do your own specific changes
- * in <asm/semaphore-helper.h>
- *
- * This file is subject to the terms and conditions of the GNU General Public
- * License. See the file "COPYING" in the main directory of this archive
- * for more details.
- *
- * Copyright (C) 2001 - 2005 Tensilica Inc.
- *
- * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
- * Chris Zankel <chris@zankel.net>
- * Marc Gauthier<marc@tensilica.com, marc@alumni.uwaterloo.ca>
- * Kevin Chea
- */
-
-#include <linux/sched.h>
-#include <linux/wait.h>
-#include <linux/init.h>
-#include <asm/semaphore.h>
-#include <asm/errno.h>
-
-/*
- * These two _must_ execute atomically wrt each other.
- */
-
-static __inline__ void wake_one_more(struct semaphore * sem)
-{
- atomic_inc((atomic_t *)&sem->sleepers);
-}
-
-static __inline__ int waking_non_zero(struct semaphore *sem)
-{
- unsigned long flags;
- int ret = 0;
-
- spin_lock_irqsave(&semaphore_wake_lock, flags);
- if (sem->sleepers > 0) {
- sem->sleepers--;
- ret = 1;
- }
- spin_unlock_irqrestore(&semaphore_wake_lock, flags);
- return ret;
-}
-
-/*
- * waking_non_zero_interruptible:
- * 1 got the lock
- * 0 go to sleep
- * -EINTR interrupted
- *
- * We must undo the sem->count down_interruptible() increment while we are
- * protected by the spinlock in order to make atomic this atomic_inc() with the
- * atomic_read() in wake_one_more(), otherwise we can race. -arca
- */
-
-static __inline__ int waking_non_zero_interruptible(struct semaphore *sem,
- struct task_struct *tsk)
-{
- unsigned long flags;
- int ret = 0;
-
- spin_lock_irqsave(&semaphore_wake_lock, flags);
- if (sem->sleepers > 0) {
- sem->sleepers--;
- ret = 1;
- } else if (signal_pending(tsk)) {
- atomic_inc(&sem->count);
- ret = -EINTR;
- }
- spin_unlock_irqrestore(&semaphore_wake_lock, flags);
- return ret;
-}
-
-/*
- * waking_non_zero_trylock:
- * 1 failed to lock
- * 0 got the lock
- *
- * We must undo the sem->count down_trylock() increment while we are
- * protected by the spinlock in order to make atomic this atomic_inc() with the
- * atomic_read() in wake_one_more(), otherwise we can race. -arca
- */
-
-static __inline__ int waking_non_zero_trylock(struct semaphore *sem)
-{
- unsigned long flags;
- int ret = 1;
-
- spin_lock_irqsave(&semaphore_wake_lock, flags);
- if (sem->sleepers <= 0)
- atomic_inc(&sem->count);
- else {
- sem->sleepers--;
- ret = 0;
- }
- spin_unlock_irqrestore(&semaphore_wake_lock, flags);
- return ret;
-}
-
-DEFINE_SPINLOCK(semaphore_wake_lock);
-
-/*
- * Semaphores are implemented using a two-way counter:
- * The "count" variable is decremented for each process
- * that tries to sleep, while the "waking" variable is
- * incremented when the "up()" code goes to wake up waiting
- * processes.
- *
- * 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.
- *
- * waking_non_zero() (from asm/semaphore.h) must execute
- * atomically.
- *
- * When __up() is called, the count was negative before
- * incrementing it, and we need to wake up somebody.
- *
- * This routine adds one to the count of processes that need to
- * wake up and exit. ALL waiting processes actually wake up but
- * only the one that gets to the "waking" field first will gate
- * through and acquire the semaphore. The others will go back
- * to sleep.
- *
- * 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.
- */
-
-void __up(struct semaphore *sem)
-{
- wake_one_more(sem);
- wake_up(&sem->wait);
-}
-
-/*
- * Perform the "down" function. Return zero for semaphore acquired,
- * return negative for signalled out of the function.
- *
- * If called from __down, the return is ignored and the wait loop is
- * not interruptible. This means that a task waiting on a semaphore
- * using "down()" cannot be killed until someone does an "up()" on
- * the semaphore.
- *
- * If called from __down_interruptible, the return value gets checked
- * upon return. If the return value is negative then the task continues
- * with the negative value in the return register (it can be tested by
- * the caller).
- *
- * Either form may be used in conjunction with "up()".
- *
- */
-
-#define DOWN_VAR \
- struct task_struct *tsk = current; \
- wait_queue_t wait; \
- init_waitqueue_entry(&wait, tsk);
-
-#define DOWN_HEAD(task_state) \
- \
- \
- tsk->state = (task_state); \
- add_wait_queue(&sem->wait, &wait); \
- \
- /* \
- * Ok, we're set up. sem->count is known to be less than zero \
- * so we must wait. \
- * \
- * We can let go the lock for purposes of waiting. \
- * We re-acquire it after awaking so as to protect \
- * all semaphore operations. \
- * \
- * If "up()" is called before we call waking_non_zero() then \
- * we will catch it right away. If it is called later then \
- * we will have to go through a wakeup cycle to catch it. \
- * \
- * Multiple waiters contend for the semaphore lock to see \
- * who gets to gate through and who has to wait some more. \
- */ \
- for (;;) {
-
-#define DOWN_TAIL(task_state) \
- tsk->state = (task_state); \
- } \
- tsk->state = TASK_RUNNING; \
- remove_wait_queue(&sem->wait, &wait);
-
-void __sched __down(struct semaphore * sem)
-{
- DOWN_VAR
- DOWN_HEAD(TASK_UNINTERRUPTIBLE)
- if (waking_non_zero(sem))
- break;
- schedule();
- DOWN_TAIL(TASK_UNINTERRUPTIBLE)
-}
-
-int __sched __down_interruptible(struct semaphore * sem)
-{
- int ret = 0;
- DOWN_VAR
- DOWN_HEAD(TASK_INTERRUPTIBLE)
-
- ret = waking_non_zero_interruptible(sem, tsk);
- if (ret)
- {
- if (ret == 1)
- /* ret != 0 only if we get interrupted -arca */
- ret = 0;
- break;
- }
- schedule();
- DOWN_TAIL(TASK_INTERRUPTIBLE)
- return ret;
-}
-
-int __down_trylock(struct semaphore * sem)
-{
- return waking_non_zero_trylock(sem);
-}
diff --git a/arch/xtensa/kernel/xtensa_ksyms.c b/arch/xtensa/kernel/xtensa_ksyms.c
index 60dbdb43fb4c..6e52cdd6166f 100644
--- a/arch/xtensa/kernel/xtensa_ksyms.c
+++ b/arch/xtensa/kernel/xtensa_ksyms.c
@@ -26,7 +26,6 @@
#include <asm/io.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
-#include <asm/semaphore.h>
#ifdef CONFIG_BLK_DEV_FD
#include <asm/floppy.h>
#endif
@@ -71,14 +70,6 @@ EXPORT_SYMBOL(__umodsi3);
EXPORT_SYMBOL(__udivdi3);
EXPORT_SYMBOL(__umoddi3);
-/*
- * Semaphore operations
- */
-EXPORT_SYMBOL(__down);
-EXPORT_SYMBOL(__down_interruptible);
-EXPORT_SYMBOL(__down_trylock);
-EXPORT_SYMBOL(__up);
-
#ifdef CONFIG_NET
/*
* Networking support