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>

3 files changed, 1 insertions, 108 deletions

diff --git a/arch/parisc/kernel/Makefile b/arch/parisc/kernel/Makefile
index 27827bc3717e..1f6585a56f97 100644
--- a/arch/parisc/kernel/Makefile
+++ b/arch/parisc/kernel/Makefile
@@ -9,7 +9,7 @@ AFLAGS_pacache.o := -traditional
 
 obj-y           := cache.o pacache.o setup.o traps.o time.o irq.o \
                    pa7300lc.o syscall.o entry.o sys_parisc.o firmware.o \
-                   ptrace.o hardware.o inventory.o drivers.o semaphore.o \
+                   ptrace.o hardware.o inventory.o drivers.o \
                    signal.o hpmc.o real2.o parisc_ksyms.o unaligned.o \
                    process.o processor.o pdc_cons.o pdc_chassis.o unwind.o \
                    topology.o
diff --git a/arch/parisc/kernel/parisc_ksyms.c b/arch/parisc/kernel/parisc_ksyms.c
index 7aca704e96f0..5b7fc4aa044d 100644
--- a/arch/parisc/kernel/parisc_ksyms.c
+++ b/arch/parisc/kernel/parisc_ksyms.c
@@ -69,11 +69,6 @@ EXPORT_SYMBOL(memcpy_toio);
 EXPORT_SYMBOL(memcpy_fromio);
 EXPORT_SYMBOL(memset_io);
 
-#include <asm/semaphore.h>
-EXPORT_SYMBOL(__up);
-EXPORT_SYMBOL(__down_interruptible);
-EXPORT_SYMBOL(__down);
-
 extern void $$divI(void);
 extern void $$divU(void);
 extern void $$remI(void);
diff --git a/arch/parisc/kernel/semaphore.c b/arch/parisc/kernel/semaphore.c
deleted file mode 100644
index ee806bcc3726..000000000000
--- a/arch/parisc/kernel/semaphore.c
+++ /dev/null
@@ -1,102 +0,0 @@
-/*
- * Semaphore implementation Copyright (c) 2001 Matthew Wilcox, Hewlett-Packard
- */
-
-#include <linux/sched.h>
-#include <linux/spinlock.h>
-#include <linux/errno.h>
-#include <linux/init.h>
-
-/*
- * Semaphores are complex as we wish to avoid using two variables.
- * `count' has multiple roles, depending on its value.  If it is positive
- * or zero, there are no waiters.  The functions here will never be
- * called; see <asm/semaphore.h>
- *
- * When count is -1 it indicates there is at least one task waiting
- * for the semaphore.
- *
- * When count is less than that, there are '- count - 1' wakeups
- * pending.  ie if it has value -3, there are 2 wakeups pending.
- *
- * 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)
-{
-        sem->count--;
-        wake_up(&sem->wait);
-}
-
-#define wakers(count) (-1 - count)
-
-#define DOWN_HEAD                                                       \
-        int ret = 0;                                                    \
-        DECLARE_WAITQUEUE(wait, current);                               \
-                                                                        \
-        /* Note that someone is waiting */                              \
-        if (sem->count == 0)                                            \
-                sem->count = -1;                                        \
-                                                                        \
-        /* protected by the sentry still -- use unlocked version */     \
-        wait.flags = WQ_FLAG_EXCLUSIVE;                                 \
-        __add_wait_queue_tail(&sem->wait, &wait);                       \
- lost_race:                                                             \
-        spin_unlock_irq(&sem->sentry);                                  \
-
-#define DOWN_TAIL                                                       \
-        spin_lock_irq(&sem->sentry);                                    \
-        if (wakers(sem->count) == 0 && ret == 0)                        \
-                goto lost_race; /* Someone stole our wakeup */          \
-        __remove_wait_queue(&sem->wait, &wait);                         \
-        current->state = TASK_RUNNING;                                  \
-        if (!waitqueue_active(&sem->wait) && (sem->count < 0))          \
-                sem->count = wakers(sem->count);
-
-#define UPDATE_COUNT                                                    \
-        sem->count += (sem->count < 0) ? 1 : - 1;
-        
-
-void __sched __down(struct semaphore * sem)
-{
-        DOWN_HEAD
-
-        for(;;) {
-                set_task_state(current, TASK_UNINTERRUPTIBLE);
-                /* we can _read_ this without the sentry */
-                if (sem->count != -1)
-                        break;
-                schedule();
-        }
-
-        DOWN_TAIL
-        UPDATE_COUNT
-}
-
-int __sched __down_interruptible(struct semaphore * sem)
-{
-        DOWN_HEAD
-
-        for(;;) {
-                set_task_state(current, TASK_INTERRUPTIBLE);
-                /* we can _read_ this without the sentry */
-                if (sem->count != -1)
-                        break;
-
-                if (signal_pending(current)) {
-                        ret = -EINTR;
-                        break;
-                }
-                schedule();
-        }
-
-        DOWN_TAIL
-
-        if (!ret) {
-                UPDATE_COUNT
-        }
-
-        return ret;
-}